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Hureau C.,CNRS Coordination Chemistry | Hureau C.,National Polytechnic Institute of Toulouse | Dorlet P.,French National Center for Scientific Research | Dorlet P.,CEA Saclay Nuclear Research Center
Coordination Chemistry Reviews | Year: 2012

Copper ions have been proposed to play a central role in the amyloid cascade process linked to the development of Alzheimer disease (AD). Involvement in both the amyloid-β (Aβ) aggregation process and reactive oxygen species (ROS) production has been considered. In the last 15 years, many studies regarding copper(II) coordination to Aβ have been reported with divergent conclusions and a consensual binding scheme is not reached yet. They include (i) spectroscopic and thermodynamic investigations of copper(II) coordination to chemically modified peptides (mutants, truncated peptides, etc.) and subsequent analysis of the differences obtained with the native Aβ peptide; (ii) spectroscopic characterization of copper(II) coordination to Aβ via direct methods, such as advanced EPR techniques and FTIR spectroscopy combined with the use of 13C, 15N specifically labeled peptides and NMR. More recently, copper(II) coordination to naturally occurring modified peptides of biological relevance such as murine Aβ, H6R and A2V mutants, and truncated forms at position 3, have also been studied.In the present review, the objective is to give a report as exhaustive as possible of the literature structural data on copper(II) binding to the Aβ peptides and to its modified forms and to sort out contradicting results. Such discrepancies are mainly due to the unstructured nature of the copper binding site in Aβ. Concomitantly, copper(II) coordination has been revealed to be highly dynamic with equilibrium between amino-acid residues of identical nature for one binding position. As a direct consequence, the copper(II) coordination spheres proposed represent the most reasonable models obtained with data available at present. At physiological pH, two copper(II) binding sites, noted components I and II, coexist. The transition between I and II is pH-driven and the pH where the two components are found in a 1:1 ratio (pK a(I/II)) is approx. 7.8, with I (resp. II) predominant at lower (resp. higher) pH. In I and II, the equatorial binding sites of copper(II) are {NH 2 (Asp1), CO (Asp1-Ala2), N τ im (His6), N π im (His13 or His14)} and {NH 2 (Asp1), N - (Asp1-Ala2), CO (Ala2-Glu3), N τ im (His6) or N im (His13 or His14)}, respectively. I and II were clearly (and by consensus) identified by their EPR parameters, g //=2.27±0.01, A //=183±5×10 -4cm -1 and g //=2.23±0.01, A //=160±5×10 -4cm -1, respectively. Given examples of copper(II) binding to other naturally occurring Aβ peptides include binding to the murine Aβ peptide, differing from the human Aβ by three point mutations, and to the H6R mutant. Copper(II) binding to murine and human Aβ peptides diverges by the pK a(I/II) value (approx. 6.2 for the former instead of 7.8) and by the nature of the peptide functional group which undergoes deprotonation between I and II, i.e. the Gly5-His6 bond compared with the Asp1-Ala2 bond in the human case. Copper(II) binding to the H6R mutant is characterized by a pK a(I/II) value of approx. 7.3, a decrease induced by the unfavorable coordination of both His13 and His14 in component I. © 2012 Elsevier B.V. Source


Safa H.,CEA Saclay Nuclear Research Center
International Journal of Electrical Power and Energy Systems | Year: 2012

The thermodynamic efficiency of a standard Nuclear Power Plant (NPP) is around 33%. Therefore, about two third of the heat generated by the nuclear fuel is literally wasted in the environment. Given the fact that the steam coming out from the high pressure turbine is superheated, it could be advantageously used for nonelectrical applications, particularly for district heating. Considering the technological improvements achieved these last years in heat piping insulation, it is now perfectly feasible to envisage heat transport over quite long distances, exceeding 200 km, with affordable losses. Therefore, it could be energetically wise to revise the modifications required on present reactors to perform heat extraction without impeding the NPP operation. In this paper, the case of a French reactor is studied showing that a large fraction of the wasted nuclear heat can be actually recovered and transported to be injected in the heat distribution network of a large city. Some technical and economical aspects of nuclear district heating application are also discussed. © 2012 Elsevier Ltd. All rights reserved. Source


Sanchez R.,CEA Saclay Nuclear Research Center
Nuclear Engineering and Technology | Year: 2012

The point we made in this paper is that, although detailed and precise three-dimensional (3D) whole-core transport calculations may be obtained in the future with massively parallel computers, they would have an application to only some of the problems of the nuclear industry, more precisely those regarding multiphysics or for methodology validation or nuclear safety calculations. On the other hand, typical design reactor cycle calculations comprising many one-point core calculations can have very strict constraints in computing time and will not directly benefit from the advances in computations in large scale computers. Consequently, in this paper we review some of the deterministic 3D transport methods which in the very near future may have potential for industrial applications and, even with low-order approximations such as a low resolution in energy, might represent an advantage as compared with present industrial methodology, for which one of the main approximations is due to power reconstruction. These methods comprise the response-matrix method and methods based on the two-dimensional (2D) method of characteristics, such as the fusion method. Source


Marion L.F.,CEA Saclay Nuclear Research Center | Monnet I.,CNRS Center for Research on Ions, Materials and Photonics
Journal of Nuclear Materials | Year: 2013

The good radiation resistance of Ti3(Si1-xAl x)C2 (x = 0.05, 0.07, 0.1) has been recently demonstrated through 95 MeV Xe irradiations up to 2 × 1019 m-2 which did not induce amorphisation. In this work, the irradiation damage level of Ti3(Si0.95Al0.05)C2 was raised up to 4.5 × 1019 m-2: saturation of hardness above 1019 cm-2 suggests saturation of microstructure disorder. Same conclusions could be deduced from irradiation of (Ti0.95Zr 0.05)(Si0.9Al0.1)C2. © 2012 Elsevier B.V. All rights reserved. Source


Ribis J.,CEA Saclay Nuclear Research Center
Journal of Nuclear Materials | Year: 2013

The MA957 alloy has been irradiated in the french Phenix reactor at 412 °C up to 50 dpa and at 430 °C up to 75 dpa. For both irradiation conditions, the evolution of the matrix after neutron irradiation has been investigated by transmission electron microscopy especially focusing on the creation of structural defect as the dislocation loops and on the chemical evolution of the matrix. Some loops have been investigated and are found to be 〈100〉{1 0 0} interstitial type loops. Further, it is shown that the largest Ti-rich particles start to dissolve and release in the surrounding matrix their component elements. Those elements could segregate to the grain boundary. Both irradiation conditions systematically lead to the formation of α′ nano-cluster and Cr depletion at grain boundary. © 2012 Elsevier B.V. All rights reserved. Source


Simenel C.,Australian National University | Simenel C.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2010

A particle-number projection technique is used to calculate transfer probabilities in the O16+Pb208 reaction below the fusion barrier. The time evolution of the many-body wave function is obtained with the time-dependent Hartree-Fock (TDHF) mean-field theory. The agreement with experimental data for the sum of the proton-transfer channels is good, considering that TDHF has no parameter adjusted on the reaction mechanism. Some perspectives for extensions beyond TDHF to include cluster transfers are discussed. © 2010 The American Physical Society. Source


Teixeira J.,CEA Saclay Nuclear Research Center
Molecular Physics | Year: 2012

Liquid water, the most familiar liquid, is still not completely understood, even less so all the processes in which it participates. The directionality of the bonds and quantum aspects make the establishment of a complete theory difficult, particularly in the case of effective potentials built with spherical electrostatic forces. Recent work has focused on the hydrogen bonds formed between water molecules or with hydrophilic substrates. We describe the present situation of research concerning the so-called anomalies of liquid water at low temperature. Although without direct applications, this problem is consistently an object of discussion, enhanced by results from molecular dynamics simulations. Conversely, because in many situations where water plays a major role, such as, for example, in biology, only a few molecules are involved, the study of confined water is extremely important, sometimes decoupled from the more fundamental studies of bulk water. A short, but far from exclusive, summary of some of the more active domains of research concerning liquid water is given, mainly concerning interactions with other media. © 2012 Copyright Taylor and Francis Group, LLC. Source


Grappin R.,University Paris Diderot | Grappin R.,Ecole Polytechnique - Palaiseau | Pinto R.,CEA Saclay Nuclear Research Center | Velli M.,Jet Propulsion Laboratory
Astrophysical Journal Letters | Year: 2012

We present a mechanism for the formation of the low-frequency 1/f magnetic spectrum based on numerical solutions of a shell-reduced MHD model of the turbulent dynamics inside the sub-Alfvénic solar wind. We assign reasonably realistic profiles to the wind speed and the density along the radial direction, and a radial magnetic field. Alfvén waves of short periodicity (600 s) are injected at the base of the chromosphere, penetrate into the corona, and are partially reflected, thus triggering a turbulent cascade. The cascade is strong for the reflected wave while it is weak for the outward propagating waves. Reflection at the transition region recycles the strong turbulent spectrum into the outward weak spectrum, which is advected beyond the Alfvénic critical point without substantial evolution. There, the magnetic field has a perpendicular power-law spectrum with slope close to the Kolmogorov -5/3. The parallel spectrum is inherited from the frequency spectrum of large (perpendicular) eddies. The shape is a double power law with slopes of ≃ - 1 and -2 at low and high frequencies, respectively, with the position of the break depending on the injected spectrum. We suggest that the double power-law spectrum measured by Helios at 0.3AU, where the average magnetic field is not aligned with the radial (contrary to our assumptions), results from the combination of such different spectral slopes. At low frequency the parallel spectrum dominates with its characteristic 1/f shape, while at higher frequencies its steep spectral slope (-2) is masked by the more energetic perpendicular spectrum (slope -5/3). © 2012. The American Astronomical Society. All rights reserved. Source


Solon A.P.,University Paris Diderot | Chate H.,CEA Saclay Nuclear Research Center | Chate H.,University Pierre and Marie Curie | Chate H.,Beijing Computational Science Research Center | Tailleur J.,University Paris Diderot
Physical Review Letters | Year: 2015

We show that the flocking transition in the Vicsek model is best understood as a liquid-gas transition, rather than an order-disorder one. The full phase separation observed in flocking models with Z2 rotational symmetry is, however, replaced by a microphase separation leading to a smectic arrangement of traveling ordered bands. Remarkably, continuous deterministic descriptions do not account for this difference, which is only recovered at the fluctuating hydrodynamics level. Scalar and vectorial order parameters indeed produce different types of number fluctuations, which we show to be essential in selecting the inhomogeneous patterns. This highlights an unexpected role of fluctuations in the selection of flock shapes. © 2015 American Physical Society. Source


Dias O.J.C.,CEA Saclay Nuclear Research Center | Horowitz G.T.,University of California at Santa Barbara | Marolf D.,University of California at Santa Barbara | Santos J.E.,University of California at Santa Barbara
Classical and Quantum Gravity | Year: 2012

Despite the recent evidence that anti-de Sitter (AdS) spacetime is nonlinearly unstable, we argue that many asymptotically AdS solutions are nonlinearly stable. This includes geons, boson stars and black holes. As part of our argument, we calculate the frequencies of long-lived gravitational quasinormal modes of AdS black holes in various dimensions. We also discuss a new class of asymptotically AdS solutions describing noncoalescing black hole binaries. © 2012 IOP Publishing Ltd. Source


Massai S.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2012

We construct an M-theory background dual to the metastable state recently discussed by Klebanov and Pufu, which corresponds to placing a stack of anti-M2 branes at the tip of a warped Stenzel space. With this purpose we analytically solve for the linearized non-supersymmetric deformations around the warped Stenzel space, preserving the SO(5) symmetries of the supersymmetric background, and which interpolate between the IR and UV region. We identify the supergravity solution which corresponds to a stack of N̄ backreacting anti-M2 branes by fixing all the 12 integration constants in terms of N̄. While in the UV this solution has the desired features to describe the conjectured metastable state of the dual (2+1)-dimensional theory, in the IR it suffers from a singularity in the four-form ux, which we describe in some details. © SISSA 2012. Source


Blaizot J.-P.,CEA Saclay Nuclear Research Center
Lecture Notes in Physics | Year: 2012

These lectures are centered around a specific problem, the effect of weak repulsive interactions on the transition temperature of a Bose gas. This problem provides indeed a beautiful illustration of many of the techniques which have been discussed at this school on effective theories and renormalization group. Effective theories are used first in order to obtain a simple hamiltonian describing the atomic interactions: because the typical atomic interaction potentials are short range, and the systems that we consider are dilute, these potentials can be replaced by a contact interaction whose strength is determined by the -wave scattering length. Effective theories are used next in order to obtain a simple formula for the shift in : this comes from the fact that near the physics is dominated by low momentum modes whose dynamics is most economically described in terms of classical fields. The ingredients needed to calculate the shift of can be obtained from this classical field theory. Finally the renormalization group is used both to obtain a qualitative understanding, and also as a non perturbative tool to evaluate quantitatively the shift in . © 2012 Springer-Verlag Berlin Heidelberg. Source


Duguet T.,CEA Saclay Nuclear Research Center | Duguet T.,Michigan State University | Hagen G.,Oak Ridge National Laboratory | Hagen G.,University of Tennessee at Knoxville
Physical Review C - Nuclear Physics | Year: 2012

The present work discusses, from an ab initio standpoint, the definition, the meaning, and the usefulness of effective single-particle energies (ESPEs) in doubly closed shell nuclei. We perform coupled-cluster calculations to quantify to what extent selected closed-shell nuclei in the oxygen and calcium isotopic chains can effectively be mapped onto an effective independent-particle picture. To do so, we revisit in detail the notion of ESPEs in the context of strongly correlated many-nucleon systems and illustrate the necessity of extracting ESPEs through the diagonalization of the centroid matrix, as originally argued by Baranger. For the purpose of illustration, we analyze the impact of correlations on observable one-nucleon separation energies and nonobservable ESPEs in selected closed-shell oxygen and calcium isotopes. We then state and illustrate the nonobservability of ESPEs. Similarly to spectroscopic factors, ESPEs can indeed be modified by a redefinition of inaccessible quantities while leaving actual observables unchanged. This leads to the absolute necessity of employing consistent structure and reaction models based on the same nuclear Hamiltonian to extract the shell structure in a meaningful fashion from experimental data. © 2012 American Physical Society. Source


Theodoulidis T.,University of Western Macedonia | Skarlatos A.,CEA Saclay Nuclear Research Center
IEEE Transactions on Magnetics | Year: 2012

We present a development on an existing model for the electromagnetic interaction of a coil with a conductive cylinder. We can now calculate analytically both the electromagnetic field and the impedance of arbitrarily positioned probe coils. This is possible by using an appropriate expansion of cylindrical eigenfunctions in terms of eigenfunctions of the Cartesian coordinate system. The extended model is useful in simulating eddy current inspections of cylindrical structures under conditions of probe tilt as well as inspections with special coil orientations like the rotating probe coil. © 2012 IEEE. Source


Chowdhury B.D.,University of Amsterdam | Vercnocke B.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2012

We search for stable bound states of non-extremal rotating three-charge black holes in five dimensions (Cvetic-Youm black holes) and supertubes. We do this by studying the potential of supertube probes in the non-extremal black hole background and find that generically the marginally bound state of the supersymmetric limit becomes metastable and disappears with non-extremality (higher temperature). However near extremality there is a range of parameters allowing for stable bound states, which have lower energy than the supertube-black hole merger. Angular momentum is crucial for this effect. We use this setup in the D1-D5 decoupling limit to map a thermodynamic instability of the CFT (a new phase which is entropically dominant over the black hole phase) to a tunneling instability of the black hole towards the supertube-black hole bound state. This generalizes the results of [1], which mapped an entropy enigma in the bulk to the dual CFT in a supersymmetric setup. Source


Van Riet T.,CEA Saclay Nuclear Research Center
Classical and Quantum Gravity | Year: 2012

We derive necessary criteria for the existence of classical meta-stable de Sitter solutions in flux compactifications of type II supergravity down to dimensions higher than 4. We find that the possibilities in higher dimensions are much more restricted than in four dimensions. The only models that satisfy the criteria are derived from O6 compactifications to D = 5, 6 and O5 compactifications to D = 5, and no meta-stable solutions can exist in dimensions higher than 6. All these models have in common that the compact dimensions are negatively curved. © 2012 IOP Publishing Ltd. Source


Deliot F.,CEA Saclay Nuclear Research Center | Glenzinski D.A.,Fermi National Accelerator Laboratory
Reviews of Modern Physics | Year: 2012

The field of top-quark physics is reviewed using tt̄ events with an emphasis on experimental techniques. The role of the top quark in the standard model of particle physics is summarized and the basic phenomenology of top-quark production and decay is introduced. Contributions from physics beyond the standard model could affect the top-quark properties or event samples. The many measurements made at the Fermilab Tevatron, which test the standard model predictions or probe for direct evidence of new physics using the top-quark event samples, are reviewed here. © 2012 American Physical Society. Source


Politopoulos I.,CEA Saclay Nuclear Research Center
Earthquake Engineering and Structural Dynamics | Year: 2010

In this paper, the origin of rocking-type excitations and their effects on the response of base isolated structures are studied. In particular, the role of kinematic interaction in the determination of the rocking excitation is highlighted. The cases of surface foundations subjected to horizontally propagating waves, as well as of embedded foundations under vertically incident shear waves are examined. The validity of the kinematic interaction based on the rigid base mat assumption is discussed. It is shown that, in the case of classical horizontal isolation, rocking input may amplify significantly the response of the lower non-isolated modes. The examination of full three-dimensional isolation and active and semi-active control methods demonstrates the efficacy of these methods to improve the performance of seismically isolated structures subjected to rocking excitations. Copyright © 2009 John Wiley & Sons, Ltd. Source


Levy A.,Tel Aviv University | Andelman D.,Tel Aviv University | Orland H.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2012

We study the variation of the dielectric response of a dielectric liquid (e.g. water) when a salt is added to the solution. Employing field-theoretical methods, we expand the Gibbs free energy to first order in a loop expansion and calculate self-consistently the dielectric constant. We predict analytically the dielectric decrement which depends on the ionic strength in a complex way. Furthermore, a qualitative description of the hydration shell is found and is characterized by a single length scale. Our prediction fits rather well a large range of concentrations for different salts using only one fit parameter related to the size of ions and dipoles. © 2012 American Physical Society. Source


Bertuzzo E.,CEA Saclay Nuclear Research Center | Frugiuele C.,Carleton University
Journal of High Energy Physics | Year: 2012

We study neutrino physics in the context of a supersymmetric model where a continuous R-symmetry is identified with the total Lepton Number and one sneutrino can thus play the role of the down type Higgs. We show that R-breaking effiects communicated to the visible sector by Anomaly Mediation can reproduce neutrino masses and mixing solely via radiative contributions, without requiring any additional degree of freedom. In particular, a relatively large reactor angle (as recently observed by the Daya Bay collaboration) can be accommodated in ample regions of the parameter space. On the contrary, if the R-breaking is communicated to the visible sector by gravitational effects at the Planck scale, additional particles are necessary to accommodate neutrino data. Source


Zaehle S.,Max Planck Institute for Biogeochemistry | Friedlingstein P.,University of Bristol | Friedlingstein P.,CEA Saclay Nuclear Research Center | Friend A.D.,University of Cambridge
Geophysical Research Letters | Year: 2010

The effects of nitrogen (N) constraints on future terrestrial carbon (C) dynamics are investigated using the O-CN land surface model. The model's responses to elevated [CO2] and soil warming agree well with observations made in ecosystem manipulation studies. N dynamics reduce terrestrial C storage due to CO2 fertilization over the period 1860-2100 by ∼50% (342 Pg C) mainly in mid-high latitude ecosystems, compared to a simulation not accounting for N dynamics. Conversely, N dynamics reduce projected losses of land C due to increasing temperature by 16% (49 Pg C); however, this effect is prevalent only in mid-high latitude ecosystems. Despite synergistic interactions, the balance of these opposing effects is a significant reduction in future net land C storage. Terrestrial N dynamics thereby consistently increase atmospheric [CO2] in the year 2100 with a median value of 48 (41-55) ppmv, corresponding to an additional radiative forcing of 0.29 (0.28-0.34) W m-2. Copyright 2010 by the American Geophysical Union. Source


Sticlet D.,University Paris - Sud | Bena C.,University Paris - Sud | Bena C.,CEA Saclay Nuclear Research Center | Simon P.,University Paris - Sud
Physical Review Letters | Year: 2012

We study a one-dimensional wire with strong Rashba and Dresselhaus spin-orbit coupling (SOC), which supports Majorana fermions when subject to a Zeeman magnetic field and in the proximity of a superconductor. Using both analytical and numerical techniques we calculate the electronic spin texture of the Majorana end states. We find that the spin polarization of these states depends on the relative magnitude of the Rashba and Dresselhaus SOC components. Moreover, we define and calculate a local "Majorana polarization" and "Majorana density" and argue that they can be used as order parameters to characterize the topological transition between the trivial system and the system exhibiting Majorana bound modes. We find that the local Majorana polarization is correlated to the transverse spin polarization, and we propose to test the presence of Majorana fermions in a 1D system by a spin-polarized density of states measurement. © 2012 American Physical Society. Source


Schenck E.,CEA Saclay Nuclear Research Center
Communications in Mathematical Physics | Year: 2010

We establish the presence of a spectral gap near the real axis for the damped wave equation on a manifold with negative curvature. This result holds under a dynamical condition expressed by the negativity of a topological pressure with respect to the geodesic flow. As an application, we show an exponential decay of the energy for all initial data sufficiently regular. This decay is governed by the imaginary part of a finite number of eigenvalues close to the real axis. © 2010 Springer-Verlag. Source


Gaffet B.,CEA Saclay Nuclear Research Center
Journal of Physics A: Mathematical and Theoretical | Year: 2010

We consider Dyson's model (Dyson F J 1968 J. Math. Mech. 18 91) of an ellipsoidally stratified ideal gas cloud expanding adiabatically into a vacuum, in the Liouville integrable case where the gas is monatomic (γ = 5/3) and there is no vorticity (Gaffet B 2001a J. Phys. A: Math. Gen. 34 2097; Paper I). In the cases of rotation about a fixed axis the separation of variables can be achieved, and the separable variables are linearly related to a set of three variables denoted by ρ, R, W (Gaffet B 2001b J. Phys. A: Math. Gen. 34 9195; Paper II). We show in the present work that these variables admit a natural generalization to cases of rotation about a movable axis (precessing motion). The present study is restricted to the consideration of the so-called degenerate cases (see Gaffet B 2006 J. Phys. A: Math. Gen. 39 99; Paper III), but we hope to generalize our results in the future to the non-degenerate ones as well. We also present a new, compact and generally valid formulation of one of the integrals of motion, of the sixth degree in the momenta, denoted by I 6. © 2010 IOP Publishing Ltd. Source


Cherhal F.,French National Institute for Agricultural Research | Cousin F.,CEA Saclay Nuclear Research Center | Capron I.,French National Institute for Agricultural Research
Langmuir | Year: 2015

Aggregation of rodlike colloidal particles is investigated here through the aggregation process by either increasing ionic strength or decreasing surface charge density of cellulose nanocrystals (CNCs). The form factor of the nanoparticles is characterized up to the Guinier plateau using small-angle neutron scattering (SANS) extended to very small scattering vector Q. Ionic strength, above the threshold of screening charges, brings aggregative conditions that induced fractal organizations for both charged and uncharged CNCs. These two structures display respective fractal dimensions of 2.1 for charged CNCs at high ionic strength and 2.3 for desulfated CNCs over more than a decade of the scattering vector Q, irrespective of salinity, revealing a denser structuration for neutral particles. This is discussed in the framework of aggregation of rodlike particles with an aspect ratio higher than 8. Furthermore, dilution of the rod gel led to disentanglement of the network of fractal aggregates with a subsequent macroscopic sedimentation of the suspensions, with a characteristic time that depends upon the ionic strength and surface charge density. It revealed a threshold independent of salt content around 2.5 g/L and the metastable out-of-equilibrium character of CNC suspensions. © 2015 American Chemical Society. Source


Mallick K.,CEA Saclay Nuclear Research Center
Journal of Statistical Mechanics: Theory and Experiment | Year: 2011

The asymmetric simple exclusion process (ASEP) is a paradigm for non-equilibrium physics that appears as a building block to model various lowdimensional transport phenomena, ranging from intracellular traffic to quantum dots. We review some recent results obtained for the system on a periodic ring by using the Bethe ansatz. We show that this method allows one to derive analytically many properties of the dynamics of the model such as the spectral gap and the generating function of the current. We also discuss the solution of a generalized exclusion process with N species of particles and explain how a geometric construction inspired from queuing theory sheds light on a matrix product representation technique that has been very fruitful for deriving exact results for the ASEP. © 2011 IOP Publishing Ltd and SISSA. Source


Monthus C.,CEA Saclay Nuclear Research Center
Journal of Statistical Mechanics: Theory and Experiment | Year: 2011

Filyokov and Karpov (1967 Inzh.-Fiz.Zh. 13 624) have proposed a theory of non-equilibrium steady states in direct analogy with the theory of equilibrium states: the principle is to maximize the Shannon entropy associated with the probability distribution of dynamical trajectories in the presence of constraints, including the macroscopic current of interest, via the method of Lagrange multipliers. This maximization leads directly to the generalized Gibbs distribution for the probability distribution of dynamical trajectories, and to some fluctuation relation of the integrated current. The simplest stochastic dynamics where these ideas can be applied are discrete-time Markov chains, defined by transition probabilities Wi→j between configurations i and j: instead of choosing the dynamical rules Wi→j a priori, one determines the transition probabilities and the associate stationary state that maximize the entropy of dynamical trajectories with the other physical constraints that one wishes to impose. We give a self-contained and unified presentation of this type of approach, both for discrete-time Markov chains and for continuous-time master equations. The obtained results are in full agreement with the Bayesian approach introduced by Evans (2004 Phys.Rev.Lett.92150601) under the name 'Non-equilibrium Counterpart to detailed balance', and with the 'invariant quantities' derived by Baule and Evans (2008 Phys.Rev.Lett.101 240601), but provide a slightly different perspective via the formulation in terms of an eigenvalue problem. © 2011 IOP Publishing Ltd and SISSA. Source


Poyet S.,CEA Saclay Nuclear Research Center
Cement and Concrete Research | Year: 2016

A simple, analytical model was proposed to account for the effect of moderate temperature on water retention in cement-based materials. The model takes advantage of the simplicity and flexibility of van Genuchten equation. It was first calibrated using experimental results taken from literature and then successfully validated on other results. The presented model provides a valuable tool for the description of water transport in unsaturated cementitious materials submitted to moderate temperatures (up to 85 °C). © 2016 Elsevier Ltd. All rights reserved. Source


Thuery P.,CEA Saclay Nuclear Research Center | Masci B.,University of Rome La Sapienza | Harrowfield J.,CNRS Institute of Science and Supramolecular Engineering
Crystal Growth and Design | Year: 2013

The reaction of uranyl and rare-earth nitrates with 4,4′-(1,1,1,3,3, 3-hexafluoroisopropylidene)diphthalic acid (H4L) under hydro-/solvo-thermal conditions (2:1 water/acetonitrile at 180 C) gives a series of complexes, most of which have been crystallographically characterized. In the lattice of the uranyl complex [(UO2)2(L)(H 2O)2]·2H2O (1), the metal atoms are chelated by two adjacent carboxylate groups, each of the latter being bridging bidentate, and the resulting coordination polymer is two-dimensional. The ∼14 Å thick layers comprise two uranyl-covered faces linked to one another by L4- pillars, a claylike architecture likely due to the hydrophobic interactions between the organic ligands. The complexes [Ce(HL)(H2O)]·1.5H2O (2) and [Nd(HL)(H 2O)]·2.5H2O (3) are isomorphous and they display a high degree of connectivity, with the metal atoms in ten- or eleven-coordinate environments being bound to five or six HL3- ligands. The three-dimensional (3D) framework formed contains one-dimensional subunits of adjacent metal ions with each coordination polyhedron sharing two triangular faces with its neighbors. The hydrophobic CF3 groups are oriented divergently from the exterior of wide channels (∼22 × 8 Å), which are occupied by the solvent water molecules. The complexes with rare-earth ions of smaller ionic radii, [M4(L)3(H2O) 9]·7H2O with M = Er (4), Yb (5), and Y (6), are isomorphous to the previously reported terbium(III) complex, and they crystallize as 3D frameworks containing di- and tetra-nuclear subunits. In the visible region, only the uranyl and europium (and terbium) complexes display significant solid-state luminescence. © 2013 American Chemical Society. Source


Alexandrov D.V.,Ural Federal University | Nizovtseva G.,CEA Saclay Nuclear Research Center
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2014

An exact analytical solution of an integro-differential model describing the transient nucleation of solid particles (nuclei) and their growth with fluctuating rates at the intermediate stage of bulk phase transitions in metastable systems is constructed. Two important cases of the Weber-Volmer-Frenkel-Zel'dovich and Mier nucleation kinetics are detailed for supercooled melts and supersaturated solutions. © 2013 The Author(s) Published by the Royal Society. All rights reserved. Source


Torres M.A.C.,CEA Saclay Nuclear Research Center
European Physical Journal C | Year: 2014

We study the cluster algebra of the kinematic configuration space Confn(ℙ3) of an n-particle scattering amplitude restricted to the special 2D kinematics. We found that the n-point two-loop MHV remainder function in special 2D kinematics depends on a selection of the X-coordinates that are part of a special structure of the cluster algebra related to snake triangulations of polygons. This structure forms a necklace of hypercube beads in the corresponding Stasheff polytope. Furthermore at n = 12, the cluster algebra and the selection of the X-coordinates in special 2D kinematics replicates the cluster algebra and the selection of X-coordinates of the n = 6 two-loop MHV amplitude in 4D kinematics. © 2014 The Author(s). Source


Krieger-Liszkay A.,CEA Saclay Nuclear Research Center | Kos P.B.,Hungarian Academy of Sciences | Hideg E.,Hungarian Academy of Sciences
Physiologia Plantarum | Year: 2011

The effect of superoxide anion radicals on the photosynthetic electron transport chain was studied in leaves and isolated thylakoids from tobacco. Superoxide was generated by methylviologen (MV) in the light at the acceptor side of photosystem I (PSI). In isolated thylakoids, the largest damage was observed at the level of the water-splitting activity in photosystem II (PSII), whereas PSI was hardly affected at the light intensities used. Addition of reactive oxygen scavengers protected PSII against damage. In leaves in the presence of MV, the quantum yield of PSII decreased during illumination whereas the size of the P700 signal remained constant. There was no D1 protein loss in leaves illuminated in the presence of MV and lincomycin, but a modification to a slightly higher molecular mass was observed. These data show that PSII is more sensitive to superoxide or superoxide-derived reactive oxygen species (ROS) than PSI. In our experiments, this susceptibility was not because of any action of the ROS on the translation of the D1 protein or on the repair cycle of photosystem. © Physiologia Plantarum 2010. Source


Galaasen E.V.,University of Bergen | Ninnemann U.S.,University of Bergen | Irvali N.,University of Bergen | Kleiven H.F.,University of Bergen | And 3 more authors.
Science | Year: 2014

Deep ocean circulation has been considered relatively stable during interglacial periods, yet little is known about its behavior on submillennial time scales. Using a subcentennially resolved epibenthic foraminiferal δ13C record, we show that the influence of North Atlantic Deep Water (NADW) was strong at the onset of the last interglacial period and was then interrupted by several prominent centennial-scale reductions. These NADW transients occurred during periods of increased ice rafting and southward expansions of polar water influence, suggesting that a buoyancy threshold for convective instability was triggered by freshwater and circum-Arctic cryosphere changes. The deep Atlantic chemical changes were similar in magnitude to those associated with glaciations, implying that the canonical view of a relatively stable interglacial circulation may not hold for conditions warmer and fresher than at present. Source


Sausset F.,CEA Saclay Nuclear Research Center | Tarjus G.,French National Center for Scientific Research
Physical Review Letters | Year: 2010

We investigate the characteristic length scales associated with the glass transition phenomenon. By studying an atomic glass-forming liquid in negatively curved space, for which the local order is well identified and the amount of frustration opposing the spatial extension of this order is tunable, we provide insight into the structural origin of the main characteristics of the dynamics leading to glass formation. We find that the structural length and the correlation length characterizing the increasing heterogeneity of the dynamics grow together as temperature decreases. However, the system eventually enters a regime in which the former saturates as a result of frustration whereas dynamic correlations keep building up. © 2010 The American Physical Society. Source


Gouillart E.,Saint - Gobain | Thiffeault J.-L.,University of Wisconsin - Madison | Dauchot O.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2010

We report on the decay of a passive scalar in chaotic mixing protocols where the wall of the vessel is rotated, or a net drift of fluid elements near the wall is induced at each period. As a result the fluid domain is divided into a central isolated chaotic region and a peripheral regular region. Scalar patterns obtained in experiments and simulations converge to a strange eigenmode and follow an exponential decay. This contrasts with previous experiments with a chaotic region spanning the whole domain, where fixed walls constrained mixing to follow a slower algebraic decay. Using a linear analysis of the flow close to the wall, as well as numerical simulations of Lagrangian trajectories, we study the influence of the rotation velocity of the wall on the size of the chaotic region, the approach to its bounding separatrix, and the decay rate of the scalar. © 2010 The American Physical Society. Source


Canet L.,CNRS Physics and Models in Condensed Media Laboratory | Chate H.,CEA Saclay Nuclear Research Center | Delamotte B.,University Pierre and Marie Curie | Wschebor N.,University of the Republic of Uruguay
Physical Review Letters | Year: 2010

We present a simple approximation of the nonperturbative renormalization group designed for the Kardar-Parisi-Zhang equation and show that it yields the correct phase diagram, including the strong-coupling phase with reasonable scaling exponent values in physical dimensions. We find indications of a possible qualitative change of behavior around d=4. We discuss how our approach can be systematically improved. © 2010 The American Physical Society. Source


Valageas P.,CEA Saclay Nuclear Research Center | Sato M.,Nagoya University | Nishimichi T.,University of Tokyo
Astronomy and Astrophysics | Year: 2012

Aims. We investigate the performance of an analytic model of the 3D matter distribution, which combines perturbation theory with halo models, for weak-lensing statistics. Methods. We compare our predictions for the weak-lensing convergence power spectrum and bispectrum with numerical simulations and fitting formulas proposed in previous works. Results. We find that this model provides better agreement with simulations than published fitting formulas. This shows that building on systematic and physically motivated models is a promising approach. Moreover, this makes explicit the link between the weak-lensing statistics and the underlying properties of the 3D matter distribution, as a function of scale ℓ. Thus, we obtain the contributions to the lensing power spectrum and bispectrum that arise from perturbative terms (complete up to one-loop) and nonperturbative terms (e.g., "1-halo" term). Finally, we show that this approach recovers the dependence on cosmology (for realistic scenarios). © 2012 ESO. Source


Valageas P.,CEA Saclay Nuclear Research Center | Sato M.,Nagoya University | Nishimichi T.,University of Tokyo
Astronomy and Astrophysics | Year: 2012

Aims. We investigate the performance of an analytic model of the 3D matter distribution, which combines perturbation theory with halo models, for weak-lensing configuration-space statistics. Methods. We compared our predictions for the weak-lensing convergence two-point and three-point correlation functions with numerical simulations and fitting formulas proposed in previous works. We also considered the second-and third-order moments of the smoothed convergence and of the aperture-mass. Results. As in our previous study of Fourier-space weak-lensing statistics, we find that our model agrees better with simulations than previously published fitting formulas. Moreover, we recover the dependence on cosmology of these weak-lensing statistics and we can describe multi-scale moments. This approach allows us to obtain the quantitative relationship between these integrated weak-lensing statistics and the various contributions to the underlying 3D density fluctuations, decomposed over perturbative, two-halo, or one-halo terms. © 2012 ESO. Source


Paillard D.,CEA Saclay Nuclear Research Center
Quaternary Science Reviews | Year: 2015

Ice ages are known since the mid-nineteenth century. From the beginning, they have been at the center of theories of climate and climate change. Still, the mechanisms behind these large amplitude oscillations remain poorly understood. In order to position our current knowledge of glacial-interglacial cycles, it is useful to present how the notion of climate change appeared in the XIXth century with the discovery of glacial periods, and how the two main theories, the astronomical one and the geochemical one, emerged progressively both from sound physical principles but also from extravagant ideas. Major progresses in geochemistry in the XXth century led first to the firm evidence of an astronomical pacemaker of these cycles thanks to the accumulation of paleoceanographic data. Still, the Milankovitch's theory predicts an ice age cyclicity of about 41,000 years, while the major periodicity found in the records is 100,000yr. Besides, ice cores from Antarctica proved unambiguously that the atmospheric carbon dioxide was lower during glacial periods. Even more importantly, during the last termination, the atmospheric pCO2 increases significantly by about 50ppm, several millenia before any important change in continental ice volume. This fact, together with many other pieces of information, strongly suggests an active role of greenhouse gases in the ice age problem, at least during deglaciations. Since terminations are precisely at the heart of the 100-ka problem, we need to formulate a new synthesis of the astronomical and geochemical theories in order to unravel this almost two-century-old question of ice ages. The foundations of such a theory have already been put forward, and its predictions appear in surprisingly good agreement with many recent observations. © 2014 Elsevier Ltd. Source


Valageas P.,CEA Saclay Nuclear Research Center | Clerc N.,Max Planck Institute for Extraterrestrial Physics
Astronomy and Astrophysics | Year: 2012

Context. Large ongoing and upcoming galaxy cluster surveys in the optical, X-ray and millimetric wavelengths will provide rich samples of galaxy clusters at unprecedented depths. One key observable for constraining cosmological models is the correlation function of these objects, measured through their spectroscopic redshift. Aims. We study the redshift-space correlation functions of clusters of galaxies, averaged over finite redshift intervals, and their covariance matrices. Expanding as usual the angular anisotropy of the redshift-space correlation on Legendre polynomials, we consider the redshift-space distortions of the monopole as well as the next two multipoles, 2ℓ = 2 and 4. Methods. Taking into account the Kaiser effect, we developed an analytical formalism to obtain explicit expressions of all contributions to these mean correlations and covariance matrices. We include shot-noise and sample-variance effects as well as Gaussian and non-Gaussian contributions. Results. We obtain a reasonable agreement with numerical simulations for the mean correlations and covariance matrices on large scales (r > 10 h -1 Mpc). Redshift-space distortions amplify the monopole correlation by about 10-20%, depending on the halo mass, but the signal-to-noise ratio remains of the same order as for the real-space correlation. This distortion will be significant for surveys such as DES, Erosita, and Euclid, which should also measure the quadrupole 2ℓ = 2. The third multipole, 2ℓ = 4, may only be marginally detected by Euclid. © 2012 ESO. Source


Ephritikhine M.,CEA Saclay Nuclear Research Center
Coordination Chemistry Reviews | Year: 2016

A comprehensive review of molecular actinide complexes with ligands containing soft donor chalcogen atoms (S, Se, Te), highlighting the more recent advances, is presented. © 2016 Elsevier B.V. Source


An C.S.,Southwest University | Saghai B.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Within an extended chiral constituent quark formalism, we investigate contributions from all possible five-quark components in the octet baryons to the pion-baryon (σπB) and strangeness-baryon (σsB) sigma terms: B≡N,Λ,Σ,Ξ. The probabilities of the quark-antiquark components in the ground-state baryon octet wave functions are calculated by taking the baryons to be admixtures of three- and five-quark components, with the relevant transitions handled via the P03 mechanism. Predictions for σπB and σsB obtained by using input parameters taken from the literature are reported. Our results turn out to be, in general, consistent with the findings via lattice QCD and chiral perturbation theory. © 2015 American Physical Society. Source


Ribis J.,CEA Saclay Nuclear Research Center | Lozano-Perez S.,University of Oxford
Journal of Nuclear Materials | Year: 2014

ODS steels are promising materials for Sodium cooled Fast Reactors since their fine distribution of nano-clusters confers excellent mechanical properties. However, the nano-feature stability needs to be assessed under neutron irradiation. Before irradiation, the characterizations show that nano-particles are finely distributed within the ferritic matrix and are identified to have a pyrochlore type structure. After irradiation of the MA957 alloy in the Phenix French reactor at 412 C up to 50 dpa and 430 C up to 75 dpa, transmission electron microscopy characterization reveals a very slight density fall but no distinguishable difference in nano-features size before and after irradiation. In addition, after both irradiations, the nano-oxides are still (Y, Ti, O) compounds with orientation relationship with the matrix. A multislice simulation of high resolution images suggests that nano-particles still have a fcc pyrochlore type structure after irradiation. A possible change of lattice parameter seems to be highlighted, possibly due to disordering by cascade effect. © 2013 Elsevier B.V. All rights reserved. Source


Thuery P.,CEA Saclay Nuclear Research Center | Riviere E.,University Paris - Sud
Dalton Transactions | Year: 2013

Five oxalate complexes containing both uranyl and copper(ii) ions and 2,2′-bipyridine (bipy), 2,2′-bipyrimidine (bipym) or 1,10-phenanthroline (phen) as co-ligands have been synthesized under hydrothermal conditions and their crystal structures were determined. [UO 2Cu(C2O4)(NO3)2(bipy) (H2O)] (1) is a molecular complex in which the two cations are connected by the bis-chelating oxalate. A one-dimensional uranyl oxalate ribbon is formed in [UO2Cu(C2O4)2(bipym) (H2O)] (2), with uranyl ions bound to two chelating anions and to a third, monodentate oxalate which holds the decorating [Cu(bipym)(H 2O)]2+ groups. Complex [(UO2) 2Cu2(C2O4)2(bipym) 3(OH)2]·2NO3 (3) is a two-dimensional assembly in which uranyl oxalate chains are linked to one another by [Cu 2(bipym)3]4+ dinuclear units through bridging hydroxide ions. Finally, [UO2Cu(C2O4) 2(bipy)] (4) and [UO2Cu(C2O4) 2(phen)] (5) display identical three-dimensional arrangements containing uranyl oxalate sheets connected to one another by copper oxalate dinuclear units. The magnetic properties of compounds 2 and 4 have been investigated. Weak inter-chain antiferromagnetic interactions between copper(ii) atoms are present in 2, while 4 displays strong oxalate-mediated antiferromagnetic exchange (J = -335 cm-1). These complexes are the first uranyl-d block metal oxalate complexes to be reported. © 2013 The Royal Society of Chemistry. Source


Dias O.J.C.,CEA Saclay Nuclear Research Center | Reall H.S.,University of Cambridge
Classical and Quantum Gravity | Year: 2013

We study algebraically special perturbations of a generalized Schwarzschild solution in any number of dimensions. There are two motivations. First, to learn whether there exist interesting higher-dimensional algebraically special solutions beyond the known ones. Second, algebraically special perturbations present an obstruction to the unique reconstruction of general metric perturbations from gauge-invariant variables analogous to the Teukolsky scalars and it is desirable to know the extent of this non-uniqueness. In four dimensions, our results generalize those of Couch and Newman, who found infinite families of time-dependent algebraically special perturbations. In higher dimensions, we find that the only regular algebraically special perturbations are those corresponding to deformations within the Myers-Perry family. Our results are relevant for several inequivalent definitions of 'algebraically special'. © 2013 IOP Publishing Ltd. Source


The self-assembly of the star-shaped 2,4,6-tris(4′,4″, 4‴-trimethylphenyl)-1,3,5-triazine molecule is investigated using scanning tunneling microscopy (STM) at the solid/liquid interface. This molecule self-assembles into a large-scale close-packed nanoarchitecture stabilized by van der Waals interactions on graphite. High-resolution STM images reveal intramolecular features; i.e., the molecular central ring appears brighter in the high-resolution STM images where nitrogen atoms are located. In addition, STM images show that molecules are mobile at the domain boundary when neighboring domains are aligned. In comparison, the molecular close packing is preserved at the boundary where neighboring domains are shifted. © 2014 American Chemical Society. Source


Cornaggia C.,CEA Saclay Nuclear Research Center
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2012

Laser-induced multiple ionization and Coulomb explosion of small molecules may lead on average to more than one fragmentation event per laser pulse even when experiments are performed at very low gas pressures in the 10 810 9 mbar range. In order to bypass the failure of coincidence techniques in this case, Frasinski et al (1989 Science 246 1029) proposed an alternative technique denoted covariance mapping based on correlated fluctuations of digitized ion signals coming from identical fragmentation channels. A probabilistic approach of the detected signals shows that covariance eliminates false coincidences due to fragments from different fragmentation channels, and false coincidences due to fragments from the same fragmentation channel, but which do not originate from the same unimolecular fragmentation events. The analysis is extended to devices which do not accept more than one count per time-of-flight bin such as multichannel scalers or time-to-digital converters. It is still possible to remove false coincidences using covariance but with a formulation which is noticeably different from the initial proposal for digitized signals. © 2012 IOP Publishing Ltd. Source


Dymarsky A.,Institute for Advanced Study | Kuperstein S.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2012

We find a new family of non-supersymmetric numerical solutions of IIB supergravity which are dual to the N = 1 cascading "conifold" theory perturbed by certain combinations of relevant single trace and marginal double trace operators with non innitesimal couplings. The SUSY is broken but the resulting ground states, and their gravity duals, remain stable, at least perturbatively. Despite the complicated field theory dynamics the gravity solutions have a simple structure. They feature the Ricci-flat non-Kähler metric on the deformed conifold and the imaginary self-dual three-form flux accompanied by a constant dilaton. Source


Politopoulos I.,CEA Saclay Nuclear Research Center
Journal of Earthquake Engineering | Year: 2010

In this article, the influence of nonlinear behavior of multiple degree of freedom (MDOF) primary structures on floor response spectra is investigated by means of simple structural models. The cases of shear beam type as well as of capacity-designed plane frames were studied. It is shown that, in general, but not always, nonlinearity of the primary structure has a beneficial effect on floor spectra. However, higher mode response may be amplified due to nonlinear behavior. The issue of a one story structure exhibiting torsionnal response has also been addressed and some important properties are highlighted. Copyright © A.S. Elnashai & N.N. Ambraseys. Source


Brax P.,CEA Saclay Nuclear Research Center
Acta Physica Polonica B | Year: 2012

The acceleration of the expansion of the Universe has led to the construction of Dark Energy models, where a light scalar field may have a range reaching up to cosmological scales. Screening mechanisms allow these models to evade the tight gravitational tests in the solar system and the laboratory. I will briefly review some of the salient features of screened modified gravity models of the chameleon, dilaton or symmetron types using f(R) gravity as a template. Source


Gehrmann-De Ridder A.,ETH Zurich | Gehrmann T.,University of Zurich | Ritzmann M.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2012

The antenna subtraction method handles real radiation contributions in higher order corrections to jet observables. The method is based on antenna functions, which encapsulate all unresolved radiation between a pair of hard radiator partons. To apply this method to compute hadron collider observables, initial-initial antenna functions with both radiators in the initial state are required in unintegrated and integrated forms. In view of extending the antenna subtraction method to next-to-next-to-leading order (NNLO) calculations at hadron colliders, we derive the full set of initial-initial double real radiation antenna functions in integrated form. Source


Chevallier F.,CEA Saclay Nuclear Research Center | O'Dell C.W.,Colorado State University
Geophysical Research Letters | Year: 2013

Statistical modeling is at the root of CO2 atmospheric inversion systems, but few studies have focused on the quality of their assigned probability distributions. In this paper, we assess the reliability of the error models that are in input and in output of a specific CO2 atmospheric inversion system when it assimilates surface air sample measurements. We confront these error models with the mismatch between 4D simulations of CO 2 and independent satellite retrievals of the total CO2 column. Taking all sources of uncertainties into account, it is shown that both prior and posterior errors are consistent with the actual departures, to the point that the theoretical error reduction brought by the surface measurements on the simulation of the Greenhouse gases Observing SATellite (GOSAT) total column measurements (15%) corresponds to the actual reduction seen over the midlatitude and tropical lands and over the tropical oceans. Key Points Prior and posterior errors are consistent with the departures to GOSAT Biases in GOSAT retrievals should be kept within 0.2 ppm for flux inversion Inversion from surface concentrations fits GOSAT well within GOSAT errors. ©2013 American Geophysical Union. All Rights Reserved. Source


Grinbaum A.,CEA Saclay Nuclear Research Center
Foundations of Physics | Year: 2012

Fine-tuning arguments are a frequent find in the literature on quantum field theory. They are based on naturalness-an aesthetic criterion that was given a precise definition in the debates on the Higgs mechanism. We follow the history of such definitions and of their application at the scale of electroweak symmetry breaking. They give rise to a special interpretation of probability, which we call Gedankenfrequency. Finally, we show that the argument from naturalness has been extended to comparing different models of the physics beyond the Standard Model and that naturalness in this case can at best be understood a socio-historic heuristic. © 2012 Springer Science+Business Media, LLC. Source


Vincent L.,CEA Saclay Nuclear Research Center | Le Roux J.-C.,Electricite de France | Taheri S.,Electricite de France
International Journal of Fatigue | Year: 2012

An extensive study of the uniaxial cyclic material behavior of an AISI 304L austenitic stainless steel is proposed in the high cycle regime and in constant amplitude loadings. More particularly, the effect on the material behavior and lifetime of a mean axial stress is evaluated imposing either a stress or a strain amplitude. Almost no effect is observed on the stress fatigue curve while a reduction of about 30% is obtained on the strain fatigue curve in the endurance regime. It appears that a stress amplitude fatigue parameter or a Smith-Watson-Topper parameter predict accurately such differences based on the material behavior at maximum cyclic softening. © 2011 Elsevier Ltd. All rights reserved. Source


Bouvier A.-S.,University of Lorraine | Deloule E.,University of Lorraine | Metrich N.,CEA Saclay Nuclear Research Center
Journal of Petrology | Year: 2010

St.Vincent and Grenada, known for the presence of high Mg-basalts, are two of the southernmost islands of the Lesser Antilles arc, located at the boundary between the Atlantic and Caribbean Plates. We report here secondary ionization mass spectrometry measurements of trace elements (V, Sr,Y, Zr, Nb, Ba, La to Eu) in basaltic melt inclusions trapped in olivine (Fo90-86) within high-MgO basalts. Combined with previous data on light elements and stable isotopes obtained on the same sample set, these results allow us to decipher the nature of the slab-derived fluids that modified the mantle wedge beneath these two islands.The melt inclusions exhibit trace element patterns that encompass those of the whole-rocks, but with a larger range of variability at Grenada. On the whole, such patterns are trace element enriched but not very fractionated compared with mid-ocean ridge basalt and display typical Ba and Sr enrichment. The variations of mobile/immobile element ratios (e.g. K/La, Sr/Υ) are poorly reconciled with crustal contamination processes but rather track the involvement of early aqueous fluids, which are also responsible for significant increases in Cl/F, B and Cl recorded by the melt inclusions.The variations of immobile element ratios such as La/Sm and Nb/Υ cannot be accounted for by variable extents of melting alone, but also imply the influence of a hydrous sediment-derived melt for St.Vincent, whereas the by far larger enrichments of La and Nb in the Grenada samples require contributions of solute-rich fluids extracted at high temperature and pressure from both subducted oceanic crust and sediments. Moreover, a few Grenada melt inclusions display unusual Zr enrichment (up to 1274ppm), a rare feature in basaltic melts that possibly involves the localized dissolution of zircon.The comparison of trace element distribution patterns in the melt inclusions (MI) and whole-rocks indicates the primary composition of the MI and the interaction of the melt with mantle paragenesis after their entrapment in olivine. © The Author 2010. Published by Oxford University Press. All rights reserved. Source


Retinskaya E.,CEA Saclay Nuclear Research Center | Luzum M.,French National Center for Scientific Research | Ollitrault J.-Y.,French National Center for Scientific Research
Physical Review Letters | Year: 2012

We analyze published data from the ALICE Collaboration in order to obtain the first extraction of the recently proposed rapidity-even directed flow observable v 1. An accounting of the correlation due to the conservation of transverse momentum restores the factorization seen by ALICE in all other Fourier harmonics and thus indicates that the remaining correlation gives a reliable measurement of directed flow. We then carry out the first viscous hydrodynamic calculation of directed flow, and show that it is less sensitive to viscosity than higher harmonics. This allows for a direct extraction of the dipole asymmetry of the initial state, providing a strict constraint on the nonequilibrium dynamics of the early-time system. A prediction is then made for v 1 in Au-Au collisions at RHIC. © 2012 American Physical Society. Source


Jamelot E.,CEA Saclay Nuclear Research Center | Ciarlet P.,ENSTA ParisTech
Journal of Computational Physics | Year: 2013

Studying numerically the steady state of a nuclear core reactor is expensive, in terms of memory storage and computational time. In order to address both requirements, one can use a domain decomposition method, implemented on a parallel computer. We present here such a method for the mixed neutron diffusion equations, discretized with Raviart-Thomas-Nédélec finite elements. This method is based on the Schwarz iterative algorithm with Robin interface conditions to handle communications. We analyse this method from the continuous point of view to the discrete point of view, and we give some numerical results in a realistic highly heterogeneous 3D configuration. Computations are carried out with the MINOS solver of the APOLLO3®. 1APOLLO3 is a registered trademark in France.1 neutronics code. © 2013 Elsevier Inc. Source


Bruneval F.,CEA Saclay Nuclear Research Center | Marques M.A.L.,University of Lyon | Marques M.A.L.,CNRS Physics Laboratory of Condensed Matter and Nanostructure
Journal of Chemical Theory and Computation | Year: 2013

The GW approximation is nowadays being used to obtain accurate quasiparticle energies of atoms and molecules. In practice, the GW approximation is generally evaluated perturbatively, based on a prior self-consistent calculation within a simpler approximation. The final result thus depends on the choice of the self-consistent mean-field chosen as a starting point. Using a recently developed GW code based on Gaussian basis functions, we benchmark a wide range of starting points for perturbative GW, including Hartree-Fock, LDA, PBE, PBE0, B3LYP, HSE06, BH&HLYP, CAM-B3LYP, and tuned CAM-B3LYP. In the evaluation of the ionization energy, the hybrid functionals are clearly superior results starting points when compared to Hartree-Fock, to LDA, or to the semilocal approximations. Furthermore, among the hybrid functionals, the ones with the highest proportion of exact-exchange usually perform best. Finally, the reliability of the frozen-core approximation, that allows for a considerable speed-up of the calculations, is demonstrated. © 2012 American Chemical Society. Source


Nicosia V.,Queen Mary, University of London | Bianconi G.,Queen Mary, University of London | Latora V.,Queen Mary, University of London | Latora V.,University of Catania | Barthelemy M.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2013

We propose a modeling framework for growing multiplexes where a node can belong to different networks. We define new measures for multiplexes and we identify a number of relevant ingredients for modeling their evolution such as the coupling between the different layers and the distribution of node arrival times. The topology of the multiplex changes significantly in the different cases under consideration, with effects of the arrival time of nodes on the degree distribution, average shortest path length, and interdependence. © 2013 American Physical Society. Source


Rainone C.,Ecole Normale Superieure de Paris | Rainone C.,University of Rome La Sapienza | Urbani P.,CEA Saclay Nuclear Research Center | Yoshino H.,Osaka University | Zamponi F.,Ecole Normale Superieure de Paris
Physical Review Letters | Year: 2015

We consider the adiabatic evolution of glassy states under external perturbations. The formalism we use is very general. Here we use it for infinite-dimensional hard spheres where an exact analysis is possible. We consider perturbations of the boundary, i.e., compression or (volume preserving) shear strain, and we compute the response of glassy states to such perturbations: pressure and shear stress. We find that both quantities overshoot before the glass state becomes unstable at a spinodal point where it melts into a liquid (or yields). We also estimate the yield stress of the glass. Finally, we study the stability of the glass basins towards breaking into sub-basins, corresponding to a Gardner transition. We find that close to the dynamical transition, glasses undergo a Gardner transition after an infinitesimal perturbation. © 2015 American Physical Society. Source


Cirelli M.,CEA Saclay Nuclear Research Center | Serpico P.D.,University of Savoy | Zaharijas G.,Abdus Salam International Center For Theoretical Physics
Journal of Cosmology and Astroparticle Physics | Year: 2013

We discuss the often-neglected role of bremsstrahlung processes on the interstellar gas in computing indirect signatures of Dark Matter (DM) annihilation in the Galaxy, particularly for light DM candidates in the phenomenologically interesting (10) GeV mass range. Especially from directions close to the Galactic Plane, the γ-ray spectrum is altered via two effects: directly, by the photons emitted in the bremsstrahlung process by energetic electrons which are among the DM annihilation byproducts; indirectly, by the modification of the same electron spectrum, due to the additional energy loss process in the diffusion-loss equation (e.g. the resulting inverse Compton emission is altered). We quantify the importance of the bremsstrahlung emission in the GeV energy range, showing that it is sometimes the dominant component of the γ-ray spectrum. We also find that, in regions in which bremsstrahlung dominates energy losses, the related γ-ray emission is only moderately sensitive to possible large variations in the gas density. Still, we stress that, for computing precise spectra in the (sub-)GeV range, it is important to obtain a reliable description of the Galaxy gas distribution as well as to compute self-consistently the γ-ray emission and the solution to the diffusion-loss equation. For example, these are crucial issues to quantify and interpret meaningfully γ-ray map 'residuals' in the inner Galaxy. © 2013 IOP Publishing Ltd and Sissa Medialab srl. Source


Comini P.,CEA Saclay Nuclear Research Center | Hervieux P.-A.,CNRS Institute of Genetics and of Molecular and Cellular Biology
New Journal of Physics | Year: 2013

In the framework of the gravitational behaviour of antihydrogen at rest (GBAR) experiment, cross sections for the successive formation of H+ and H-+ from collisions between positronium (Ps) and antiprotons ( p ) have been computed in the range 030 keV -P energy, using the continuum distorted wavefinal state theoretical model in its three-body and four-body formulations. The effect of the electronic correlations in H -+ on the total cross sections of H-+ production has been studied using three different wave functions for H? (the matter equivalent of H-+). Ps excited states up to np = 3, as well as H- excited states up to nh = 4, have been investigated. The results suggest that the production of H-+ can be efficiently enhanced by using either a fraction of Ps(2p) and a 2 keV (-P) beam or a fraction Ps(3d) and antiprotons with kinetic energy below 1 keV. Source


Erickcek A.L.,University of Toronto | Erickcek A.L.,Perimeter Institute for Theoretical Physics | Barnaby N.,University of Cambridge | Burrage C.,University of Nottingham | Huang Z.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2013

The physics of the "dark energy" that drives the current cosmological acceleration remains mysterious, and the dark sector may involve new light dynamical fields. If these light scalars couple to matter, a screening mechanism must prevent them from mediating an unacceptably strong fifth force locally. Here we consider a concrete example: the chameleon mechanism. We show that the same coupling between the chameleon field and matter employed by the screening mechanism also has catastrophic consequences for the chameleon during the Universe's first minutes. The chameleon couples to the trace of the stress-energy tensor, which is temporarily nonzero in a radiation-dominated universe whenever a particle species becomes nonrelativistic. These "kicks" impart a significant velocity to the chameleon field, causing its effective mass to vary nonadiabatically and resulting in the copious production of quantum fluctuations. Dissipative effects strongly modify the background evolution of the chameleon field, invalidating all previous classical treatments of chameleon cosmology. Moreover, the resulting fluctuations have extremely high characteristic energies, which casts serious doubt on the validity of the effective theory. Our results demonstrate that quantum particle production can profoundly affect scalar-tensor gravity, a possibility not previously considered. Working in this new context, we also develop the theory and numerics of particle production in the regime of strong dissipation. © 2013 American Physical Society. Source


Semerok A.,CEA Saclay Nuclear Research Center | Grisolia C.,French Atomic Energy Commission
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

Feasibility of in situ LIBS remote measurements with the plasma facing components (PFCs) from the European tokamaks (TORE SUPRA, CEA Cadarache, France and TEXTOR, Julich, Germany) has been studied in laboratory using Q-switched nanosecond Nd-YAG lasers. LIBS particular properties and optimal parameters were determined for in-depth PFCs characterisation. The LIBS method was in situ tested on the Joint European Torus (JET) in the UK with the EDGE LIDAR Laser System (Ruby laser, 3 J, 690 nm wavelength, 300 ps pulse duration, intensity up to 70 GW/cm2). Several analytical spectral lines of H, CII, CrI, and BeII in plasma were observed and identified in 400-600 nm spectral range with the optimised LIBS and detection system. The LIBS in-depth cartography is in agreement with the surface properties of the tile under analysis, thus confirming feasibility of in situ LIBS. Further LIBS technique improvements required to provide tritium concentration measurements more accurately are discussed. © 2012 Elsevier B.V. All rights reserved. Source


Kim J.,Ohio State University | Roblin P.,Ohio State University | Chaillot D.,CEA Saclay Nuclear Research Center | Xie Z.,University of North Carolina at Greensboro
IEEE Transactions on Microwave Theory and Techniques | Year: 2013

This paper presents a new architecture for the frequency-selective digital predistortion (DPD) for two-and three-band power amplifier (PA) linearization. Also, largely spaced-signal DPD using a digital intermediate frequency (IF) technique is demonstrated. The algorithm used accounts for differential memory effects up to fifth order for bands that can be arbitrarily spaced. The simulation and experimental studies are performed using various signal sets; two-and three-band multitone signals with various tone spacing, band separation, and complementary cumulative distribution function. An improvement of 10 dB over third-order linearization is demonstrated in simulation for more than 20 dB of adjacent channel power ratio reduction. The test signal and the linearization algorithm were implemented on a field-programmable gate array. The linearization algorithm was applied to an RF amplifier at 700-900 MHz. For the two-band case, more than 15 dB on the in-band, 13 dB on the third, and 5 dB on the fifth intermodulation distortion (IMD) cancellation were achieved. For the three-band case, more than 12 dB of IMD cancellation was observed. For largely spaced signal DPD, more than 15 dB of IMD cancellation was achieved. In the three-band case, the linearization of intermodulation byproducts overlapping with the in-band distortion is found to be of critical importance. © 1963-2012 IEEE. Source


El-Showk S.,CEA Saclay Nuclear Research Center | Paulos M.F.,Brown University
Physical Review Letters | Year: 2013

The existence of a positive linear functional acting on the space of (differences between) conformal blocks has been shown to rule out regions in the parameter space of conformal field theories (CFTs). We argue that at the boundary of the allowed region the extremal functional contains, in principle, enough information to determine the dimensions and operator product expansion (OPE) coefficients of an infinite number of operators appearing in the correlator under analysis. Based on this idea we develop the extremal functional method (EFM), a numerical procedure for deriving the spectrum and OPE coefficients of CFTs lying on the boundary (of solution space). We test the EFM by using it to rederive the low lying spectrum and OPE coefficients of the two-dimensional Ising model based solely on the dimension of a single scalar quasiprimary - no Virasoro algebra required. Our work serves as a benchmark for applications to more interesting, less known CFTs in the near future. © 2013 American Physical Society. Source


Mukhopadhyay A.,Ecole Polytechnique - Palaiseau | Mukhopadhyay A.,CEA Saclay Nuclear Research Center | Policastro G.,Ecole Normale Superieure de Paris
Physical Review Letters | Year: 2013

We analyze some phenomenological implications of the most general semiholographic models for non-Fermi liquids that have emerged with inputs from the holographic correspondence. We find generalizations of Landau-Silin equations with few parameters governing thermodynamics, low-energy response, and collective excitations. We show that even when there is a Fermi surface with well-defined quasiparticle excitations, the collective excitations can behave very differently from Landau's theory. © 2013 American Physical Society. Source


Brax P.,CEA Saclay Nuclear Research Center | Burrage C.,University of Geneva | Davis A.-C.,University of Cambridge
Journal of Cosmology and Astroparticle Physics | Year: 2011

The Galileon model is a ghost free scalar effective field theory containing higher derivative terms that are protected by the Galileon symmetry. The presence of a Vainshtein screening mechanism allows the scalar field to couple to matter without mediating unacceptably large fifth forces in the solar system. We describe how laboratory measurements of the Casimir effect and possible deviations from Newtonian gravity can be used to search for Galileon scalar fields. Current experimental measurements are used to bound a previously unconstrained combination of Galileon parameters. © 2011 IOP Publishing Ltd and SISSA. Source


Cirelli M.,CEA Saclay Nuclear Research Center | Del Nobile E.,University of Southern Denmark | Del Nobile E.,University of California at Los Angeles | Panci P.,University of Southern Denmark
Journal of Cosmology and Astroparticle Physics | Year: 2013

We discuss a framework (based on non-relativistic operators) and a self-contained set of numerical tools to derive the bounds from some current direct detection experiments on virtually any arbitrary model of Dark Matter elastically scattering on nuclei. © 2013 IOP Publishing Ltd and Sissa Medialab srl. Source


Brax P.,CEA Saclay Nuclear Research Center | Burrage C.,University of Nottingham | Davis A.-C.,University of Cambridge
Journal of Cosmology and Astroparticle Physics | Year: 2013

New fifth forces have not yet been detected in the laboratory or in the solar system, hence it is typically difficult to introduce new light scalar fields that would mediate such forces. In recent years it has been shown that a number of non-linear scalar field theories allow for a dynamical mechanism, such as the Vainshtein and chameleon ones, that suppresses the strength of the scalar fifth force in experimental environments. This is known as screening, however it is unclear how common screening is within non-linear scalar field theories. k-essence models are commonly studied examples of non-linear models, with DBI as the best motivated example, and so we ask whether these non-linearities are able to screen a scalar fifth force. We find that a Vainshtein-like screening mechanism exists for such models although with limited applicability. For instance, we cannot find a screening mechanism for DBI models. On the other hand, we construct a large class of k-essence models which lead to the acceleration of the Universe in the recent past for which the fifth force mediated by the scalar can be screened. © 2013 IOP Publishing Ltd and Sissa Medialab srl. Source


Servant G.,CERN | Servant G.,Autonomous University of Barcelona | Servant G.,CEA Saclay Nuclear Research Center | Tulin S.,University of Michigan
Physical Review Letters | Year: 2013

In addition to explaining the masses of elementary particles, the Higgs boson may have far-reaching implications for the generation of the matter content in the Universe. For instance, the Higgs boson plays a key role in two main theories of baryogenesis, namely, electroweak baryogenesis and leptogenesis. In this Letter, we propose a new cosmological scenario where the Higgs chemical potential mediates asymmetries between visible and dark matter sectors, either generating a baryon asymmetry from a dark matter asymmetry or vice versa. We illustrate this mechanism with a simple model with two new fermions coupled to the Higgs boson and discuss the associated signatures. © 2013 American Physical Society. Source


Zhang L.,ETH Zurich | Petit T.,ETH Zurich | Petit T.,CEA Saclay Nuclear Research Center | Peyer K.E.,ETH Zurich | Nelson B.J.,ETH Zurich
Nanomedicine: Nanotechnology, Biology, and Medicine | Year: 2012

This paper reports an approach to perform basic noncontact and contact manipulation tasks using rotating nickel nanowires driven by a rotating magnetic field. A rotating nanowire is capable of propulsion and steering near a solid surface by a tumbling motion. The FEM simulation shows that fluid flow is induced around the rotating nanowire, which was applied to manipulate micro-objects in a noncontact fashion. Pushing, pulling, and rotation tests of individual polystyrene microbeads are conducted on a solid surface. In addition, targeted delivery tasks of biological samples, e.g., individual flagellated microorganisms and human blood cells, are demonstrated. The results imply that rotating magnetic nanowires are good tools for handling cellular and subcellular objects in an aqueous low-Reynolds-number environment and have potential for single-cell analysis. From the Clinical Editor: In this study, the authors report the ability to push, pull, and rotate individual polystyrene microbeads on a solid surface. Furthermore, they demonstrate targeted delivery of biological samples, implying that rotating magnetic nanowires are good tools for handling cellular and subcellular objects. © 2012 Elsevier Inc. Source


Jentschura U.D.,Missouri University of Science and Technology | Zinn-Justin J.,CEA Saclay Nuclear Research Center
Annals of Physics | Year: 2011

This is the fourth paper in a series devoted to the large-order properties of anharmonic oscillators. We attempt to draw a connection of anharmonic oscillators to field theory, by investigating the partition function in the path integral representation around both the Gaussian saddle point, which determines the perturbative expansion of the eigenvalues, as well as the nontrivial instanton saddle point. The value of the classical action at the saddle point is the instanton action which determines the large-order properties of perturbation theory by a dispersion relation. In order to treat the perturbations about the instanton, one has to take into account the continuous symmetries broken by the instanton solution because they lead to zero-modes of the fluctuation operator of the instanton configuration. The problem is solved by changing variables in the path integral, taking the instanton parameters as integration variables (collective coordinates). The functional determinant (Faddeev-Popov determinant) of the change of variables implies nontrivial modifications of the one-loop and higher-loop corrections about the instanton configuration. These are evaluated and compared to exact WKB calculations. A specific cancellation mechanism for the first perturbation about the instanton, which has been conjectured for the sextic oscillator based on a nonperturbative generalized Bohr-Sommerfeld quantization condition, is verified by an analytic Feynman diagram calculation. © 2011 Elsevier Inc. Source


Haessler S.,Vienna University of Technology | Caillat J.,University Pierre and Marie Curie | Salieres P.,CEA Saclay Nuclear Research Center
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2011

This tutorial presents the most important aspects of the molecular self-probing paradigm, which views the process of high harmonic generation as 'a molecule being probed by one of its own electrons'. Since the properties of the electron wavepacket acting as a probe allow a combination of attosecond and ngström resolutions in measurements, this idea bears great potential for the observation, and possibly control, of ultrafast quantum dynamics in molecules at the electronic level. Theoretical as well as experimental methods and concepts at the basis of self-probing measurements are introduced. Many of these are discussed as the example of molecular orbital tomography. © 2011 IOP Publishing Ltd. Source


Mananga E.S.,Harvard University | Charpentier T.,CEA Saclay Nuclear Research Center
Physics Reports | Year: 2016

Theoretical approaches are useful and powerful tools for more accurate and efficient spin dynamics simulation to understand experiments and devising new RF pulse sequence in nuclear magnetic resonance. Solid-state NMR is definitely a timely topic or area of research, and not many papers on the respective theories are available in the literature of nuclear magnetic resonance or physics reports. This report presents the power and the salient features of the promising theoretical approach called Floquet-Magnus expansion that is helpful to describe the time evolution of the spin system at all times in nuclear magnetic resonance. The report presents a broad view of algorithms of spin dynamics, based on promising and useful theory of Floquet-Magnus expansion. This theory provides procedures to control and describe the spin dynamics in solid-state NMR. Major applications of the Floquet-Magnus expansion are illustrated by simple solid-state NMR and physical applications such as in nuclear, atomic, molecular physics, and quantum mechanics, NMR, quantum field theory and high energy physics, electromagnetism, optics, general relativity, search of periodic orbits, and geometric control of mechanical systems. The aim of this report is to bring to the attention of the spin dynamics community, the bridge that exists between solid-state NMR and other related fields of physics and applied mathematics. This review article also discusses future potential theoretical directions in solid-state NMR. © 2015 Elsevier B.V. Source


Boulant N.,CEA Saclay Nuclear Research Center | Hoult D.I.,National Research Council Canada
Magnetic Resonance in Medicine | Year: 2012

When designing a radio-frequency pulse to produce a desired dependence of magnetization on frequency or position, the small flip angle approximation is often used as a first step, and a Fourier relation between pulse and transverse magnetization is then invoked. However, common intuition often leads to linear scaling of the resulting pulse so as to produce a larger flip angle than the approximation warrants-with surprisingly good results. Starting from a modified version of the Bloch-Riccati equation, a differential equation in the flip angle itself, rather than in magnetization, is derived. As this equation has a substantial linear component that is an instance of Fourier's equation, the intuitive approach is seen to be justified. Examples of the accuracy of this higher tip angle approximation are given for both constant- and variable-phase pulses. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc. Source


Zhang J.-H.,CEA Saclay Nuclear Research Center
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

A duality relation has been proposed between the planar gluon MHV amplitudes and light-like Wilson loops in N=4 super Yang-Mills. At six-point two-loop, the results for the planar gluon MHV amplitude and for the light-like Wilson loop agree, but they both differ from the Bern-Dixon-Smirnov ansatz by a finite remainder function. Recently Del Duca, Duhr and Smirnov presented an analytical result for the two-loop hexagon Wilson loop remainder function in general kinematics. Their result is rather lengthy, and the dependence on the conformal cross ratios appears in a complicated way. Here we present an alternate, more compact representation for the two-loop hexagon Wilson loop remainder function. © 2011 Elsevier B.V. Source


Petit S.,CEA Saclay Nuclear Research Center
Nature Physics | Year: 2016

Fractionalized excitations that emerge from a many-body system have revealed rich physics and concepts, from composite fermions in two-dimensional electron systems, revealed through the fractional quantum Hall effect, to spinons in antiferromagnetic chains and, more recently, fractionalization of Dirac electrons in graphene and magnetic monopoles in spin ice. Even more surprising is the fragmentation of the degrees of freedom themselves, leading to coexisting and a priori independent ground states. This puzzling phenomenon was recently put forward in the context of spin ice, in which the magnetic moment field can fragment, resulting in a dual ground state consisting of a fluctuating spin liquid, a so-called Coulomb phase, on top of a magnetic monopole crystal. Here we show, by means of neutron scattering measurements, that such fragmentation occurs in the spin ice candidate Nd2Zr2O7. We observe the spectacular coexistence of an antiferromagnetic order induced by the monopole crystallization and a fluctuating state with ferromagnetic correlations. Experimentally, this fragmentation manifests itself through the superposition of magnetic Bragg peaks, characteristic of the ordered phase, and a pinch point pattern, characteristic of the Coulomb phase. These results highlight the relevance of the fragmentation concept to describe the physics of systems that are simultaneously ordered and fluctuating. © 2016 Nature Publishing Group Source


Holt J.W.,University of Washington | Rho M.,Hanyang University | Rho M.,CEA Saclay Nuclear Research Center | Weise W.,TU Munich
Physics Reports | Year: 2016

Chiral symmetry, first entering in nuclear physics in the 1970s for which Gerry Brown played a seminal role, has led to a stunningly successful framework for describing strongly-correlated nuclear dynamics both in finite and infinite systems. We review how the early, germinal idea conceived with the soft-pion theorems in the pre-QCD era has evolved into a highly predictive theoretical framework for nuclear physics, aptly assessed by Steven Weinberg: "it (chiral effective field theory) allows one to show in a fairly convincing way that what they (nuclear physicists) have been doing all along... is the correct first step in a consistent approximation scheme". Our review recounts both how the theory presently fares in confronting Nature and how one can understand its extremely intricate workings in terms of the multifaceted aspects of chiral symmetry, namely, chiral perturbation theory, skyrmions, Landau Fermi-liquid theory, the Cheshire cat phenomenon, and hidden local and mended symmetries. © 2015 Elsevier B.V. Source


Bialas A.,Polish Academy of Sciences | Bialas A.,Jagiellonian University | Peschanski R.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2011

The possibility that particle production in high-energy collisions is a result of two asymmetric hydrodynamic flows is investigated using the Khalatnikov form of the (1+1)-dimensional approximation of hydrodynamic equations. The general solution is discussed and applied to the physically appealing "generalized in-out cascade" where the space-time and energy-momentum rapidities are equal at initial temperature but boost invariance is not imposed. It is demonstrated that the two-bump structure of the entropy density, characteristic of the asymmetric input, changes easily into a single broad maximum compatible with data on particle production in symmetric processes. A possible microscopic QCD interpretation of asymmetric hydrodynamics is proposed. © 2011 American Physical Society. Source


Gelis F.,CEA Saclay Nuclear Research Center | Tanji N.,University of Heidelberg
Progress in Particle and Nuclear Physics | Year: 2016

In this article, we review recent theoretical works on the Schwinger mechanism of particle production in external electrical fields. Although the non-perturbative Schwinger mechanism is at the center of this discussion, many of the approaches that we discuss can cope with general time and space dependent fields, and therefore also capture the perturbative contributions to particle production. © 2015 Elsevier B.V. All rights reserved. Source


El-Showk S.,CEA Saclay Nuclear Research Center | Nakayama Y.,California Institute of Technology | Rychkov S.,University Pierre and Marie Curie
Nuclear Physics B | Year: 2011

The free Maxwell theory in d≠4 dimensions provides a physical example of a unitary, scale invariant theory which is NOT conformally invariant. The easiest way to see this is that the field strength operator Fμν is neither a primary nor a descendant. We show how conformal multiplets can be completed, and conformality restored, by adding new local operators to the theory. In d≥5, this can only be done by sacrificing unitarity of the extended Hilbert space. We analyze the full symmetry structure of the extended theory, which turns out to be related to the OSp(d,2|2) superalgebra. © 2011 Elsevier B.V. Source


Aldazabal G.,Bariloche Atomic Center | Marques D.,CEA Saclay Nuclear Research Center | Nunez C.,University of Buenos Aires | Rosabal J.A.,Bariloche Atomic Center
Nuclear Physics B | Year: 2011

We analyze D=4 compactifications of Type IIB theory with generic, geometric and non-geometric, dual fluxes turned on. In particular, we study N=1 toroidal orbifold compactifications that admit an embedding of the untwisted sector into gauged N=4,8 supergravities. Truncations, spontaneous breaking of supersymmetry and the inclusion of sources are discussed. The algebraic identities satisfied by the supergravity gaugings are used to implement the full set of consistency constraints on the background fluxes. This allows to perform a generic study of N=1 vacua and identify large regions of the parameter space that do not admit complete moduli stabilization. Illustrative examples of AdS and Minkowski vacua are presented. © 2011 Elsevier B.V. Source


Zaehle S.,Max Planck Institute for Biogeochemistry | Ciais P.,CEA Saclay Nuclear Research Center | Friend A.D.,University of Cambridge | Prieur V.,Max Planck Institute for Biogeochemistry
Nature Geoscience | Year: 2011

Additions of reactive nitrogen to terrestrial ecosystemsg-primarily through fertilizer application and atmospheric depositiong-have more than doubled since 1860 owing to human activities. Nitrogen additions tend to increase the net uptake of carbon by the terrestrial biosphere, but they also stimulate nitrous oxide release from soils. However, given that the magnitude of these effects is uncertain, and that the carbon and nitrogen cycles are tightly coupled, the net climatic impact of anthropogenic nitrogen inputs is unknown. Here we use a process-based model of the terrestrial biosphere to evaluate the overall impact of anthropogenic nitrogen inputs on terrestrial ecosystem carbon and nitrous oxide fluxes between 1700 and 2005. We show that anthropogenic nitrogen inputs account for about a fifth of the carbon sequestered by terrestrial ecosystems between 1996 and 2005, and for most of the increase in global nitrous oxide emissions in recent decades; the latter is largely due to agricultural intensification. We estimate that carbon sequestration due to nitrogen deposition has reduced current carbon dioxide radiative forcing by 96± 14mWm-2. However, this effect has been offset by the increase in radiative forcing resulting from nitrous oxide emissions, which amounts to 125± 20mWm2. © 2011 Macmillan Publishers Limited. All rights reserved. Source


Kirilovsky D.,CEA Saclay Nuclear Research Center
Advances in experimental medicine and biology | Year: 2010

Photoprotective mechanisms have been evolved by photosynthetic organisms to cope with fluctuating high light conditions. One of these mechanisms downregulates photosynthesis by increasing thermal dissipation of the energy absorbed by the photosystem II antenna. While this process has been well studied in plants, the equivalent process in cyanobacteria was only recently discovered. In this chapter we describe the results leading to its discovery and the more recent advances in the elucidation of this mechanism. The light activation of a soluble carotenoid protein, the orange carotenoid protein (OCP), binding hydroxyechinenone, is the key inducer of this photoprotective mechanism. Light causes structural changes within both the carotenoid and the protein, leading to the conversion of an orange inactive form into a red active form. The activated red form induces an increase of energy dissipation leading to a decrease in the fluorescence of the phycobilisomes, the cyanobacterial antenna, and thus of the energy arriving to the reaction centers. The OCP, which senses light and triggers photoprotection, is a unique example of a photoactive protein containing a carotenoid as the photoresponsive chromophore. Source


Chiappetta G.,CEA Saclay Nuclear Research Center
Methods in enzymology | Year: 2010

The oxidation of the cysteine (Cys) residue to sulfenic (-S-OH), disulfide (-S-S-), or S-nitroso (S-NO) forms are thought to be a posttranslational modifications that regulate protein function. However, despite a few solid examples of its occurrence, thiol-redox regulation of protein function is still debated and often seen as an exotic phenomenon. A systematic and exhaustive characterization of all oxidized Cys residues, an experimental approach called redox proteomics or redoxome analysis, should help establish the physiological scope of Cys residue oxidation and give clues to its mechanisms. Redox proteomics still remains a technical challenge, mainly because of the labile nature of thiol-redox reactions and the lack of tools to directly detect the modified residues. Here we consider recent technical advances in redox proteomics, focusing on a gel-based fluorescent method and on the shotgun OxICAT technique. Copyright (c) 2010 Elsevier Inc. All rights reserved. Source


Godat E.,CEA Saclay Nuclear Research Center
Methods in enzymology | Year: 2010

The sulfur metabolic pathway plays a central role in cell metabolism. It provides the sulfur amino acids methionine and cysteine, which are essential for protein synthesis, homocysteine, which lies at a critical juncture of this pathway, S-adenosylmethionine, the universal methyl donor in the cell, and glutathione (GSH), which has many crucial functions including protection against oxidative stress and xenobiotics. The intracellular level of these metabolites, which are closely connected with other cellular metabolic pathways, is of major importance for cell physiology and health. Three mass spectrometry-based methods for the determination of sulfur metabolites and also related compounds linked to the glutathione biosynthesis pathway are presented and discussed. The first one enables absolute quantification of these metabolites in cell extracts. It is based on liquid chromatography-electrospray triple quadrupole mass spectrometry coupled to (15)N uniform metabolic labeling of the yeast Saccharomyces cerevisiae. The two other methods are global approaches to metabolite detection involving a high-resolution mass spectrometer, the LTQ-Orbitrap. Ions related to metabolites of interest are picked up from complex and information-rich metabolic fingerprints. By these means, it is possible to detect analytical information outside the initial scope of investigation. Copyright (c) 2010 Elsevier Inc. All rights reserved. Source


Pedone A.,University of Modena and Reggio Emilia | Charpentier T.,CEA Saclay Nuclear Research Center | Menziani M.C.,University of Modena and Reggio Emilia
Journal of Materials Chemistry | Year: 2012

Fluoride-containing bioactive glasses are attracting particular interest in many fields of dentistry and orthopedics because they combine the bone-bonding ability of bioactive glasses with the anticariogenic protection provided by fluoride ions. Since the biomedical applications of these materials critically depend on the release of ionic species in the surrounding physiological environment, a deep knowledge of their environments is required. In this paper, density functional theory calculations and spin effective Hamiltonians have been employed to analyse the NMR signatures of the various environments of 19F, 29Si, 31P and 23Na atoms in fluorinated bioglasses structural models previously generated by Car-Parrinello molecular dynamics simulations. Comparison with experimental spectra expressly recorded in this work shows a good agreement and allows the enlightenment of some longstanding issues about the atomic structure of fluorinated bioglasses, such as the presence of Si-F and Si-O-P bonds. In particular, it is shown that Si-F bonds cannot be resolved by using MAS NMR experiments only, and 29Si{ 19F} REDOR experiments, that probes directly spatial proximities among atoms, must be employed. Our results show that F is coordinated entirely to the modifier ions Na and Ca, and that no Si-F bonds are present in the real glass structure. Thus, the addition of fluorine to the 45S5 Bioglass® increases the polymerization of the silicate network by removing modifiers from the siliceous matrix and reducing its reactivity. Finally, the computed isotropic chemical shifts of the various environments of phosphorus show that, if present, Si-O-P bonds should be clearly noticeable in the 31P static NMR experimental spectrum. Instead, the latter show that P is present as isolated orthophosphate units and does not enter into the siliceous matrix by forming Si-O-P bonds as conjectured by molecular dynamics simulations. © 2012 The Royal Society of Chemistry. Source


Thuery P.,CEA Saclay Nuclear Research Center
Inorganic Chemistry | Year: 2011

The crystal structures of the complexes formed by reaction of thorium(IV) nitrate with iminodiacetic acid (H2IDA), nitrilotriacetic acid (H3NTA), and ethylenediaminetetraacetic acid (H4EDTA) under hydrothermal conditions are reported. In [Th(HIDA)2(C 2O4)]•H2O (1), the metal atom is chelated by two carboxylate groups from two HIDA- anions and by two oxalate ligands formed in situ; two additional oxygen atoms from two more HIDA - anions complete the ten-coordinate environment of bicapped square antiprismatic geometry. The uncoordinated nitrogen atom is protonated and involved in hydrogen bonding. Two different ligands are present in [Th(NTA)(H2NTA)(H2O)]•H2O (2), one of them being a O3,N-chelating trianion which acts also as a bridge toward two neighboring metal ions, and the other being a bis-monodentate bridging species with an uncoordinated carboxylic arm and a central ammonium group. An aqua ligand completes the nine-coordinated, capped square antiprismatic metal environment. The EDTA4- anion in [Th(EDTA)(H2O)] •2H2O (3) is chelating through one oxygen atom from each carboxylate group and the two nitrogen atoms, as in a previously reported molecular complex. Two carboxylate groups are bridging, which, with the addition of an aqua ligand, gives a capped square antiprismatic coordination polyhedron. Aminopolycarboxylate ligands have been much investigated in relation with actinide decorporation and nuclear wastes management studies, and the present results add to the structural information available on their complexes with thorium(IV), which has mainly been obtained up to now by extended X-ray absorption fine structure (EXAFS) spectroscopy. In particular, the bridging (non-chelating) coordination mode of H2NTA- is a novel feature in this context. All three complexes crystallize as two-dimensional assemblies and are thus novel examples of thorium-organic coordination polymers. © 2011 American Chemical Society. Source


Thuery P.,CEA Saclay Nuclear Research Center
Crystal Growth and Design | Year: 2011

The complexes formed by uranyl nitrate with the three positional isomers of sulfobenzoate and with ethanedisulfonate anions in the presence of cucurbit[6]uril (CB6) under hydrothermal conditions were investigated by single-crystal X-ray diffraction. 2-Sulfobenzoate (2-SB 2-) chelates the uranyl ion through one carboxylate and one sulfonate oxygen atoms in the three complexes [UO 2(2-SB)(H 2O) 3] 2•CB6•12H 2O (1), [Na(CB6)(H 2O) 4][UO 2(2-SB)(H 2O) 2] 2•NO 3•3H 2O (2), and {[UO 2(2-SB)(H 2O) 2] 2Cs(CB6)(OH)(H 2O) 5}•2H 2O (3). While 1 is a monomer, 2 and 3 display neutral dimeric [UO 2(2-SB)(H 2O) 2] 2 units. In 2, these units are bound to the sodium ion complex of CB6 through hydrogen bonds, while, in 3, bonding of one of the uranyl water ligands to cesium gives a one-dimensional coordination polymer. 3-Sulfobenzoate (3-SB 2-) gives the three-dimensional framework [(UO 2) 2Cs 2(3-SB) 3(CB6)(H 2O) 4.5]•7.5H 2O (4), in which carboxylate groups are chelating or bridging uranyl ions, and sulfonate groups are coordinated to uranyl and cesium ions, the latter being also bound to CB6 carbonyl groups. In contrast, the para isomer 4-SB 2- gives the molecular species [UO 2K 2(4-SB) 2(CB6)(H 2O) 9]•11H 2O (5), in which uranyl is bound to one monodentate carboxylate group from each ligand, and one sulfonate oxygen atom is bound to one of the potassium ions complexed by CB6. Ethanedisulfonate (EDS 2-) was chosen as a potentially bridging, homo-difunctional ligand devoid of the strongly uranyl-binding carboxylate groups. The complex [(UO 2) 4(EDS)(OH) 6(CB6)(H 2O) 2]•8H 2O (6) is a three-dimensional framework with a remarkable architecture: uranyl-bridging hydroxides give rise to undulated chains which are linked to one another by bridging, tetradentate disulfonate ligands to give planar two-dimensional subunits displaying large [(UO 2) 8(EDS) 2(OH) 10] rings, and these sheets are assembled into a unique network by uranyl-bound CB6 molecules. Both frameworks 4 and 6 are novel examples of the association of uranyl-organic sheets with CB6 columns or layers, a quite frequent feature in this family of compounds. © 2011 American Chemical Society. Source


Bary B.,CEA Saclay Nuclear Research Center
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2011

This study focuses on the estimation of mechanical, hydromechanical and thermal conduction parameters of isotropic microcracked hydrated cement pastes in unsaturated conditions. The prediction of these parameters is obtained as a function of saturation degree and isotropic microcrack density parameter by applying an explicit effective medium approximation scheme on the basis of a simple microstructure description of the material. This latter is supposed to be composed of a homogeneous matrix in which are distributed ellipsoidal particles and penny-shaped inclusions representing pores and microcracks, respectively. These two types of inclusions are assumed to be of well-separated sizes so that a two-step homogenization procedure is employed. The effects of the pore shape and both open and close microcracks on the considered physical properties are investigated in partially saturated conditions by adopting a simplified desaturation-resaturation scenario. It is shown that the saturation degree repercussions on these properties increase when the pores have an oblate shape with low aspect ratio. Moreover, while Biot coefficient and thermal conductivity are significantly affected by saturation degree, undrained mechanical parameters appear to be only moderately modified by this factor. Besides, as expected microcracks induce important changes in all properties. The effects of the adsorbed water layers covering the surface of desaturated pores on the Biot coefficient are investigated by making use of the disjoining pressure concept, and results show only a moderate influence for very small pores. © 2010 John Wiley & Sons, Ltd. Source


Delluc S.,Proteus | Ravot G.,Proteus | Maillere B.,CEA Saclay Nuclear Research Center
Blood | Year: 2010

Antibody-mediated pure red cell aplasia is a rare but serious event resulting from the induction of neutralizing erythropoietin (Epo)-specific antibodies provoked by treatment with recombinant Epo. Because of the crucial role of CD4 T cells in humoral response, we have quantified the number of Epo-specific CD4 T cells in the blood of normal donors by in vitro stimulation. An important repertoire of preexisting Epo-specific T cells was observed in almost half of the donors, comparable with that of non-self-proteins. This observation suggests that, at the steady state, endogenous Epo weakly contributes to tolerance induction and may be ignored by the immune system. As a result, circulating Epo-specific CD4 T cells could be prone to be activated by altered batches of Epo, providing them with costimulatory signals. Our data also highlight the relevance of T-cell assays performed with normal donors to evaluate the potential immunogenicity of therapeutic proteins. © 2010 by The American Society of Hematology. Source


Casalderrey-Solana J.,CERN | Iancu E.,CERN | Iancu E.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2011

As a step towards understanding the in-medium evolution of a hard jet, we consider the interference pattern for the medium-induced gluon radiation produced by a color singlet quark-antiquark antenna embedded in a QCD medium with size L. We focus on the typical kinematics for medium-induced gluon radiation in the BDMPS-Z regime, that is, short formation times τf L and relatively large emission angles Θ Θl c ≡ 2/√q̂L3, with q̂ the 'jet quenching' parameter. We demonstrate that, for a dipole opening angle Θqq larger than Θc, the interference between the medium-induced gluon emissions by the quark and the antiquark is parametrically suppressed with respect to the corresponding direct emissions. Physically, this is so since the direct emissions can be delocalized anywhere throughout the medium and thus yield contributions proportional to L. On the contrary, the interference occurs only between gluons emitted at very early times, within the characteristic time scales for quantum and color coherence between the two emitters, which in this regime are much smaller than L. This implies that, for Θqq Θc, the medium-induced radiation by the dipole is simply the sum of the two BDMPS-Z spectra individually produced by the quark and the antiquark, without coherence effects like angular ordering. For Θqq Θc, the medium-induced radiation by the dipole vanishes. © SISSA 2011. Source


Brax P.,CEA Saclay Nuclear Research Center | Davis A.-C.,University of Cambridge | Sakstein J.,University of Cambridge
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We present a framework for embedding scalar-tensor models of screened modified gravity such as chameleons, symmetrons and environmental dilatons into global supersymmetry. This achieved by secluding the dark sector from both the observable and supersymmetry breaking sectors. We examine the resulting supersymmetric features in a model-independent manner and find that, when the theory follows from an underlying supergravity, the mediation of supersymmetry breaking to the dark sector induces a soft mass for the scalar of order the gravitino mass. This is enough to forbid the construction of supersymmetric symmetrons and ensures that when other screening mechanisms operate, no object in the Universe is unscreened thereby precluding any observable signatures. In view of a possible origin of modified gravity within fundamental physics, we find that only no-scale models can circumvent these features. We also present a novel mechanism where the coupling of the scalar to two other scalars charged under U(1) can dynamically generate a small cosmological constant at late times in the form of a Fayet-Iliopoulos term. © 2013 Elsevier B.V. Source


Casalderrey-Solana J.,University of Barcelona | Mehtar-Tani Y.,CEA Saclay Nuclear Research Center | Salgado C.A.,University of Santiago de Compostela | Tywoniuk K.,Lund University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We propose a new description of the jet quenching phenomenon observed in nuclear collisions at high energies in which coherent parton branching plays a central role. This picture is based on the appearance of a dynamically generated scale, the jet resolution scale, which controls the transverse resolution power of the medium to simultaneously propagating color probes. Since from the point of view of the medium all partonic jet fragments within this transverse distance act coherently as a single emitter, this scale allows us to rearrange the jet shower into effective emitters. We observe that in the kinematic regime of the LHC, the corresponding characteristic angle is comparable to the typical opening angle of high-energy jets such that most of the jet energy is contained within a non-resolvable color coherent inner core. Thus, a sizable fraction of the jets is unresolved, losing energy as a single parton without modifications of their intra-jet structure. © 2013 Elsevier B.V. Source


Ferreiro E.G.,University of Santiago de Compostela | Fleuret F.,Ecole Polytechnique - Palaiseau | Lansberg J.P.,University Paris - Sud | Rakotozafindrabe A.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2013

Based on our previous studies, we predict the nuclear-matter effects on J/ψ production in proton-nucleus collisions for the recent Large Hadron Collider pPb runs at √sNN=5 TeV. We have analyzed the effects of the modification of the gluon parton distribution functions in the nucleus, using an exact kinematics for a 2→2 process, namely, g+g→J/ψ+g as expected from leading-order perturbative QCD. This allows us to constrain the transverse-momentum while computing the nuclear modification factor for different rapidities, unlike with the usual simplified kinematics. Owing to the absence of measurement in pp collisions at the same √sNN and owing to the expected significant uncertainties in yield interpolations which would hinder definite interpretations of the nuclear modification factor R pPb, we have derived forward-to-backward and central-to-peripheral yield ratios in which the unknown proton-proton yield cancels. These have been computed without and with a transverse-momentum cut, e.g., to comply with the ATLAS and CMS constraints in the central-rapidity region. © 2013 American Physical Society. Source


Piazza F.,University Paris Diderot | Piazza F.,Paris West University Nanterre La Defense | Vernizzi F.,CEA Saclay Nuclear Research Center | Vernizzi F.,French National Center for Scientific Research
Classical and Quantum Gravity | Year: 2013

The effective field theory of cosmological perturbations stems from considering a cosmological background solution as a state displaying spontaneous breaking of time translations and (adiabatic) perturbations as the related Nambu-Goldstone modes. With this insight, one can systematically develop a theory for the cosmological perturbations during inflation and, with minor modifications, also describe in full generality the gravitational interactions of dark energy, which are relevant for late-time cosmology. The formalism displays a unique set of Lagrangian operators containing an increasing number of cosmological perturbations and derivatives. We give an introductory description of the unitary gauge formalism for theories with broken gauge symmetry - that allows us to write down the most general Lagrangian - and of the Stückelberg 'trick' - that allows to recover gauge invariance and to make the scalar field explicit. We show how to apply this formalism to gravity and cosmology and we reproduce the detailed analysis of the action in the ADM variables. We also review some basic applications to inflation and dark energy. © 2013 IOP Publishing Ltd. Source


Brax P.,CEA Saclay Nuclear Research Center
Classical and Quantum Gravity | Year: 2013

The ubiquitous role of light scalar fields in modified gravity models necessitates the introduction of screening mechanisms whereby gravitation in the solar system can be described by the General Theory of Relativity to an extremely precise level. On larger scales, the laws of gravity can be modified with various phenomelogical consequences. We review the status of the three main mechanisms when a single scalar field modifies gravity. We emphasize the qualitative and quantitative differences between the models subject to the chameleon and the Damour-Polyakov mechanisms on the one hand, and the Vainshtein mechanism on the other hand. © 2013 IOP Publishing Ltd. Source


Kadota Y.,RIKEN | Shirasu K.,RIKEN | Guerois R.,CEA Saclay Nuclear Research Center | Guerois R.,French National Center for Scientific Research
Trends in Biochemical Sciences | Year: 2010

The NLR (nucleotide-binding domain and leucine-rich repeat containing) proteins provide pathogen-sensing systems that are conserved in both plants and animals. They can be activated directly or indirectly by pathogen-derived molecules through mechanisms that remain largely elusive. Studies in plants revealed that the molecular chaperone, HSP90, and its co-chaperones, SGT1 and RAR1, are major stabilizing factors for NLR proteins. More recent work indicates that SGT1 and HSP90 are also required for the function of NLR proteins in mammals, underscoring the evolutionary conservation of innate immune system regulatory mechanisms. Comparative analyses of plant and mammalian NLR proteins, together with recent insights provided by the structure of SGT1-HSP90 complex, have begun to uncover the mechanisms by which immune NLR sensors are regulated. © 2009 Elsevier Ltd. Source


Prospero J.M.,University of Miami | Landing W.M.,Florida State University | Schulz M.,CEA Saclay Nuclear Research Center
Journal of Geophysical Research: Atmospheres | Year: 2010

[1] Mineral dust plays an important role in ocean biogeochemistry as a source of Fe which in some regions is a limiting micronutrient. Ocean models often use the output of dust transport models to estimate dust-Fe deposition. However, models have not been adequately tested, because of the dearth of long-term dust deposition measurements. Here we present the results of a 3 year deposition study in a nine-station network in Florida which is impacted by African dust every year, and we compare these measurements with estimates from global dust models. Wet deposition (WD) and bulk deposition (BD) rates of soil-related elements (Al, Fe, and Mn) were highly correlated and remarkably uniform across the state; they exhibited an extremely strong summer maximum that closely matched concurrently measured dust concentrations in Miami. The average dust WD across the network was about 150 μg cm-2 yr-1, and the BD rate was 200 μg cm-2 yr-1. Dry deposition (DD), defined as the difference between BD and WD, was a minor component, about 20-30% of the total. In a comparison with nine dust models in the Aerosol Comparisons between Observations and Models project (AeroCom) database, models correctly characterized the seasonal cycle of deposition but most substantially underestimated summer deposition. The ratios of WD to DD in the models varied greatly, ranging from about 1:1 to 30:1 in contrast to the Florida Atmospheric Mercury Study station ratio, which was about 3:1 to 4:1. These results show a clear need for more dust deposition measurements in regions dominated by oceanic air masses and for a better understanding of the treatment of deposition processes in models. © 2010 by the American Geophysical Union. Source


Kirilovsky D.,CEA Saclay Nuclear Research Center | Kirilovsky D.,French National Center for Scientific Research | Kerfeld C.A.,Joint Genome Institute | Kerfeld C.A.,University of California at Berkeley
Biochimica et Biophysica Acta - Bioenergetics | Year: 2012

Photoprotective mechanisms have evolved in photosynthetic organisms to cope with fluctuating light conditions. Under high irradiance, the production of dangerous oxygen species is stimulated and causes photo-oxidative stress. One of these photoprotective mechanisms, non photochemical quenching (qE), decreases the excess absorbed energy arriving at the reaction centers by increasing thermal dissipation at the level of the antenna. In this review we describe results leading to the discovery of this process in cyanobacteria (qE cya), which is mechanistically distinct from its counterpart in plants, and recent progress in the elucidation of this mechanism. The cyanobacterial photoactive soluble orange carotenoid protein is essential for the triggering of this photoprotective mechanism. Light induces structural changes in the carotenoid and the protein leading to the formation of a red active form. The activated red form interacts with the phycobilisome, the cyanobacterial light-harvesting antenna, and induces a decrease of the phycobilisome fluorescence emission and of the energy arriving to the reaction centers. The orange carotenoid protein is the first photoactive protein to be identified that contains a carotenoid as the chromophore. Moreover, its photocycle is completely different from those of other photoactive proteins. A second protein, called the Fluorescence Recovery Protein encoded by the slr1964 gene in Synechocystis PCC 6803, plays a key role in dislodging the red orange carotenoid protein from the phycobilisome and in the conversion of the free red orange carotenoid protein to the orange, inactive, form. This protein is essential to recover the full antenna capacity under low light conditions after exposure to high irradiance. This article is part of a Special Issue entitled: Photosystem II. © 2011 Elsevier B.V. All rights reserved. Source


Mehtar-Tani Y.,CEA Saclay Nuclear Research Center | Milhano J.G.,University of Lisbon | Milhano J.G.,CERN | Tywoniuk K.,University of Barcelona
International Journal of Modern Physics A | Year: 2013

Jets are expected to play a prominent role in the ongoing efforts to characterize the hot and dense QCD medium created in ultrarelativistic heavy-ion collisions. The success of this program depends crucially on the existence of a full theoretical account of the dynamical effects of the medium on the jets that develop within it. By focussing on the discussion of the essential ingredients underlying such a theoretical formulation, we aim to set the appropriate context in which current and future developments can be understood. © 2013 World Scientific Publishing Company. Source


Procureur S.,CEA Saclay Nuclear Research Center
Modern Physics Letters A | Year: 2013

Modern experiments in hadronic physics require excellent detection and tracking capabilities in very high flux environment. Probing the quark and gluon content of the nucleon indeed necessitates semi-inclusive or exclusive reactions with very small cross-sections. Micromegas detectors have therefore been rapidly identified as natural candidates to equip the hottest region of the COMPASS spectrometer at CERN. Benefitting from several years of smooth operation at COMPASS, the Micromegas have been proposed to equip the future central tracker of the CLAS12 experiment at the Jefferson Laboratory. This project triggered an important R&D on the bulk and resistive technologies and inspired several projects involving cylindrical trackers. This paper focuses on the design and performance of the COMPASS and CLAS12 Micromegas, and reviews the R&D made on the discharge reduction in large hadron fluxes. © 2013 World Scientific Publishing Company. Source


Liu J.T.,University of Michigan | Minasian R.,CEA Saclay Nuclear Research Center
Nuclear Physics B | Year: 2013

The first quantum correction to the IIA string effective action arises at the eight-derivative level and takes the schematic form (t8t8-18ε10ε10)R4+B2∧X8. This correction, however, cannot be complete by itself, as it is neither supersymmetric nor T-duality covariant. We reexamine these eight-derivative couplings and conjecture that the simple replacement R→R(Ω+), where Ω+=Ω+12H is the connection with torsion, nearly completely captures their dependence on the B field. The exception is in the odd-odd spin structure sector, where additional terms are needed. We present here a complete result at the level of the five-point function and a partial one for the six-point function. Further evidence for this conjecture comes from considering T-duality as well as heterotic/IIA duality beyond leading order. Finally, we discuss the eleven-dimensional lift of the modified one-loop type IIA couplings. © 2013 Elsevier B.V. Source


Joyez P.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2013

We derive microscopically the dynamics associated with the dc Josephson effect in a superconducting tunnel junction interacting with an arbitrary electromagnetic environment. To do so, we extend to superconducting junctions the so-called P(E) theory (see, e.g., Ingold and Nazarov, arXiv:cond-mat/ 0508728) that accurately describes the interaction of a nonsuperconducting tunnel junction with its environment. We show the dynamics of this system is described by a small set of coupled correlation functions that take into account both Cooper pair and quasiparticle tunneling. When the phase fluctuations are small the problem is fully solved self-consistently, using and providing the exact linear admittance Y(ω) of the interacting junction. © 2013 American Physical Society. Source


Biroli G.,CEA Saclay Nuclear Research Center | Karmakar S.,Tata Institute of Fundamental Research | Procaccia I.,Weizmann Institute of Science
Physical Review Letters | Year: 2013

The dramatic dynamic slowing down associated with the glass transition is considered by many to be related to the existence of a static length scale that grows when temperature decreases. Defining, identifying, and measuring such a length is a subtle problem. Recently, two proposals, based on very different insights regarding the relevant physics, were put forward. One approach is based on the point-to-set correlation technique and the other on the scale where the lowest eigenvalue of the Hessian matrix becomes sensitive to disorder. Here we present numerical evidence that the two approaches might result in the same identical length scale. This provides mutual support for their relevance and, at the same time, raises interesting theoretical questions, discussed in the conclusion. © 2013 American Physical Society. Source


Bertrand J.B.,National Research Council Canada | Worner H.J.,ETH Zurich | Salieres P.,CEA Saclay Nuclear Research Center | Villeneuve D.M.,National Research Council Canada | Corkum P.B.,National Research Council Canada
Nature Physics | Year: 2013

High-harmonic spectroscopy uses attosecond techniques to measure single-atom or molecule photorecombination cross-sections. Whereas the amplitude of the extreme-ultraviolet light is easily measurable, the phase is more challenging to access. However, the phase contains information necessary for tomographic imaging of the molecular orbital wavefunction with attosecond-ångström resolution. Present techniques cannot simultaneously measure the phase as a function of molecular angle and photon frequency, which is necessary for a full reconstruction of the wavefunction. We overcome this limitation with an all-optical method that does not require any ad hoc assumptions about the phase. We apply it to record the full phase map of aligned bromine molecules relative to reference xenon atoms. It allows us to resolve, both spectrally and angularly, the participation of multiple molecular orbitals, and infer a phase of ionization. This method opens a path to time-resolved molecular orbital tomography. © 2013 Macmillan Publishers Limited. All rights reserved. Source


Huang Z.,CEA Saclay Nuclear Research Center | Vernizzi F.,French National Center for Scientific Research
Physical Review Letters | Year: 2013

We compute the cosmic microwave background temperature bispectrum generated by nonlinearities at recombination on all scales. We use CosmoLib2nd, a numerical Boltzmann code at second order to compute cosmic microwave background bispectra on the full sky. We consistently include all effects except gravitational lensing, which can be added to our result using standard methods. The bispectrum is peaked on squeezed triangles and agrees with the analytic approximation in the squeezed limit at the few percent level for all the scales where this is applicable. On smaller scales, we recover previous results on perturbed recombination. For cosmic-variance limited data to l max=2000, its signal-to-noise ratio is S/N=0.47, corresponding to fNLeff=-2.79, and will bias a local signal by fNLloc 0.82. © 2013 American Physical Society. Source


Calvet D.,CEA Saclay Nuclear Research Center
IEEE Transactions on Nuclear Science | Year: 2014

This paper presents the design and performance of a readout system for gaseous and silicon detectors built for the Minos nuclear physics experiment. A major constraint was to provide a multi-thousand channel, high performance readout system with low manpower effort and tight cost. This was achieved by the re-use of some earlier ASIC and front-end card (FEC) developments, the design of a new digital readout card, called the Feminos, and the use of commercial off-the-shelf components. The proposed system fully exploits the capability of the existing 72-channel AFTER chip designed for the T2K experiment and allows seamless migration to the 64-channel AGET chip, a pin-compatible evolution under production by the GET collaboration. The Feminos is a low complexity card designed to read out a FEC equipped with four AFTER chips (T2K model) or a newly assembled FEC populated with four AGET chips. The trigger clock module (TCM) is a synchronization board that allows system scaling up to 6912 channels with 24 Feminos and FECs, a commercial Gigabit Ethernet switch, and a data acquisition PC. The design of the Feminos hardware, firmware and embedded software are detailed and it is explained how high performance, rapid development and low cost were reached. System operation and data acquisition throughput scaling with multiple Feminos are investigated. © 1963-2012 IEEE. Source


Huang Y.-T.,University of Michigan | Huang Y.-T.,University of California at Los Angeles | Johansson H.,CERN | Johansson H.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2013

We show that three-dimensional supergravity amplitudes can be obtained as double copies of either three-algebra super-Chern-Simons matter theory or two-algebra super-Yang-Mills theory when either theory is organized to display the color-kinematics duality. We prove that only helicity-conserving four-dimensional gravity amplitudes have nonvanishing descendants when reduced to three dimensions, implying the vanishing of odd-multiplicity S-matrix elements, in agreement with Chern-Simons matter theory. We explicitly verify the double-copy correspondence at four and six points for N=12,10,8 supergravity theories and discuss its validity for all multiplicity. © 2013 American Physical Society. Source


Drummond J.M.,University of Savoy | Henn J.,University of Savoy | Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Nuclear Physics B | Year: 2013

We develop a manifestly supersymmetric version of the generalized unitarity cut method for calculating scattering amplitudes in N=4 SYM theory. We illustrate the power of this method by computing the one-loop n-point NMHV super-amplitudes. The result confirms two conjectures which we made in Drummond, et al., [1]. Firstly, we derive the compact, manifestly dual superconformally covariant form of the NMHV tree amplitudes for arbitrary number and types of external particles. Secondly, we show that the ratio of the one-loop NMHV to the MHV amplitude is dual conformal invariant. © 2012 Elsevier B.V. Source


Reiller P.E.,CEA Saclay Nuclear Research Center
Mineralogical Magazine | Year: 2012

Iron oxides and oxyhydroxides are commonly of considerable importance in the sorption of ions onto rocks, soils and sediments. They can be the controlling sorptive phases even if they are present in relatively small quantities. In common with other oxides and clay minerals, the sorption pH-edge of metals is directly linked to their hydrolysis: the higher the residual charge on the metal ion, the lower the pH-edge. Modelling of this process has been successfully carried out using different microscopic or macroscopic definitions of the interface (e.g. surface complexation or ion exchange models that may or may not include mineralogical descriptions). The influence of organic material on the sorption of many metals is of significant. This organic material includes simple organic molecules and more complex exopolymeric substances (e.g. humic substances) produced by the decay of natural organic matter. Sorption of this organic material to mineral surfaces has been the subject of a large body of work. The various types of organic substances do not share the same affinities for mineral surfaces in general, and for iron oxides and oxyhydroxides in particular. In those cases in which successful models of the component binary systems (i.e. metal-surface, metal-organic, organic-surface) have been developed, the formation of mixed surface complexes, the evolution of the surface itself, the addition order in laboratory systems, and the evolution of natural organic matter fractions during sorption, have often precluded a satisfactory description of metal-surface-organic ternary systems over a sufficiently wide range of parameter values (i.e. pH, ionic strength, concentration of humic substances). This manuscript describes the reasons for some successes and failures in the modelling of the ternary systems. Promising recent advances and possible methods of providing more complete descriptions of these intricate systems are also discussed. © 2012 The Mineralogical Society. Source


Luzum M.,CEA Saclay Nuclear Research Center
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

Making use of recently released data on dihadron correlations by the STAR Collaboration, I analyze the long-range ("ridge-like") part of these data and show that the dependence on both transverse momentum as well as orientation with respect to the event plane are consistent with correlations expected from only collective flow. In combination with previously analyzed centrality-dependent data, they provide strong evidence that only collective flow effects are present at large relative pseudorapidity. In contrast, by analyzing a "background subtracted" signal, the authors presenting the new data concluded that the ridge-like part of the measured correlation could not in fact be entirely generated from collective flow of the medium. I explain the discrepancy and illustrate some pitfalls of using the ZYAM prescription to remove flow background. © 2011 Elsevier B.V. Source


Aly J.-J.,CEA Saclay Nuclear Research Center
Physics of Plasmas | Year: 2011

We establish some general properties of a 3D isodynamic magnetostatic equilibrium admitting a family of nested toroidal flux surfaces. In particular, we use the virial theorem to prove a simple relation between the total pressure (magnetic + thermal) and the magnetic pressure on each flux surface, and we derive some useful consequences of the latter. We also show the constancy on each rational surface of two integrals along magnetic lines. As a simple application of our results, we show the nonexistence of an equilibrium with vanishing toroidal current, and of an equilibrium with closed lines. © 2011 American Institute of Physics. Source


Skarlatos A.,CEA Saclay Nuclear Research Center | Theodoulidis T.,University of Western Macedonia
IEEE Transactions on Magnetics | Year: 2010

The complex impedance of an air-cored coil in a conductive tube with eccentric inner and outer cylindrical surfaces is calculated. The analytic expressions for the induced fields and the impedance variation due to the eddy-current flow inside the tube wall are derived using a second-order potential approach. The addition theorem of Bessel functions is employed to perform the transition between the local coordinate systems that conform to the boundaries of the structure. Although the model can be used for any coil shape and orientation, we focus our study on the configuration of a bobbin coil with axis parallel to the axes of the tube surfaces, but not necessarily coinciding with either of them. The results of the presented analysis are verified by a finite-element-method (FEM) solution. © 2006 IEEE. Source


Giordano M.,University of Zaragoza | Peschanski R.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2011

We perform the analysis of quark-antiquark Reggeon exchange in meson-meson scattering, in the framework of the gauge/gravity correspondence in a confining background. On the gauge theory side, Reggeon exchange is described as quark-antiquark exchange in the t channel between fast projectiles. The corresponding amplitude is represented in terms of Wilson loops running along the trajectories of the constituent quarks and antiquarks. The paths of the exchanged fermions are integrated over, while the "spectator" fermions are dealt with in an eikonal approximation. On the gravity side, we follow a previously proposed approach, and we evaluate the Wilson-loop expectation value by making use of gauge/gravity duality for a generic confining gauge theory. The amplitude is obtained in a saddle-point approximation through the determination near the confining horizon of a Euclidean "minimal surface with floating boundaries", i.e., by fixing the trajectories of the exchanged quark and antiquark by means of a minimisation procedure, which involves both area and length terms. After discussing, as a warm-up exercise, a simpler problem on a plane involving a soap film with floating boundaries, we solve the variational problem relevant to Reggeon exchange, in which the basic geometry is that of a helicoid. A compact expression for the Reggeon-exchange amplitude, including the effects of a small fermion mass, is then obtained through analytic continuation from Euclidean to Minkowski space-time. We find in particular a linear Regge trajectory, corresponding to a Regge-pole singularity supplemented by a logarithmic cut induced by the non-zero quark mass. The analytic continuation leads also to companion contributions, corresponding to the convolution of the same Reggeon-exchange amplitude with multiple elastic rescattering interactions between the colliding mesons. Source


Blaizot J.-P.,CEA Saclay Nuclear Research Center | Ipp A.,Vienna University of Technology | Wschebor N.,University of the Republic of Uruguay
Nuclear Physics A | Year: 2011

We apply to the calculation of the pressure of a hot scalar field theory a method that has been recently developed to solve the Non-Perturbative Renormalization Group. This method yields an accurate determination of the momentum dependence of n-point functions over the entire momentum range, from the low momentum, possibly critical, region up to the perturbative, high momentum region. It has therefore the potential to account well for the contributions of modes of all wavelengths to the thermodynamical functions, as well as for the effects of the mixing of quasiparticles with multi-particle states. We compare the thermodynamical functions obtained with this method to those of the so-called Local Potential Approximation, and we find extremely small corrections. This result points to the robustness of the quasiparticle picture in this system. It also demonstrates the stability of the overall approximation scheme, and this up to the largest values of the coupling constant that can be used in a scalar theory in 3+1 dimensions. This is in sharp contrast to perturbation theory which shows no sign of convergence, up to the highest orders that have been recently calculated. © 2010 Elsevier B.V. Source


Lee H.K.,Hanyang University | Park B.-Y.,Chungnam National University | Rho M.,Hanyang University | Rho M.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2011

In a previous article, the four-dimensional (4D) half-Skyrmion (or five-dimensional dyonic salt) structure of dense baryonic matter described in crystalline configuration in the large Nc limit was shown to have nontrivial consequences on how antikaons behave in compressed nuclear matter with a possible implication for the "ice-9" phenomenon of deeply bound kaonic matter and condensed kaons in compact stars. We extend the analysis to make a further prediction on the scaling properties of hadrons that have a surprising effect on the nuclear tensor forces, the symmetry energy, and hence on the phase structure at high density. We treat this problem, relying on certain topological structures of chiral solitons. Combined with what can be deduced from hidden local symmetry for hadrons in a dense medium and the "soft" dilatonic degree of freedom associated with the trace anomaly of QCD, we uncover a novel structure of chiral symmetry in the "supersoft" symmetry energy that can influence the structure of neutron stars. © 2011 American Physical Society. Source


Konstandin T.,CERN | No J.M.,CEA Saclay Nuclear Research Center
Journal of Cosmology and Astroparticle Physics | Year: 2011

We discuss a hydrodynamic obstruction to bubble wall acceleration during a cosmological first-order phase transition. The obstruction results from the heating of the plasma in the compression wave in front of the phase transition boundary. We provide a simple criterion for the occurrence of the obstruction at subsonic bubble wall velocity in terms of the critical temperature, the phase transition temperature, and the latent heat of the model under consideration. The criterion serves as a sufficient condition of subsonic bubble wall velocities as required by electroweak baryogenesis. © 2011 IOP Publishing Ltd and SISSA. Source


Jeong W.,Ewha Womans University | Bae S.H.,Ewha Womans University | Toledano M.B.,CEA Saclay Nuclear Research Center | Rhee S.G.,Ewha Womans University
Free Radical Biology and Medicine | Year: 2012

Peroxiredoxins (Prxs) constitute a family of peroxidases in which cysteine serves as the primary site of oxidation during the reduction of peroxides. Members of the 2-Cys Prx subfamily of Prxs (Prx I to IV in mammals) are inactivated via hyperoxidation of the active-site cysteine to sulfinic acid (Cys-SO2H) during catalysis and are reactivated via an ATP-consuming reaction catalyzed by sulfiredoxin (Srx). This reversible hyperoxidation reaction has been proposed to protect H2O2 signaling molecules from premature removal by 2-Cys Prxs or to upregulate the chaperone function of these enzymes. In addition to its sulfinic acid reductase activity, Srx catalyzes the removal of glutathione (deglutathionylation) from modified proteins. The physiological relevance of both the reversible hyperoxidation of 2-Cys Prxs and the deglutathionylation catalyzed by Srx remains unclear. Recent findings have revealed that Srx expression is induced in mammalian cells under a variety of conditions, such as in metabolically stimulated pancreatic β cells, in immunostimulated macrophages, in neuronal cells engaged in synaptic communication, in lung cells exposed to hyperoxia or cigarette smoke, in hepatocytes of ethanol-fed animals, and in several types of cells exposed to chemopreventive agents. Such induction of Srx in mammalian cells is regulated at the transcriptional level, predominantly via activator protein-1 and/or nuclear factor erythroid 2-related factor 2. Srx expression is also regulated at the translational level in Saccharomyces cerevisiae. © 2012 Elsevier Inc. All rights reserved. Source


Soyez G.,CEA Saclay Nuclear Research Center
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We compute the ratio of the inclusive jet cross-sections obtained with the same jet algorithm at two different values of the jet radius. We perform a computation of that observable at NLO (O(?s2)) in perturbative QCD and compute non-perturbative corrections from soft-gluon emission. We discuss predictions for RHIC and the LHC. © 2011 Elsevier B.V. Source


Luzum M.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2011

I compare the first viscous hydrodynamic prediction for integrated elliptic flow in Pb-Pb collisions at the Large Hadron Collider with the first data released by the ALICE Collaboration. These new data are found to be consistent with hydrodynamic extrapolations of the Relativistic Heavy-Ion Collider data with no change in medium parameters (e.g., average viscosity). I also discuss how, in general, a precise comparison of data to theoretical calculations requires an understanding of some subtleties of the measurement-most notably the cut on transverse momentum of the particles used and the differing sensitivities to flow fluctuations and nonflow effects of the various measurement methods. © 2011 American Physical Society. Source


Blaizot J.P.,CEA Saclay Nuclear Research Center
Nuclear Physics A | Year: 2011

This is a personal summary of the meeting "Saturation, the Color Glass Condensate and Glasma: What Have we Learned from RHIC?" that took place at BNL in May 2010. The purpose of the meeting was to discuss the status of high density QCD and parton saturation, and to review the progress that RHIC has allowed in the field. © 2011 Elsevier B.V. Source


Guica M.,CEA Saclay Nuclear Research Center | Strominger A.,Jefferson Lab
Journal of High Energy Physics | Year: 2011

Supersymmetric M/string compactifications to five dimensions contain BPS black string solutions with magnetic graviphoton charge P and near-horizon geometries which are quotients of AdS3 × S2. The holographic duals are typically known 2D CFTs with central charges cL = cR = 6P3 for large P. These same 5D compactifications also contain non-BPS but extreme Kerr-Newman black hole solutions with SU(2)L spin JL and electric graviphoton charge Q obeying Q3 ≤ JL2. It is shown that in the maximally charged limit Q3 → JL2, the near-horizon geometry coincides precisely with the right-moving temperature TR = 0 limit of the black string with magnetic charge P = JL1/3. The known dual of the latter is identified as the cL = cR = 6JL CFT predicted by the Kerr/CFT correspondence. Moreover, at linear order away from maximality, one finds a TR ≠ 0 quotient of the AdS3 factor of the black string solution and the associated thermal CFT entropy reproduces the linearly sub-maximal Kerr-Newman entropy. Beyond linear order, for general Q3 < JL2, one has a finite-temperature quotient of a warped deformation of the magnetic string geometry. The corresponding dual deformation of the magnetic string CFT potentially supplies, for the general case, the cL = cR = 6JL CFT predicted by Kerr/CFT. © SISSA 2011. Source


Santolini J.,CEA Saclay Nuclear Research Center
Journal of Inorganic Biochemistry | Year: 2011

Since its discovery, nitric oxide synthase (NOS), the enzyme responsible for NO biosynthesis in mammals, has been the subject of extensive investigations regarding its catalytic and molecular mechanisms. These studies reveal the high degree of sophistication of NOS functioning and regulation. However, the precise description of the NOS molecular mechanism and in particular of the oxygen activation chemistry is still lacking. The reaction intermediates implicated in NOS catalysis continue to elude identification and the current working paradigm is increasingly contested. Consequently, the last three years has seen the emergence of several competing models. All these models propose the same global reaction scheme consisting of two successive oxidation reactions but they diverge in the details of their reaction sequence. The major discrepancies concern the number, source and characteristics of proton and electron transfer processes. As a result each model proposes distinct reaction pathways with different implied oxidative species. This review aims to examine the different experimental evidence concerning NOS proton and electron transfer events and the role played by the substrates and cofactors in these processes. The resulting discussion should provide a comparative picture of all potential models for the NOS molecular mechanism. © 2010 Elsevier Inc. Source


Guarne A.,McMaster University | Charbonnier J.-B.,CEA Saclay Nuclear Research Center | Charbonnier J.-B.,French National Center for Scientific Research
Progress in Biophysics and Molecular Biology | Year: 2015

DNA mismatch repair (MMR) is a conserved pathway that safeguards genome integrity by correcting replication errors. The coordinated actions of two proteins (MutS and MutL) initiate the mismatch repair response and defects in the genes encoding for these proteins have been linked to sporadic and hereditary cancers. The basic steps to repair a mismatch include recognizing the mismatch, discriminating the newly synthesized from the parental strand, removing and re-synthesizing the erroneous strand. Although the DNA mismatch repair pathway has been extensively studied over the last four decades, the strand discrimination mechanism has remained elusive in most organisms. Work over the last decade has brought significant progress onto this step of the pathway, in turn ascribing new and critical roles to the MutL protein. In this review, we describe biochemical, biophysical and structural analyses that have clarified how MutL aids at discriminating the newly synthesized strand from its template and marking it for removal. © 2015. Source


Grozin A.,Novosibirsk State University | Henn J.M.,Institute for Advanced Study | Korchemsky G.P.,CEA Saclay Nuclear Research Center | Marquard P.,German Electron Synchrotron
Physical Review Letters | Year: 2015

We present the full analytic result for the three loop angle-dependent cusp anomalous dimension in QCD. With this result, infrared divergences of planar scattering processes with massive particles can be predicted to that order. Moreover, we define a closely related quantity in terms of an effective coupling defined by the lightlike cusp anomalous dimension. We find evidence that this quantity is universal for any gauge theory and use this observation to predict the nonplanar nf-dependent terms of the four loop cusp anomalous dimension. © 2015 American Physical Society. Source


Kim K.-S.,Pohang University of Science and Technology | Pepin C.,CEA Saclay Nuclear Research Center | Pepin C.,Federal University of Rio Grande do Norte
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We present a series of arguments showing that the Seebeck coefficient can be used as a decisive experiment to characterize the nature of the quantum-critical point (QCP) in heavy fermion compounds. Being reactive almost exclusively to the presence of delocalized entropic carriers, the Seebeck coefficient shows a drastic collapse at the Kondo breakdown QCP, as the reconstruction of the Fermi surface takes place. In contrast, around a spin-density-wave QCP, the Seebeck coefficient is broadly symmetric. We discuss the possibility of a change of sign at the QCP, the characteristic variation in | S/T | with temperature and external parameter, as well as the capacity of the Seebeck coefficient to distinguish between localized and itinerant antiferromagnetism. Suggestions of experiments are given in the case of four nonconventional compounds: YbRh2 Si2, Ce (Mn) In 5, CeCu6-x Aux, and URu2 Si 2. © 2010 The American Physical Society. Source


Monthus C.,CEA Saclay Nuclear Research Center
Journal of Statistical Mechanics: Theory and Experiment | Year: 2015

For the quantum Ising chain, the self-dual block renormalization procedure of Fernandez-Pacheco (1979 Phys. Rev. D 19 3173) is known to reproduce exactly the location of the zero-temperature critical point and the correlation length exponent ν = 1. Recently, Miyazaki and Nishimori (2013 Phys. Rev. E 87 032154) have proposed to study the disordered quantum Ising model in dimensions d > 1 by applying the Fernandez-Pacheco procedure successively in each direction. To avoid the inequivalence of directions of their approach, we propose here an alternative procedure where the d directions are treated on the same footing. For the pure model, this leads to the correlation length exponents ν ≃ 0.625 in d = 2 (to be compared with the 3D classical Ising model exponent ν ≃ 0.63) and ν ≃ 0.5018 (to be compared with the 4D classical Ising model mean-field exponent ν = 1/2). For the disordered model in dimension d = 2, either ferromagnetic or spin-glass, the numerical application of the renormalization rules to samples of linear size L = 4096 yields that the transition is governed by an Infinite Disorder Fixed Point, with the activated exponent ψ ≃ 0.65, the typical correlation exponent νtyp ≃ 0.44 and the finitesize correlation exponent νFS ≃ 1.25. We discuss the similarities and differences with the Strong Disorder Renormalization results. © 2015 IOP Publishing Ltd and SISSA Medialab srl. Source


Auzanneau F.,CEA Saclay Nuclear Research Center
Electronics Letters | Year: 2016

A new reflectometry-based wire diagnosis method using chaotic signa ls is presented. It shows excellent pote ntial for the diagnosis of live wires (i.e. durin g their operational usage) and complex topology network s. The use of chaotic signals for distributed diagnosis and the detection of defects in wires is investigated. Chaos time-domain Refl ectometry (CTDR) using low auto-correlation sidelobes signals, shows high performances in very noisy environment: the detection and location of hard defects are possible, even if several refl ectometers inject their signals concurrently with th e di agnosis and the norm al operation of the cable. This enables using CTDR for distributed diagnosis of complex topology networks. © 2016 The Institution of Engineering and Technology. Source


Thuery P.,CEA Saclay Nuclear Research Center
Crystal Growth and Design | Year: 2011

The reaction of uranyl nitrate with cucurbit[6]uril (CB6) under hydrothermal conditions and in the presence of alkali metal ion nitrates has been investigated. Two complexes with Na + have been obtained, [Na 3(CB6)(H 2O) 8][(UO 2) 2(OH) 2(NO 3) 4]·NO 3·2H 2O (1) and [Na 1.5(CB6)(H 2O) 4][(UO 2) 6O 2(OH) 6(HCOO) 3.5(H 2O)]·8H 2O (2), which differ by the presence in the latter of formate ions due to the hydrolysis of the dimethylformamide cosolvent. Both 1 and 2 display columnar, cationic Na +-CB6 complexes, with independent, anionic dinuclear (1) or one-dimensional polymeric (2) uranyl complexes. The molecular species [(UO 2) 3K 3O 1.5(OH) 3(HCOO) 3(CB6) 3(H 2O) 6(DMF) 3]·3H 2O (3) is an original arrangement in which three K + ions assemble three CB6 molecules around a trigonal axis and are themselves bound to the terminal oxo groups of a μ 3-oxo- centered uranyl trinuclear unit. Only in the case of the cesium-containing complex [(UO 2) 2Cs 2(OH) 3(CB6)(H 2O) 4][(UO 2) 2Cs 2(OH) 3(NO 3) 2(CB6)(H 2O) 2][(UO 2) 2(OH) 2(NO 3) 4]·2NO 3·10H 2O (4) is uranyl coordination to CB6 observed, resulting in the formation of columns with alternate CB6 molecules and [(UO 2) 2Cs 2(OH) 2] 4+ heterotetranuclear units held by two μ 3-hydroxo ions. 4,5-Dihydroxy-1,3-benzenedisulfonic acid (Tiron, H 4tir) was used as an additional ligand so as to create bridges between the uranyl and alkali metal ions. Its disodium salt yielded the complexes [UO 2Na 3(Htir)(CB6)(H 2O) 11][UO 2(Htir)(H 2O) 3]·NO 3·11H 2O (5) and [(UO 2) 2Na 2(Htir) 2(CB6)(H 2O) 8]·4H 2O (6), obtained at room temperature and under hydrothermal conditions, respectively. Uranyl is chelated in both cases by one phenoxide and one sulfonate oxygen atoms. Whereas 5 is once more a columnar arrangement, with the uranyl complex units bound on either side, 6 is a two-dimensional assembly in which the uranyl ions are located on the outside of the sheets. Replacement of sodium by potassium ions gave the complex [(UO 2) 2K 2(Htir) 2(CB6)(H 2O) 8]·4H 2O (7), in which, notwithstanding its closeness to 6, the different connectivity due to the larger size of potassium ions brings about the formation of a three-dimensional framework. These results show the considerable variety of architectures which can be generated in the uranyl-cucurbituril system, depending on the presence of additional cations and ligands, and also the potential of sulfonates in uranyl coordination chemistry. © 2011 American Chemical Society. Source


Desvaux H.,CEA Saclay Nuclear Research Center
Progress in Nuclear Magnetic Resonance Spectroscopy | Year: 2013

The development of nuclear magnetic resonance spectroscopy for probing liquid-state systems primary results from its ability to exactly predict the evolution of the spin systems even under the influence of very complex pulse sequences. This remarkable feature of liquid-state NMR results from the linear time-domain evolution of the magnetization of a unique spin or more generally of the density matrix of a given molecule. This remarkable feature of liquid-state NMR results from the linear time-domain evolution of the magnetization of a unique spin or more generally of the density matrix of a given molecule. Radiation damping has been known from the early days of NMR. This non-linear interaction being mediated by the detecting coil, strongly depends on its coupling to the precessing magnetization. It is also dependent on the resonance frequency of the electronic circuit. The presence of RD can alter the signal resonance frequency, can forbid the magnetization inversion or can allow the detection of nuclear spin-noise. Source


Mallick K.,CEA Saclay Nuclear Research Center
Physica A: Statistical Mechanics and its Applications | Year: 2015

In these lectures, we shall present some remarkable results that have been obtained for systems far from equilibrium during the last two decades. We shall put a special emphasis on the concept of large deviation functions that provide us with a unified description of many physical situations. These functions are expected to play, for systems far from equilibrium, a role akin to that of the thermodynamic potentials. These concepts will be illustrated by exact solutions of the Asymmetric Exclusion Process, a paradigm for non-equilibrium statistical physics. © 2014 Elsevier B.V. All rights reserved. Source


Tagliabue A.,University of Liverpool | Aumont O.,Center Ird Of Bretagne | Bopp L.,CEA Saclay Nuclear Research Center
Geophysical Research Letters | Year: 2014

Variable supply of iron to the ocean is often invoked to explain part of past changes in atmospheric CO2 (CO2atm). Using model simulations, we find that CO2atm is sensitive on the order of 15, 2, and 1 ppm to sedimentary, dust, and hydrothermal iron input. CO2atm is insensitive to dust because it is not the major iron input to the Southern Ocean. Modifications to the relative export of Si(OH)4 to low latitudes are opposite to those predicted previously. Although hydrothermalism is the major control on the iron inventory in ∼25% of the ocean, it remains restricted to the deep ocean, with minor effects on CO2atm. Nevertheless, uncertainties regarding the iron-binding ligand pool can have significant impacts on CO2atm. Ongoing expansion of iron observations as part of GEOTRACES will be invaluable in refining these results. Key Points Atmospheric CO2 is relatively insensitive to changes to dust supply of iron Hydrothermal Fe is key to the iron inventory, but has a small effect on CO2 There are unexpected changes to Si cycling due to changes in Fe input ©2014. American Geophysical Union. All Rights Reserved. Source


Nikolovski J.-P.,CEA Saclay Nuclear Research Center
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2013

Tactile sensing is widely used in human-computer interfaces. However, mechanical integration of touch technologies is often perceived as difficult by engineers because it often limits the freedom of style or form factor requested by designers. Recent work in active ultrasonic touch technologies has made it possible to transform thin glass plates, metallic sheets, or plastic shells into interactive surfaces. The method is based on a learning process of touch-induced, amplitude-disturbed diffraction patterns. This paper proposes, first, an evolution in the design with multiple dipole transducers that improves touch sensitivity or maximum panel size by a factor of ten, and improves robustness and usability in moderately reverberant panels, and second, defines a set of acoustic variables in the signal processing for the evaluation of sensitivity and radiating features. For proof of concept purposes, the design and process are applied to 3.2-and 6-mm-thick glass plates with variable damping conditions. Transducers are bonded to only one short side of the rectangular substrates. Measurements show that the highly sensitive free lateral sides are perfectly adapted for pinch-touch and pinch-slide interactions. The advantage of relative versus absolute touch disturbance measurement is discussed, together with tolerance to abutting contaminants. © 2013 IEEE. Source


Eynard B.,CEA Saclay Nuclear Research Center | Orantin N.,University of Lisbon
Communications in Mathematical Physics | Year: 2015

The BKMP conjecture (2006–2008) proposed a new method to compute closed and open Gromov–Witten invariants for every toric Calabi–Yau 3-folds, through a topological recursion based on mirror symmetry. So far, this conjecture has been verified to low genus for several toric CY3folds, and proved to all genus only for (Formula presented.). In this article we prove the general case. Our proof is based on the fact that both sides of the conjecture can be naturally written in terms of combinatorial sums of weighted graphs: on the A-model side this is the localization formula, and on the B-model side the graphs encode the recursive algorithm of the topological recursion. One can slightly reorganize the set of graphs obtained in the B-side, so that it coincides with the one obtained by localization in the A-model. Then it suffices to compare the weights of vertices and edges of graphs on each side, which is done in two steps: the weights coincide in the large radius limit, due to the fact that the toric graph is the tropical limit of the mirror curve. Then the derivatives with respect to Kähler radius coincide due to the special geometry property implied by the topological recursion. © 2015, Springer-Verlag Berlin Heidelberg. Source


A series of nine complexes has been obtained from the hydrothermal reaction of uranyl nitrate with long-chain alkyldicarboxylic acids (HOOC-(CH 2) n-2-COOH, denoted H 2Cn) in the presence of cucurbit[6]uril (CB6), dimethylformamide (DMF), which generates dimethylammonium cations in situ, and additional alkaline-earth metal ions in some cases. The crystal structures of the three complexes [H 2NMe 2] 2[(UO 2) 4O 2(OH) 2(C8) 2(CB6)]•8H 2O (1), [H 2NMe 2] 2[(UO 2) 4O 2(OH) 2(C9) 2(CB6)]•5H 2O (2), and [H 2NMe 2] 2[(UO 2) 4O 2(OH) 2(C9) 2(CB6)]•8H 2O (3) are closely related, since all contain the same tetranuclear motif held by two μ 3-oxo and two μ 2-hydroxo ions, and attached to CB6 by uranyl-O-carbonyl bonds. Two-dimensional assemblies are formed in 1 and 2 and a three-dimensional framework in 3. The cucurbituril molecule is not coordinated in compounds 4-9 but is present as a structure-directing agent. The complex [H 2NMe 2] 2[(UO 2) 4O 2(C6) 3]•CB8•8H 2O (4), in which cucurbit[8]uril (CB8) comes from the initial CB6, displays a stacking of planar uranyl-organic two-dimensional layers with sheets of CB8 molecules. An analogous overall arrangement involving one-dimensional ribbons based on a uranyl trinuclear motif is found in the complex [H 2NMe 2][(UO 2) 3O(OH) 2(C7)(HC7)(H 2O) 0.5]•CB6•4H 2O (5). A helicoidal one-dimensional polymer is formed in [H 2NMe 2] 4[(UO 2) 4(C10) 6]•CB6•H 2O (6), in which the packing is quite intricate. Finally, the last three complexes, [Ca 2(CB6)(H 2O) 7(DMF)][(UO 2) 8O 4(C8) 6(H 2O)]•6H 2O (7), [Sr 2(CB6)(H 2O) 7(DMF) 3][(UO 2) 6O 2(C8) 6]•2H 2O (8), and [Sr 2(CB6)(H 2O) 8(DMF) 2][(UO 2) 8O 4(C10) 6] (9), include columns built from alkaline-earth ion complexes with CB6, which are either molecular (7) or one-dimensional polymeric (8 and 9). In complexes 7 and 9, these columns are separated from one another and surrounded by the corrugated two-dimensional uranyl-organic assemblies, while, in 8, the latter are planar grids whose stacking defines channels in which the columns are nestled. These results provide new examples of the potential of cucurbiturils as uranyl complexants or as structure-directing agents. The sheets or columns readily formed by CBs, either free or complexed, appear as particularly well suited to associate with the two-dimensional or ribbon-like topologies most common among uranyl-organic species, which opens perspectives for the design of hybrid layered materials. © 2011 American Chemical Society. Source


Wu B.,CEA Saclay Nuclear Research Center
Nuclear and Particle Physics Proceedings | Year: 2016

I give a self-contained review on radiative p⊥-broadening and radiative energy loss of high-energy partons in QCD matter. The typical p2 ⊥ of high-energy partons receives a double logarithmic correction due to the recoiling effect of medium-induced gluon radiation. Such a double logarithmic term, averaged over the path length of the partons, can be taken as the radiative correction to the jet quenching parameter q and hence contributes to radiative energy loss. This has also been confirmed by detailed calculations of energy loss by radiating two gluons. © 2016 Elsevier B.V. Source


Dubail J.,Yale University | Stephan J.-M.,CEA Saclay Nuclear Research Center
Journal of Statistical Mechanics: Theory and Experiment | Year: 2011

We introduce the (logarithmic) bipartite fidelity of a quantum system A ∪ B as the (logarithm of the) overlap between its ground state wavefunction and the ground state that one would obtain if the interactions between two complementary subsystems A and B were switched off. We argue that it should typically satisfy an area law in dimension d > 1. In the case of one-dimensional quantum critical points (QCP) we find that it admits a universal scaling form, ∼ ln l, where l is the typical size of the smaller subsystem. The prefactor is proportional to the central charge c and depends on the geometry. We also argue that this quantity can be useful for locating quantum phase transitions, allows for a reliable determination of the central charge, and in general exhibits various properties that are similar to the entanglement entropy. Like the entanglement entropy, it contains subleading universal terms in the case of a 2D conformal QCP. © 2011 IOP Publishing Ltd. Source


Ogami S.,Ehime University | Boussac A.,CEA Saclay Nuclear Research Center | Sugiura M.,Ehime University | Sugiura M.,Japan Science and Technology Agency
Biochimica et Biophysica Acta - Bioenergetics | Year: 2012

The sensitivity to high light conditions of Photosystem II with either PsbA1 (WT*1) or PsbA3 (WT*3) as the D1 protein was studied in whole cells of the thermophilic cyanobacterium Thermosynechococcus elongatus. When the cells are cultivated under high light conditions the following results were found: (i) The O2 evolution activity decreases faster in WT*1 cells than in WT*3 cells both in the absence and in the presence of lincomycin, a protein synthesis inhibitor; (ii) In WT*1 cells, the rate constant for the decrease of the O2 evolution activity is comparable in the presence and in the absence of lincomycin; (iii) The D1 content revealed by western blot analysis decays similarly in both WT*1 and WT*3 cells and much slowly than O2 evolution; (iv) The faster decrease in O2 evolution in WT*1 than in WT*3 cells correlates with a much faster inhibition of the S2-state formation; (v) The shape of the WT*1 cells is altered. All these results are in agreement with a photo-inhibition process resulting in the loss of the O2 activity much faster than the D1 turnover in PsbA1-PSII and likely to a greater production of reactive oxygen species under high light conditions in WT*1 than in WT*3. This latter result is discussed in view of the known effects of the PsbA1 to PsbA3 substitution on the redox properties of the Photosystem II cofactors. The observation that under low light conditions WT*3 cells are able to express the psbA3 gene, whereas under similar conditions wild type cells are expressing mainly the psbA1 gene is also discussed. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. © 2011 Elsevier B.V. All rights reserved. Source


Longhin A.,CEA Saclay Nuclear Research Center
AIP Conference Proceedings | Year: 2010

An optimization of the CERN SPL neutrino beam line has been performed guided by the idea of employing a graphite target. The interactions of protons of kinetic energies of 2.2, 3.5, 4.5 and 8 GeV/c2 on a cylindrical 1.5 cm diameter carbon target have been simulated with FLUKA2008.3. Energy deposition and particle yields with mercury and carbon have been compared using for both materials a target lenght corresponding to about two hadronic interaction lengths. Power deposition and neutron fluxes are suppressed to a large extent with carbon. The transportation and decay of secondary mesons was done with GEANT3 in order to calculate the neutrino fluxes. Sensitivities were calculated with GLoBES assuming a beam power of 4 MW (HP-SPL) and a 440 ktons water Cherenkov detector (MEMPHYS) located at 130 km from the target in a new foreseen Fréjus laboratory. The obtained sensitivities with the carbon target are comparable to the ones achieved with the mercury target. The full simulation has been recently rewritten using GEANT4 which allows a higher degree of flexibility for arranging the horn geometries. A detailed comparison of the algorithms has been done and a good agreement is found for the final neutrino fluxes. A preliminary comparison of the sensitivities to sin2 2q13 and CP violation with an optimized horn are also presented. © 2010 American institute of Physics. Source


Sala F.,CEA Saclay Nuclear Research Center | Tesi A.,University of Chicago
Journal of High Energy Physics | Year: 2015

Abstract: The presence of extra scalar singlets is a feature of several motivated extensions of the Standard Model, and the mixing of such a singlet with the Higgs boson is allowed to be quite large by current experiments. In this paper we perform a thorough phenomeno-logical study of this possibility. We consider both direct and indirect searches, and we quantify the current constraints as well as the prospects for future hadron and lepton machines — from the forthcoming LHC run up to a futuristic 100 TeV proton-proton collider. The direct reaches are obtained extrapolating the current limits with a technique that we discuss and check with various tests. We find a strong complementarity between direct and indirect searches, with the former dominating for lower values of the singlet mass. We also find that the trilinear Higgs coupling can have sizeable deviations from its Standard Model value, a fact for which we provide an analytical understanding. The results are first presented in a general scalar singlet extension of the Standard Model, taking advantage of the very small number of parameters relevant for the phenomenology. Finally, we specify the same analysis to a few most natural models, i.e. the Next-to-Minimal Supersymmetric Standard Model, Twin Higgs and Composite Higgs. © 2015, The Author(s). Source


McNeil B.I.,University of New South Wales | Tagliabue A.,CEA Saclay Nuclear Research Center | Sweeney C.,University of Colorado at Boulder
Geophysical Research Letters | Year: 2010

Antarctic coastal waters have an abundance of marine organisms that secrete the mineral aragonite for growth and survival. Increasing oceanic anthropogenic CO2 uptake will push these waters to a point whereby aragonite will start to geochemically corrode, with direct consequences for the Antarctic ecosystem. Here we combine surface CO2 data in the Ross Sea, Antarctica with a regional ocean/sea-ice model to better pinpoint the timing of corrosive conditions. Our analysis suggests sea-ice cover and deep-water entrainment during winter results in 65% lower storage of anthropogenic CO 2 in comparison to atmospheric CO2 equilibrium. This means that instead of corrosive acidified waters beginning as early as the winter of 2015, anthropogenic CO2 disequilibrium delays its onset by up to 30 years, giving this Antarctic marine ecosystem a several decade reprieve to corrosive conditions. Our results demonstrate a broader importance of understanding natural oceanic carbon cycle variability for the onset of corrosive conditions. Copyright 2010 by the American Geophysical Union. Source


Kopp J.,Max Planck Institute for Nuclear Physics | Machado P.A.N.,University of Sao Paulo | Machado P.A.N.,CEA Saclay Nuclear Research Center | Maltoni M.,Institute Fisica Teorica UAM | Schwetz T.,Max Planck Institute for Nuclear Physics
Journal of High Energy Physics | Year: 2013

Neutrino oscillations involving eV-scale neutrino mass states are investigated in the context of global neutrino oscillation data including short and long-baseline accelerator, reactor, and radioactive source experiments, as well as atmospheric and solar neutrinos. We consider sterile neutrino mass schemes involving one or two mass-squared differences at the eV2 scale denoted by 3+1, 3+2, and 1+3+1. We discuss the hints for eV-scale neutrinos from ve (-) disappearance (reactor and Gallium anomalies) and vμ (-) → ve (-) appearance (LSND and MiniBooNE) searches, and we present constraints on sterile neutrino mixing from vμ (-) and neutral-current disappearance data. An explanation of all hints in terms of oscillations suffers from severe tension between appearance and disappearance data. The best compatibility is obtained in the 1+3+1 scheme with a p-value of 0.2% and exceedingly worse compatibilities in the 3+1 and 3+2 schemes. © 2013 SISSA. Source


An C.S.,CAS Institute of High Energy Physics | Saghai B.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2013

Background: Unravelling the role played by nonvalence flavors in baryons is crucial in deepening our comprehension of QCD. The strange quark, a component of the higher Fock states in baryons, is an appropriate tool to study nonperturbative mechanisms due to the pure sea quark. Purpose: Study the magnitude and the sign of the strangeness magnetic moment μs and the magnetic form factor (GMs) of the proton. Methods: Within an extended chiral constituent quark model, we investigate contributions from all possible five-quark components to μs and GMs(Q2) in the four-vector momentum range Q2≤1 (GeV/c)2. The probability of the strangeness component in the proton wave function is calculated employing the 3P0 model. Results: Predictions are obtained by using input parameters taken from the literature. The observables μs and GMs(Q2) are found to be small and negative, consistent with the lattice-QCD findings as well as with the latest data released by the PVA4 and HAPPEX Collaborations. Conclusions: Due to sizable cancellations among different configurations contributing to the strangeness magnetic moment of the proton, it is indispensable to (i) take into account all relevant five-quark components and include both diagonal and nondiagonal terms, (ii) handle with care the oscillator harmonic parameter ω5 and the ss̄ component probability. © 2013 American Physical Society. Source


Salieres P.,CEA Saclay Nuclear Research Center
Reports on progress in physics. Physical Society (Great Britain) | Year: 2012

The recently developed attosecond light sources make the investigation of ultrafast processes in matter possible with unprecedented time resolution. It has been proposed that the very mechanism underlying the attosecond emission allows the imaging of valence orbitals with Ångström space resolution. This controversial idea together with the possibility of combining attosecond and Ångström resolutions in the same measurements has become a hot topic in strong-field science. Indeed, this could provide a new way to image the evolution of the molecular electron cloud during, e.g. a chemical reaction in 'real time'. Here we review both experimental and theoretical challenges raised by the implementation of these prospects. In particular, we show how the valence orbital structure is encoded in the spectral phase of the recombination dipole moment calculated for Coulomb scattering states, which allows a tomographic reconstruction of the orbital using first-order corrections to the plane-wave approach. The possibility of disentangling multi-channel contributions to the attosecond emission is discussed as well as the necessary compromise between the temporal and spatial resolutions. Source


Massai S.,Arnold Sommerfeld Center for Theoretical Physics | Pasini G.,CEA Saclay Nuclear Research Center | Puhm A.,University of California at Santa Barbara
Journal of High Energy Physics | Year: 2015

We study the dynamics of probe M5 branes with dissolved M2 charge in bubbling geometries with SO(4) × SO(4) symmetry. These solutions were constructed by Bena-Warner and Lin-Lunin-Maldacena and correspond to the vacua of the maximally supersymmetric mass-deformed M2 brane theory. We find that supersymmetric probe M2 branes polarize into M5 brane shells whose backreaction creates an additional bubble in the geometry. We explicitly check that the supersymmetric polarization potential agrees with the one found within the Polchinski-Strassler approximation. The main result of this paper is that probe M2 branes whose orientation is opposite to the background flux can polarize into metastable M5 brane shells. These decay to a supersymmetric configuration via brane-flux annihilation. Our findings suggest the existence of metastable states in the mass-deformed M2 brane theory. © 2015, The Author(s). Source


Marsolier-Kergoat M.-C.,CEA Saclay Nuclear Research Center
PLoS ONE | Year: 2012

DNA replication was recently shown to induce the formation of compositional skews in the genomes of the yeasts Saccharomyces cerevisiae and Kluyveromyces lactis. In this work, I have characterized further GC and TA skew variations in the vicinity of S. cerevisiae replication origins and termination sites, and defined asymmetry indices for origin analysis and prediction. The presence of skew jumps at some termination sites in the S. cerevisiae genome was established. The majority of S. cerevisiae replication origins are marked by an oriented consensus sequence called ACS, but no evidence could be found for asymmetric origin firing that would be linked to ACS orientation. Asymmetry indices related to GC and TA skews were defined, and a global asymmetry index IGC,TA was described. IGC,TA was found to strongly correlate with origin efficiency in S. cerevisiae and to allow the determination of sets of intergenes significantly enriched in origin loci. The generalized use of asymmetry indices for origin prediction in naive genomes implies the determination of the direction of the skews, i.e. the identification of which strand, leading or lagging, is enriched in G and which one is enriched in T. Recent work indicates that in Candida albicans and in several related species, centromeres contain early and efficient replication origins. It has been proposed that the skew jumps observed at these positions would reflect the activity of these origins, thus allowing to determine the direction of the skews in these genomes. However, I show here that the skew jumps at C. albicans centromeres are not related to replication and that replication-associated GC and TA skews in C. albicans have in fact the opposite directions of what was proposed. © 2012 Marie-Claude Marsolier-Kergoat. Source


Carrasco J.J.M.,Stanford University | Johansson H.,CEA Saclay Nuclear Research Center
Journal of Physics A: Mathematical and Theoretical | Year: 2011

We review some recent additions to the tool-chest of techniques for finding compact integrand representations of multiloop gauge-theory amplitudes-including non-planar contributions-applicable for N = 4 super-YangMills in four and higher dimensions, as well as for theories with less supersymmetry. We discuss a general organization of amplitudes in terms of purely cubic graphs, review the method of maximal cuts, as well as some special D-dimensional recursive cuts, and conclude by describing the efficient organization of amplitudes resulting from the conjectured duality between color and kinematic structures on constituent graphs. © 2011 IOP Publishing Ltd. Source


Volin D.,CEA Saclay Nuclear Research Center | Volin D.,Pennsylvania State University
Journal of Physics A: Mathematical and Theoretical | Year: 2011

In this review, a general procedure to represent the integral Bethe Ansatz equations in the form of the Reimann-Hilbert problem is given. This allows us to study integrable spin chains in the thermodynamic limit in a simple way. Based on the functional equations we give the procedure that allows finding the subleading orders in the solution of various integral equations solved to the leading order by the Wiener-Hopf techniques. The integral equations are studied in the context of the AdS/CFT correspondence, where their solution allows for the verification of the integrability conjecture up to two loops of the strong coupling expansion. In the context of the two-dimensional sigma models we analyze the large-order behavior of the asymptotic perturbative expansion. The obtained experience with the functional representation of the integral equations also allowed us to solve explicitly the crossing equations that appear in the AdS/CFT spectral problem. © 2011 IOP Publishing Ltd. Source


Goubault E.,CEA Saclay Nuclear Research Center
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

This invited lecture is a survey of our work over the last 12 years or so, dealing with the precise analysis of numerical programs, essentially control programs such as the ones found in the aerospace, nuclear and automotive industry. Our approach is now based on a rather generic abstract domain, based on "zonotopes" or "affine forms" [7], but with some specificities. For instance, our zonotopic domain provides a functional abstraction [16,13], i.e. an abstraction of the input-output relationships between values of variables, allowing for test generation and modular verification [21]. Also, our domain deals with the real number and the finite precision (for instance, floating-point or fixed-point) semantics [14,17]. It is used in practice in FLUCTUAT [20,9,4] to prove some functional properties of programs, generate (counter-) examples, identify the discrepancy between the real number and the finite precision semantics and its origin etc. © 2013 Springer-Verlag. Source


Guetat P.H.,CEA Saclay Nuclear Research Center
Radioprotection | Year: 2013

During an accidental release of tritium, mechanisms of hydrogen transfer from air to man are very numerous, dependent on multiple climate, physiological and biological parameters, and the kinetic is highly variable from one environmental compartment to another. To evaluate the impact of an acute tritium release requires either an overall assessment of the state of the environment during the release and the following hours from a number of restricted data, or the establishment of a significant data bank, a complex model and a system of data acquisition in real time whose potential for daily purposes is very hypothetical. To facilitate the first approach, this paper discusses the key elements of the mechanisms to guide the choice of parameters for a rapid assessment of the situation, and to clarify the types of measurements to carry out and their interpretation. © 2013 EDP Sciences. Source


Nikolovski J.-P.,CEA Saclay Nuclear Research Center
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2013

This paper presents a passive (X, Y) giant tap screen panel (GTP). Based on the time difference of arrival principle (TDOA), the device localizes low-energy impacts of around 1 mJ generated by fingernail taps. Selective detection of A0 Lamb waves generated in the upper frequency spectrum, around 100 kHz, makes it possible to detect light to strong impacts with equal resolution or precision, close to 1 cm and 2 mm, respectively, for a 10-mm-thick and 1-m2 glass plate. Additionally, with glass, symmetrical beveling of the edges is used to create a tsunami effect that reduces the minimum impacting speed for light taps by a factor of three. Response time is less than 1 ms. Maximum panel size is of the order of 10 m2. A rugged integrated flat design with embedded transducers in an electrically shielding frame features waterproof and sticker/tag proof operation. Sophisticated electronics with floating amplification maintains the panel at its maximum possible sensitivity according to the surrounding noise. Amplification and filtering turns the panel into a microphone and loudspeaker featuring 50 mV/Pa as a microphone and up to 80 dBlin between 500 Hz and 8 kHz as a loudspeaker. © 1986-2012 IEEE. Source


Alvioli M.,European Center for Theoretical Studies in Nuclear Physics and Related Areas | Soyez G.,CEA Saclay Nuclear Research Center | Triantafyllopoulos D.N.,Fondazione Bruno Kessler
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

In processes involving small-x partons, like in deep inelastic scattering and in hadronic collisions at high energy, the final state can be expressed in terms of correlators of Wilson lines. We study such high-point correlators evolving according to the JIMWLK equation and we confirm the results of previous numerical and analytic work, by using an independent method, that the solution to the JIMWLK equation can be very well approximated by an appropriate Gaussian wave function. We explore both fixed and running coupling evolution, where in the latter the scale is set according to various prescriptions. As a byproduct, we also numerically confirm to high accuracy the validity of the law governing the behavior of the S-matrix close to the unitarity limit, the Levin-Tuchin formula. We furthermore outline how to calculate correlators with open color indices. © 2013 American Physical Society. Source


Aly J.-J.,CEA Saclay Nuclear Research Center
Astrophysical Journal | Year: 2012

We consider a particular class of three-dimensional magnetostatic equilibria in which the plasma is submitted to a vertical gravitational field and the gradient of the total (thermal+magnetic) pressure vanishes. We show analytically that an equilibrium in that class makes the energy an absolute minimum in the set of all the configurations accessible from it by an arbitrary finite deformation constrained by ideal MHD and imposed to vanish on a rigid conducting wall (line-tying condition). Along with energy conservation, this implies the nonlinear ideal stability of that equilibrium in the following sense. Suppose that a perturbation of energy w(0) is applied at time t = 0 and thus evolves by obeying the nonlinear MHD equations. Then some measure of the sizes of the plasma velocity and the deformation of the structure can be made to stay at any t ≥ 0 below an arbitrarily prescribed value by choosing w(0) small enough. Nonlinear stability also holds true for a configuration obtained by superposing an equilibrium of the previous type and a nonmagnetic equilibrium which is also an energy minimizer - for instance an equilibrium with uniform specific entropy, which is shown to have that property. Our result applies to a subset of a family of equilibria, computed by B. C. Low, which includes in particular the standard Kippenhahn-Schlüter model describing the magnetic support of solar corona prominences. © 2012. The American Astronomical Society. All rights reserved. Source


Bellazzini B.,CEA Saclay Nuclear Research Center | Bellazzini B.,University of Padua | Csaki C.,Cornell University | Serra J.,Cornell University
European Physical Journal C | Year: 2014

For the closing article in this volume on supersymmetry, we consider the alternative options to SUSY theories: we present an overview of composite Higgs models in light of the discovery of the Higgs boson. The small value of the physical Higgs mass suggests that the Higgs quartic is likely loop generated; thus models with tree-level quartics will generically be more tuned. We classify the various models (including bona fide composite Higgs, little Higgs, holographic composite Higgs, twin Higgs and dilatonic Higgs) based on their predictions for the Higgs potential, review the basic ingredients of each of them, and quantify the amount of tuning needed, which is not negligible in any model. We explain the main ideas for generating flavor structure and the main mechanisms for protecting against large flavor violating effects, and we present a summary of the various coset models that can result in realistic pseudo-Goldstone Higgses. We review the current experimental status of such models by discussing the electroweak precision, flavor, and direct search bounds, and we comment on the UV completions of such models and on ways to incorporate dark matter. © 2014 The Author(s). Source


Kokhanovsky A.A.,University of Bremen | Breon F.-M.,CEA Saclay Nuclear Research Center
IEEE Geoscience and Remote Sensing Letters | Year: 2012

We describe a two-parameter model for the reflectance of snow and test it against multispectral and multi-angular observations. The first parameter of the model is proportional to the effective snow grain size. The second parameter accounts for the impact of soot and other pollutants on snow absorption. The model is analytical and is easily inverted against a set of multispectral observations. To test the ability of the model to reproduce snow reflectance, we use a multispectral and multidirectional set of measurements acquired by the POLDER-3 instrument onboard the Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) satellite. We selected pure snow targets over Greenland and Antarctica. The model reproduces the main features of the snow angular reflectance: 1) the snow reflectance generally decreases toward longer wavelengths, 2) the reflectance has maximum in the forward scattering direction at large view zenith angles, and 3) the reflectance variations in the perpendicular plane are small compared to those observed in the principal plane. The coefficient of correlation between the results of simulations and the measurements exceeds 85% in most of cases. © 2012 IEEE. Source


Duplantier B.,CEA Saclay Nuclear Research Center | Sheffield S.,Massachusetts Institute of Technology
Physical Review Letters | Year: 2011

We show that when two boundary arcs of a Liouville quantum gravity random surface are conformally welded to each other (in a boundary length-preserving way) the resulting interface is a random curve called the Schramm-Loewner evolution. We also develop a theory of quantum fractal measures (consistent with the Knizhnik-Polyakov-Zamolochikov relation) and analyze their evolution under conformal welding maps related to Schramm-Loewner evolution. As an application, we construct quantum length and boundary intersection measures on the Schramm-Loewner evolution curve itself. © 2011 American Physical Society. Source


Kirilovsky D.,CEA Saclay Nuclear Research Center | Kirilovsky D.,French National Center for Scientific Research
Photosynthesis Research | Year: 2014

Photosynthetic organisms tightly regulate the energy arriving to the reaction centers in order to avoid photodamage or imbalance between the photosystems. To this purpose, cyanobacteria have developed mechanisms involving relatively rapid (seconds to minutes) changes in the photosynthetic apparatus. In this review, two of these processes will be described: orange carotenoid protein(OCP)-related photoprotection and state transitions which optimize energy distribution between the two photosystems. The photoactive OCP is a light intensity sensor and an energy dissipater. Photoactivation depends on light intensity and only the red-active OCP form, by interacting with phycobilisome cores, increases thermal energy dissipation at the level of the antenna. A second protein, the "fluorescence recovery protein", is needed to recover full antenna capacity under low light conditions. This protein accelerates OCP conversion to the inactive orange form and plays a role in dislodging the red OCP protein from the phycobilisome. The mechanism of state transitions is still controversial. Changes in the redox state of the plastoquinone pool induce movement of phycobilisomes and/or photosystems leading to redistribution of energy absorbed by phycobilisomes between PSII and PSI and/or to changes in excitation energy spillover between photosystems. The different steps going from the induction of redox changes to movement of phycobilisomes or photosystems remain to be elucidated. © 2014 Springer Science+Business Media Dordrecht. Source


Proville L.,CEA Saclay Nuclear Research Center
Annals of Physics | Year: 2010

The present work is essentially concerned with the development of statistical theory for the low temperature dislocation glide in concentrated solid solutions where atom-sized obstacles impede plastic flow. In connection with such a problem, we compute analytically the external force required to drag an elastic string along a discrete two-dimensional square lattice, where some obstacles have been randomly distributed. Some numerical simulations allow us to demonstrate the remarkable agreement between simulations and theory for an obstacle density ranging from 1% to 50% and for lattices with different aspect ratios. The theory proves efficient on the condition that the obstacle-chain interaction remains sufficiently weak compared to the string stiffness. © 2009 Elsevier Inc. All rights reserved. Source


Taruya A.,University of Tokyo | Nishimichi T.,University of Tokyo | Bernardeau F.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Using a full implementation of resummed perturbation theory (PT) from a multipoint propagator expansion, we put forward new theoretical predictions for the two-point statistics of matter fluctuations in redshift space. The predictions consistently include PT corrections up to the two-loop order and are based on an improved prescription of the redshift-space distortions that properly takes into account their non-Gaussian impact from a systematic low-k expansion. In contrast to the previous studies that partly used standard PT calculations, the present treatment is able to provide a consistent prediction for both power spectra and correlation functions. These results are compared with N-body simulations with which a very good agreement is found up to the quadrupole moment. However, the theoretical predictions for the hexadecapole moment of the power spectra are found to significantly depart from the numerical results at low redshift. We examine this issue and find it to be likely related to an improper modeling of the redshift-space distortions damping effects on which this moment shows large dependence. © 2013 American Physical Society. Source


Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research | Nishimichi T.,University of Tokyo | Taruya A.,University of Tokyo
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We present a new approach to computing the matter density power spectrum, from large linear scales to small, highly nonlinear scales. Instead of explicitly computing a partial series of high-order diagrams, as in perturbative resummation schemes, we embed the standard perturbation theory within a realistic nonlinear Lagrangian-space ansatz. We also point out that an "adhesion-like" regularization of the shell-crossing regime is more realistic than a "Zel'dovich-like" behavior, where particles freely escape to infinity. This provides a "cosmic web" power spectrum with good small-scale properties that provide a good matching with a halo model on mildly nonlinear scales. We obtain a good agreement with numerical simulations on large scales, better than 3% for k≤1h Mpc-1, and on small scales, better than 10% for k≤10h Mpc-1, at z≥0.35, which improves over previous methods. © 2013 American Physical Society. Source


Beuf G.,CEA Saclay Nuclear Research Center
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

A family of wave solutions to the full Einstein equations in AdS 5 geometry is derived. These background solutions give by duality the response of N = 4 SYM at strong coupling to an arbitrary distribution of fast moving external sources for the energy-momentum tensor operator. We discuss the similarities of these solutions with the Color Glass Condensate effective theory for QCD at high energy. © 2010 Elsevier B.V. All rights reserved. Source


Lee Y.-K.,CEA Saclay Nuclear Research Center
Fusion Engineering and Design | Year: 2011

Beryllium is an important material in fusion technology for multiplying neutrons in blankets. However, beryllium nuclear data are differently presented in modern nuclear data evaluations. Recent investigations with the TRIPOLI-4 Monte Carlo simulation of the tritium breeding ratio (TBR) demonstrated that beryllium reaction data are the main source of the calculation uncertainties between ENDF/B-VII.0 and JEFF-3.1. To clarify the calculation uncertainties from data libraries on beryllium, in this study TRIPOLI-4 calculations of the Karlsruhe Neutron Transmission (KANT) experiment have been performed by using ENDF/B-VII.0 and new JEFF-3.1.1 data libraries. The KANT Experiment on beryllium has been used to validate neutron transport codes and nuclear data libraries. An elaborated KANT experiment benchmark has been compiled and published in the NEA/SINBAD database and it has been used as reference in the present work. The neutron multiplication in bulk beryllium assemblies was considered with a central D-T neutron source. Neutron leakage spectra through the 5, 10, and 17 cm thick spherical beryllium shells were calculated and five-group partial leakage multiplications were reported and discussed. In general, improved C/E ratios on neutron leakage multiplications have been obtained. Both ENDF/B-VII.0 and JEFF-3.1.1 beryllium data libraries of TRIPOLI-4 are acceptable now for fusion neutronics calculations. © 2011 Elsevier B.V. All rights reserved. Source


Chirita P.,University of Craiova | Schlegel M.L.,CEA Saclay Nuclear Research Center
Chemical Geology | Year: 2013

The reaction of FeS with Fe(III)-bearing acidic solutions (Fe(III)BAS) was probed at 25°C and pH between 2 and 3. Initial dissolved Fe3+ ([Fe3+]init) was varied from 0.1mM to 1mM, and the length of the experiments was 240min. Except for the experiment at initial pH 2, total dissolved iron ([Fe]total) decreased immediately (within 1min) after contact of FeS and Fe(III). Afterwards, [Fe]total increased smoothly. A progressive increase in pH values and an Eh decrease within 240min of reaction time were also observed. The reaction order of FeS dissolution in Fe(III)BAS with respect to [H+] is estimated to 0.65 at initial pH 3.0, and increases up to 1.0 with decreasing initial pH, indicating that [H+] is an important parameter of FeS dissolution in Fe(III)BAS. In contrast, changes in [Fe3+]init have only a limited effect on the rate of FeS dissolution in Fe(III)BAS. Raman spectra of initial and reacted FeS samples reveal the accumulation of α-S8-like material on FeS surface. These results support a mechanism of FeS dissolution in Fe(III)BAS starting with the protonation of mineral surface and Fe3+ (aq) adsorption. Adsorbed protons subsequently accelerate Fe2+ release from FeS matrix into solution. The adsorbed Fe3+ may oxidize sulfur moieties and generate insoluble species, presumably polysulfide and elemental sulfur. The subsequent migration of Fe2+ into solution is controlled by the formed sulfur rich layer. © 2012 Elsevier B.V. Source


Giraud B.G.,CEA Saclay Nuclear Research Center
Journal of Physics G: Nuclear and Particle Physics | Year: 2010

This paper describes five questions of some interest for the density functional theory in nuclear physics. These are, respectively, (i) the need for concave functionals, (ii) the nature of the Kohn-Sham potential for the radial density theory, (iii) a proper implementation of a density functional for an 'intrinsic' rotational density, (iv) the possible existence of a potential driving the square root of the density and (v) the existence of many models where a density functional can be explicitly constructed. © 2010 IOP Publishing Ltd. Source


Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Nuclear Physics B | Year: 2010

In addition to the superconformal symmetry of the underlying Lagrangian, the scattering amplitudes in planar N = 4 super-Yang-Mills theory exhibit a new, dual superconformal symmetry. We address the question of how powerful these symmetries are to completely determine the scattering amplitudes. We use the example of the NMHV superamplitudes to show that the combined action of conventional and dual superconformal symmetries is not sufficient to fix all the freedom in the tree-level amplitudes. We argue that the additional information needed comes from the study of the analytic properties of the amplitudes. The requirement of absence of spurious singularities, together with the correct multi-particle singular behavior, determines the unique linear combination of superinvariants corresponding to the n-particle NMHV superamplitude. The same result can be obtained recursively, by relating the n- and (n - 1)-particle amplitudes in the singular collinear limit. We also formulate constraints on the loop corrections to the superamplitudes, following from the analytic behavior in the above limits. We then show that, at one-loop level, the holomorphic anomaly of the tree amplitudes leads to the breakdown of dual Poincaré supersymmetry (equivalent to ordinary special conformal supersymmetry) of the ratio of the NMHV and MHV superamplitudes, but this anomaly does not affect dual conformal symmetry. © 2010 Elsevier B.V. All rights reserved. Source


Moshe M.,Technion - Israel Institute of Technology | Zinn-Justin J.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2015

Abstract: Three dimensional, U(N) symmetric, field theory with fermion matter coupled to a topological Chern-Simons term, in the large N limit is analyzed in details. We determine the conditions for the existence of a massless conformal invariant ground state as well as the conditions for a massive phase. We analyze the phase structure and calculate gauge invariant corelators comparing them in several cases to existing results. In addition to the non-critical explicitly broken scale invariance massive case we consider also a massive ground state where the scale symmetry is spontaneously broken. We show that such a phase appears only in the presence of a marginal deformation that is introduced by adding a certain scalar auxiliary field and discuss the fermion-boson dual mapping. The ground state contains in this case a massless U(N) singlet bound state goldstone boson- the dilaton whose properties are determined. We employ here the temporal gauge which is at variance with respect to past calculations using the light-cone gauge and thus, a check (though limited) of gauge independence is at hand. The large N properties are determined by using a field integral formalism and the steepest descent method. The saddle point equations, which take here the form of integral equations for non-local fields, determine the mass gap and the dressed fermion propagator. Vertex functions are calculated at leading order in 1/N as exact solutions of integral equations. From the vertex functions, we infer gauge invariant two-point correlation functions for scalar operators and a current. Indications about the consistency of the method are obtained by verifying that gauge-invariant quantities have a natural O(3) covariant form. As a further verification, in several occasions, a few terms of the perturbative expansion are calculated and compared with the exact results in the appropriate order. © 2015, The Author(s). Source


Kavanagh B.J.,CEA Saclay Nuclear Research Center | Kavanagh B.J.,University of Nottingham
Journal of Cosmology and Astroparticle Physics | Year: 2015

Dark matter (DM) direct detection experiments which are directionally-sensitive may be the only method of probing the full velocity distribution function (VDF) of the Galactic DM halo. We present an angular basis for the DM VDF which can be used to parametrise the distribution in order to mitigate astrophysical uncertainties in future directional experiments and extract information about the DM halo. This basis consists of discretising the VDF in a series of angular bins, with the VDF being only a function of the DM speed v within each bin. In contrast to other methods, such as spherical harmonic expansions, the use of this basis allows us to guarantee that the resulting VDF is everywhere positive and therefore physical. We present a recipe for calculating the event rates corresponding to the discrete VDF for an arbitrary number of angular bins N and investigate the discretisation error which is introduced in this way. For smooth, Standard Halo Model-like distribution functions, only N=3 angular bins are required to achieve an accuracy of around 01-30% in the number of events in each bin. Shortly after confirmation of the DM origin of the signal with around 50 events, this accuracy should be sufficient to allow the discretised velocity distribution to be employed reliably. For more extreme VDFs (such as streams), the discretisation error is typically much larger, but can be improved with increasing N. This method paves the way towards an astrophysics-independent analysis framework for the directional detection of dark matter. Source


Poirier M.,CEA Saclay Nuclear Research Center
High Energy Density Physics | Year: 2015

Density effects in ionized matter require particular attention since they modify energies, wavefunctions and transition rates with respect to the isolated-ion situation. The approach chosen in this paper is based on the ion-sphere model involving a Thomas-Fermi-like description for free electrons, the bound electrons being described by a full quantum mechanical formalism. This permits to deal with plasmas out of thermal local equilibrium, assuming only a Maxwell distribution for free electrons. For H-like ions, such a theory provides simple and rather accurate analytical approximations for the potential created by free electrons. Emphasis is put on the plasma potential rather than on the electron density, since the energies and wavefunctions depend directly on this potential. Beyond the uniform electron gas model, temperature effects may be analyzed. In the case of H-like ions, this formalism provides analytical perturbative expressions for the energies, wavefunctions and transition rates. Explicit expressions are given in the case of maximum orbital quantum number, and compare satisfactorily with results from a direct integration of the radial Schrödinger equation. Some formulas for lower orbital quantum numbers are also proposed. © 2015 Elsevier B.V. Source


Blaizot J.-P.,CEA Saclay Nuclear Research Center | Wschebor N.,University of the Republic of Uruguay
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We argue that the choice of an appropriate, massive, renormalization scheme can greatly improve the apparent convergence of perturbation theory at finite temperature. This is illustrated by the calculation of the pressure of a scalar field theory with quartic interactions, at 2-loop order. The result, almost identical to that obtained with more sophisticated resummation techniques, shows a remarkable stability as the coupling constant grows, in sharp contrast with standard perturbation theory. © 2014 The Authors. Source


Duguet T.,CEA Saclay Nuclear Research Center | Duguet T.,Michigan State University
Journal of Physics G: Nuclear and Particle Physics | Year: 2015

We extend coupled-cluster (CC) theory performed on top of a Slater determinant breaking rotational symmetry to allow for the exact restoration of the angular momentum at any truncation order. The main objective relates to the description of near-degenerate finite quantum systems with an open-shell character. As such, the newly developed many-body formalism offers a wealth of potential applications and further extensions dedicated to the ab initio description of, e.g., doubly open-shell atomic nuclei and molecule dissociation. The formalism, which encompasses both single-reference CC theory and projected Hartree-Fock theory as particular cases, permits the computation of usual sets of connected diagrams while consistently incorporating static correlations through the highly non-perturbative restoration of rotational symmetry. Interestingly, the yrast spectroscopy of the system, i.e. the lowest energy associated with each angular momentum, is accessed within a single calculation. A key difficulty presently overcome relates to the necessity to handle generalized energy and norm kernels for which naturally terminating CC expansions could be eventually obtained. The present work focuses on SU(2) but can be extended to any (locally) compact Lie group and to discrete groups, such as most point groups. In particular, the formalism will be soon generalized to U(1) symmetry associated with particle number conservation. This is relevant to Bogoliubov CC theory that was recently applied to singly open-shell nuclei. © 2015 IOP Publishing Ltd. Source


Bobev N.,University of Southern California | Ruef C.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2010

We find new non-supersymmetric solutions of five-dimensional ungauged supergravity coupled to two vector multiplets. The solutions are regular, horizonless and have the same asymptotic charges as non-extremal charged black holes. An essential ingredient in our construction is a four-dimensional Euclidean base which is a solution to Einstein-Maxwell equations. We construct stationary solutions based on the Euclidean dyonic Reissner-Nordstr̈om black hole as well as a six-parameter family with a dyonic Kerr-Newman-NUT base. These solutions can be viewed as compactifications of elevendimensional supergravity on a six-torus and we discuss their brane interpretation. Source


Dasgupta M.,University of Manchester | Dreyer F.,CNRS Theoretical and High Energy Physics | Salam G.P.,CERN | Soyez G.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2015

Abstract: As hadron collider physics continues to push the boundaries of precision, it becomes increasingly important to have methods for predicting properties of jets across a broad range of jet radius values R, and in particular for small R. In this paper we resum all leading logarithmic terms, αs n lnnR2, in the limit of small R, for a wide variety of observables. These include the inclusive jet spectrum, jet vetoes for Higgs physics and jet substructure tools. Some of the quantities that we consider are relevant also for heavy-ion collisions. Furthermore, we examine and comment on the underlying order-by-order convergence of the perturbative series for different R values. Our results indicate that small-R effects can be substantial. Phenomenological studies will appear in a forthcoming companion paper. © 2015, The Author(s). Source


Korchemsky G.P.,CEA Saclay Nuclear Research Center | Sokatchev E.,University of Savoy
Nuclear Physics B | Year: 2010

We perform the twistor (half-Fourier) transform of all tree n-particle superamplitudes in N = 4 SYM and show that it has a transparent geometric interpretation. We find that the Nk MHV amplitude is supported on a set of 2 k + 1 intersecting lines in twistor space and demonstrate that the corresponding line moduli form a lightlike (2 k + 1)-gon in moduli space. This polygon is triangulated into two kinds of lightlike triangles lying in different planes. We formulate simple graphical rules for constructing the triangulated polygons, from which the analytic expressions of the Nk MHV amplitudes follow directly, both in twistor and in momentum space. We also discuss the ordinary and dual conformal properties and the cancellation of spurious singularities in twistor space. © 2009 Elsevier B.V. All rights reserved. Source


Kedziora D.J.,Australian National University | Simenel C.,Australian National University | Simenel C.,CEA Saclay Nuclear Research Center
Physical Review C - Nuclear Physics | Year: 2010

Based on time-dependent Hartree-Fock theory, a new inverse quasifission mechanism is proposed to produce neutron-rich transfermium nuclei in the collision of prolate deformed actinides. Calculations show that the collision of the tip of one nucleus with the side of the other results in a nucleon flux toward the latter. The roles of nucleon evaporation and impact parameter, as well as collision time, are discussed. © 2010 The American Physical Society. Source


Pequignot M.,CEA Saclay Nuclear Research Center
Nuclear and Particle Physics Proceedings | Year: 2015

The advances in neutrino physics achieved over the last decades allow us to apply it for nuclear reactor monitoring. The Nucifer experiment aims to demonstrate the possibility to follow the reactor activity with the neutrino rate. Since April 2012 it was deployed at 7 m away from the 57 MWth Osiris research reactor at CEA-Saclay. With a better light collection and energy resolution the Stereo experiment will take place at the end of 2015 at around 10 m from the ILL research reactor in order to test the 4th neutrino hypothesis. We report here the Nucifer detector performances and the Stereo detector characteristics. © 2015 Elsevier B.V. Source


Cong N.,Peking University | Wang T.,CEA Saclay Nuclear Research Center | Nan H.,Peking University | Ma Y.,Peking University | And 3 more authors.
Global Change Biology | Year: 2013

The change in spring phenology is recognized to exert a major influence on carbon balance dynamics in temperate ecosystems. Over the past several decades, several studies focused on shifts in spring phenology; however, large uncertainties still exist, and one understudied source could be the method implemented in retrieving satellite-derived spring phenology. To account for this potential uncertainty, we conducted a multimethod investigation to quantify changes in vegetation green-up date from 1982 to 2010 over temperate China, and to characterize climatic controls on spring phenology. Over temperate China, the five methods estimated that the vegetation green-up onset date advanced, on average, at a rate of 1.3 ± 0.6 days per decade (ranging from 0.4 to 1.9 days per decade) over the last 29 years. Moreover, the sign of the trends in vegetation green-up date derived from the five methods were broadly consistent spatially and for different vegetation types, but with large differences in the magnitude of the trend. The large intermethod variance was notably observed in arid and semiarid vegetation types. Our results also showed that change in vegetation green-up date is more closely correlated with temperature than with precipitation. However, the temperature sensitivity of spring vegetation green-up date became higher as precipitation increased, implying that precipitation is an important regulator of the response of vegetation spring phenology to change in temperature. This intricate linkage between spring phenology and precipitation must be taken into account in current phenological models which are mostly driven by temperature. © 2012 Blackwell Publishing Ltd. Source


Tamanini N.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

An interaction between dark matter and dark energy is usually introduced by a phenomenological modification of the matter conservation equations, while the Einstein equations are left unchanged. Starting from some general and fundamental considerations, in this work it is shown that a coupling in the dark sector is likely to introduce new terms also in the gravitational dynamics. Specifically in the cosmological background equations a bulk dissipative pressure, characterizing viscous effects and able to suppress structure formation at small scales, should appear from the dark coupling. At the level of the perturbations the analysis presented in this work reveals instead the difficulties in properly defining the dark sector interaction from a phenomenological perspective. © 2015 American Physical Society. Source


Kavanagh B.J.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

The framework of nonrelativistic effective field theory (NREFT) aims to generalize the standard analysis of direct detection experiments in terms of spin-dependent and spin-independent interactions. We show that a number of NREFT operators lead to distinctive new directional signatures, such as prominent ringlike features in the directional recoil rate, even for relatively low-mass weakly interacting massive particles. We discuss these signatures and how they could affect the interpretation of future results from directional detectors. We demonstrate that considering a range of possible operators introduces a factor of 2 uncertainty in the number of events required to confirm the median recoil direction of the signal. Furthermore, using directional detection, it is possible to distinguish the more general NREFT interactions from the standard spin-indenpendent/spin-dependent interactions at the 2σ level with O(100-500) events. In particular, we demonstrate that for certain NREFT operators directional sensitivity provides the only method of distinguishing them from these standard operators, highlighting the importance of directional detectors in probing the particle physics of dark matter. © 2015 American Physical Society. Source


Bercegol H.,CEA Saclay Nuclear Research Center | Lehoucq R.,University Paris Diderot
Physical Review Letters | Year: 2015

Zero-point quantum fluctuations of the electromagnetic vacuum create the widely known London-van der Waals attractive force between two atoms. Recently, there has been a revived interest in the interaction of rotating matter with the quantum vacuum. Here, we consider a rotating pair of atoms maintained by London-van der Waals forces and calculate the frictional torque they experience due to zero-point radiation. Using a semiclassical framework derived from the fluctuation dissipation theorem, we take into account the full electrostatic coupling between induced dipoles. Considering the case of zero temperature only, we find a braking torque proportional to the angular velocity and to the third power of the fine structure constant. Although very small compared to London-van der Waals attraction, the torque is strong enough to induce the formation of dimers in binary collisions. This new friction phenomenon at the atomic level should induce a paradigm change in the explanation of irreversibility. © 2015 American Physical Society. Source


Breon F.-M.,CEA Saclay Nuclear Research Center
Atmospheric Chemistry and Physics | Year: 2013

Spaceborne reflectance measurements from the POLDER instrument are used to study the specific directional signature close to the backscatter direction. The data analysis makes it possible to derive the extinction-to-backscatter ratio (EBR), which is related to the inverse of the scattering phase function for an angle of 180 and is needed for a quantitative interpretation of lidar observations (active measurements). In addition, the multidirectional measurements are used to quantify the scattering phase function variations close to backscatter, which also provide some indication of the aerosol particle size and shape. The spatial distributions of both parameters show consistent patterns that are consistent with the aerosol type distributions. Pollution aerosols have an EBR close to 70, desert dust values are on the order of 50 and EBR of marine aerosols is close to 25. The scattering phase function shows an increase with the scattering angle close to backscatter. The relative increase ∂lnP/∂γ is close to 0.01 for dust and pollution type aerosols and 0.06 for marine type aerosols. These values are consistent with those retrieved from Mie simulations. © Author(s) 2013. CC Attribution 3.0 License. Source


Thuery P.,CEA Saclay Nuclear Research Center
Crystal Growth and Design | Year: 2016

When reacted with undecane-1,11-dicarboxylic acid under solvo-hydrothermal conditions in the presence of Mn(II) cations and 1,10-phenanthroline, uranyl ions give two-dimensional honeycomb networks which assemble to form a 3-fold Borromean entanglement. This structure is closely related to that of the helicates previously obtained with the shorter dodecanedioic acid. Replacement of 1,10-phenanthroline by 2,2′-bipyridine leads to the formation of a neutral one-dimensional heterometallic polymer. © 2016 American Chemical Society. Source


Bohmer C.G.,University College London | Tamanini N.,CEA Saclay Nuclear Research Center | Wright M.,University College London
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We consider an original variational approach for building new models of quintessence interacting with dark or baryonic matter. The coupling is introduced at the Lagrangian level using a variational formulation for relativistic fluids, where the interacting term generally depends on both the dynamical degrees of freedom of the theory and their spacetime derivatives. After deriving the field equations from the action, we consider applications in the context of cosmology. Two simple models are studied using dynamical system techniques showing the interesting phenomenology arising in this framework. We find that these models contain dark energy dominated late-time attractors with early-time matter dominated epochs and also obtain a possible dynamical crossing of the phantom barrier. The formulation and results presented here complete and expand the analysis exposed in the first part of this work, where only algebraic couplings, without spacetime derivatives, were considered. © 2015 American Physical Society. Source


Peronaci F.,International School for Advanced Studies | Schiro M.,CEA Saclay Nuclear Research Center | Capone M.,International School for Advanced Studies
Physical Review Letters | Year: 2015

Motivated by recent ultrafast pump-probe experiments on high-temperature superconductors, we discuss the transient dynamics of a d-wave BCS model after a quantum quench of the interaction parameter. We find that the existence of gap nodes, with the associated nodal quasiparticles, introduces a decay channel which makes the dynamics much faster than in the conventional s-wave model. For every value of the quench parameter, the superconducting gap rapidly converges to a stationary value smaller than the one at equilibrium. Using a sudden approximation for the gap dynamics, we find an analytical expression for the reduction of spectral weight close to the nodes, which is in qualitative agreement with recent experiments. © 2015 American Physical Society. Source


Brax P.,CEA Saclay Nuclear Research Center | Davis A.-C.,University of Cambridge
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We investigate laboratory tests of dark energy theories which modify gravity in a way generalizing the inverse power law chameleon models. We make use of the tomographic description of such theories which captures f(R) models in the large curvature limit, the dilaton and the symmetron. We consider their effects in various experiments where the presence of a new scalar interaction may be uncovered. More precisely, we focus on the Casimir, Eötvös-Washington and neutron experiments. We show that dilatons, symmetrons and generalized chameleon models are efficiently testable in the laboratory. For generalized chameleons, we revise their status in the light of forthcoming Casimir experiments like CANNEX in Amsterdam and show that they are within reach of detection. © 2015 American Physical Society. Source


Gonzalez A.I.,CEA Saclay Nuclear Research Center | Mejia Y.,National University of Colombia
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2011

We propose to use a mask with a nonredundant array (NRA) of multiple apertures to measure spatial coherence in two dimensions. The spatial distribution of the apertures in the mask is made in such a way that we obtain a quasi-uniform sampling in the coherence domain. The spatial coherence is obtained by Fourier transform of the interferogram generated by the mask when it is illuminated by the light field under analysis. © 2011 Optical Society of America. Source


Lespinats S.,French National Solar Energy Institute | Aupetit M.,CEA Saclay Nuclear Research Center
Computer Graphics Forum | Year: 2011

Multidimensional scaling is a must-have tool for visual data miners, projecting multidimensional data onto a two-dimensional plane. However, what we see is not necessarily what we think about. In many cases, end-users do not take care of scaling the projection space with respect to the multidimensional space. Anyway, when using non-linear mappings, scaling is not even possible. Yet, without scaling geometrical structures which might appear do not make more sense than considering a random map. Without scaling, we shall not make inference from the display back to the multidimensional space. No clusters, no trends, no outliers, there is nothing to infer without first quantifying the mapping quality. Several methods to qualify mappings have been devised. Here, we propose CheckViz, a new method belonging to the framework of Verity Visualization. We define a two-dimensional perceptually uniform colour coding which allows visualizing tears and false neighbourhoods, the two elementary and complementary types of geometrical mapping distortions, straight onto the map at the location where they occur. As examples shall demonstrate, this visualization method is essential to help users make sense out of the mappings and to prevent them from over interpretations. It could be applied to check other mappings as well. © 2010 The Authors Computer Graphics Forum © 2010 The Eurographics Association and Blackwell Publishing Ltd. Source


Bianconi A.,University of Brescia | Tomasi-Gustafsson E.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2015

An intriguing and elusive feature of the timelike hadron form factor is the possible presence of an imaginary part associated to rescattering processes. We find evidence of that in the recent and precise data on the proton timelike form factor measured by the BABAR Collaboration. By plotting these data as a function of the 3-momentum of the relative motion of the final proton and antiproton, a systematic sinusoidal modulation is highlighted in the near-threshold region. Our analysis attributes this pattern to rescattering processes at a relative distance of 0.7-1.5 fm between the centers of the forming hadrons. This distance implies a large fraction of inelastic processes in p¯p interactions, and a large imaginary part in the related e+e-→p¯p reaction because of unitarity. © 2015 American Physical Society. Source


Moudden Y.,CEA Saclay Nuclear Research Center | Bobin J.,Stanford University
IEEE Transactions on Image Processing | Year: 2011

Generalized morphological component analysis (GMCA) is a recent algorithm for multichannel data analysis which was used successfully in a variety of applications including multichannel sparse decomposition, blind source separation (BSS), color image restoration and inpainting. Building on GMCA, the purpose of this contribution is to describe a new algorithm for BSS applications in hyperspectral data processing. It assumes the collected data is a mixture of components exhibiting sparse spectral signatures as well as sparse spatial morphologies, each in specified dictionaries of spectral and spatial waveforms. We report on numerical experiments with synthetic data and application to real observations which demonstrate the validity of the proposed method. © 2011 IEEE. Source


Zhao Y.,University of Bristol | Zhao Y.,CEA Saclay Nuclear Research Center | Harrison S.P.,University of Bristol | Harrison S.P.,Macquarie University
Climate Dynamics | Year: 2012

The response of monsoon circulation in the northern and southern hemisphere to 6 ka orbital forcing has been examined in 17 atmospheric general circulation models and 11 coupled ocean-atmosphere general circulation models. The atmospheric response to increased summer insolation at 6 ka in the northern subtropics strengthens the northern-hemisphere summer monsoons and leads to increased monsoonal precipitation in western North America, northern Africa and China; ocean feedbacks amplify this response and lead to further increase in monsoon precipitation in these three regions. The atmospheric response to reduced summer insolation at 6 ka in the southern subtropics weakens the southern-hemisphere summer monsoons and leads to decreased monsoonal precipitation in northern South America, southern Africa and northern Australia; ocean feedbacks weaken this response so that the decrease in rainfall is smaller than might otherwise be expected. The role of the ocean in monsoonal circulation in other regions is more complex. There is no discernable impact of orbital forcing in the monsoon region of North America in the atmosphere-only simulations but a strong increase in precipitation in the ocean-atmosphere simulations. In contrast, there is a strong atmospheric response to orbital forcing over northern India but ocean feedback reduces the strength of the change in the monsoon although it still remains stronger than today. Although there are differences in magnitude and exact location of regional precipitation changes from model to model, the same basic mechanisms are involved in the oceanic modulation of the response to orbital forcing and this gives rise to a robust ensemble response for each of the monsoon systems. Comparison of simulated and reconstructed changes in regional climate suggest that the coupled ocean-atmosphere simulations produce more realistic changes in the northern-hemisphere monsoons than atmosphere-only simulations, though they underestimate the observed changes in precipitation in all regions. Evaluation of the southern-hemisphere monsoons is limited by lack of quantitative reconstructions, but suggest that model skill in simulating these monsoons is limited. © 2011 The Author(s). Source


Roche A.,CEA Saclay Nuclear Research Center | Roche A.,ETH Zurich
IEEE Transactions on Medical Imaging | Year: 2011

Existing groupwise image registration algorithms for longitudinal data generally ignore continuous movements and signal changes that occur throughout image acquisition. We emphasize the case of functional magnetic resonance images, which present spatio-temporal distortion due to the combination of head motion during scanning and staggered slice acquisition. While there exist techniques to correct for motion and slice timing separately, a common dilemma is to determine which correction should be applied first. This paper proposes a four-dimensional realignment algorithm to perform both tasks simultaneously. Experiments conducted on simulated datasets with known movements suggest that the proposed algorithm provides more accurate image reconstruction than the classical two-step realignment procedure (temporal then spatial) as implemented, for instance, in the statistical parametric mapping software. © 2011 IEEE. Source


Scoccola N.N.,Comision Nacional de la Energia Atomica | Scoccola N.N.,CONICET | Scoccola N.N.,Favaloro University | Riska D.O.,Finnish Society of Science and Letters | Rho M.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Using the bound state version of the topological soliton model for the baryons we show that the existence of a bound (or quasibound) D¯-soliton state leads to the possibility of having hidden charm pentaquarks with quantum numbers and masses, which are compatible with those of the candidates recently reported by the LHCb experiment. The implications of heavy quark symmetry are elaborated. © 2015 American Physical Society. © 2015 American Physical Society. Source


Dijksman J.A.,Leiden University | Dijksman J.A.,Duke University | Wortel G.H.,Leiden University | Van Dellen L.T.H.,Leiden University | And 2 more authors.
Physical Review Letters | Year: 2011

We establish that the rheological curve of dry granular media is nonmonotonic, both in the presence and absence of external mechanical agitations. In the presence of weak vibrations, the nonmonotonic flow curves govern a hysteretic transition between slow but steady and fast, inertial flows. In the absence of vibrations, the nonmonotonic flow curve governs the yielding behavior of granular media. Finally, we show that nonmonotonic flow curves can be seen in at least two different flow geometries and for several granular materials. © 2011 American Physical Society. Source


Luzum M.,CEA Saclay Nuclear Research Center | Ollitrault J.-Y.,French National Center for Scientific Research
Physical Review Letters | Year: 2011

It was recently shown that fluctuations in the initial geometry of a heavy-ion collision generally result in a dipole asymmetry of the distribution of outgoing particles. This asymmetry, unlike the usual directed flow, is expected to be present at a wide range of rapidity-including midrapidity. The first evidence of this phenomenon can be seen in recent two-particle correlation data by the STAR Collaboration, providing the last element necessary to quantitatively describe long-range dihadron correlations. We extract differential directed flow from these data and propose a new direct measurement. © 2011 American Physical Society. Source


Chowdhury B.D.,University of Amsterdam | Puhm A.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Recently, Almheiri, Marolf, Polchinski, and Sully have suggested a Gedankenexperiment to test black hole complementarity. They claim that the postulates of black hole complementarity are mutually inconsistent and choose to give up the "absence of drama" for an infalling observer. According to them, the black hole is shielded by a firewall no later than Page time. This has generated some controversy. We find that an interesting picture emerges when we take into account objections from the advocates of fuzzballs. We reformulate Almheiri, Marolf, Polchinski, and Sully's Gedankenexperiment in the decoherence picture of quantum mechanics and find that low energy wave packets interact with the radiation quanta rather violently while high energy wave packets do not. This is consistent with Mathur's recent proposal of fuzzball complementarity for high energy quanta falling into fuzzballs. © 2013 American Physical Society. Source


Decelle A.,University Paris - Sud | Krzakala F.,CNRS Gulliver Laboratory | Moore C.,Santa Fe Institute | Zdeborova L.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2011

We present an asymptotically exact analysis of the problem of detecting communities in sparse random networks generated by stochastic block models. Using the cavity method of statistical physics and its relationship to belief propagation, we unveil a phase transition from a regime where we can infer the correct group assignments of the nodes to one where these groups are undetectable. Our approach yields an optimal inference algorithm for detecting modules, including both assortative and disassortative functional modules, assessing their significance, and learning the parameters of the underlying block model. Our algorithm is scalable and applicable to real-world networks, as long as they are well described by the block model. © 2011 American Physical Society. Source


Derosa M.L.,Lockheed Martin | Brun A.S.,CEA Saclay Nuclear Research Center | Hoeksema J.T.,Stanford University
Astrophysical Journal | Year: 2012

The variable magnetic field of the solar photosphere exhibits periodic reversals as a result of dynamo activity occurring within the solar interior. We decompose the surface field as observed by both the Wilcox Solar Observatory and the Michelson Doppler Imager into its harmonic constituents, and present the time evolution of the mode coefficients for the past three sunspot cycles. The interplay between the various modes is then interpreted from the perspective of general dynamo theory, where the coupling between the primary and secondary families of modes is found to correlate with large-scale polarity reversals for many examples of cyclic dynamos. Mean-field dynamos based on the solar parameter regime are then used to explore how such couplings may result in the various long-term trends in the surface magnetic field observed to occur in the solar case. © 2012 The American Astronomical Society. All rights reserved. Source


Simenel C.,Australian National University | Simenel C.,CEA Saclay Nuclear Research Center
Physical Review Letters | Year: 2011

The Balian-Vénéroni (BV) variational principle, which optimizes the evolution of the state according to the relevant observable, is used at the mean-field level to determine the particle-number fluctuations in fragments of many-body systems. For fermions, the numerical evaluation of such fluctuations requires the use of a time-dependent Hartree-Fock (TDHF) code. Proton, neutron, and total nucleon number fluctuations in fragments produced in collisions of two Ca40 are computed well above the fusion barrier. For deep-inelastic collisions, the fluctuations calculated from the BV variational principle are much larger than standard TDHF results, and closer to experimental fluctuations. Correlations between proton and neutron numbers are determined. These correlations are shown to be larger with exotic systems where charge equilibration occurs. © 2011 American Physical Society. Source


Pepin C.,CEA Saclay Nuclear Research Center | Pepin C.,Federal University of Rio Grande do Norte | Norman M.R.,Argonne National Laboratory | Burdin S.,University of Bordeaux 1 | Ferraz A.,Federal University of Rio Grande do Norte
Physical Review Letters | Year: 2011

We argue that near a Kondo breakdown critical point, a spin liquid with spatial modulations can form. Unlike its uniform counterpart, we find that this occurs via a second order phase transition. The amount of entropy quenched when ordering is of the same magnitude as for an antiferromagnet. Moreover, the two states are competitive, and at low temperatures are separated by a first order phase transition. The modulated spin liquid we find breaks Z4 symmetry, as recently seen in the hidden order phase of URu2Si 2. Based on this, we suggest that the modulated spin liquid is a viable candidate for this unique phase of matter. © 2011 American Physical Society. Source


Brax P.,CEA Saclay Nuclear Research Center | Pignol G.,Joseph Fourier University
Physical Review Letters | Year: 2011

We consider the potential detection of chameleons using bouncing ultracold neutrons. We show that the presence of a chameleon field over a planar plate would alter the energy levels of ultracold neutrons in the terrestrial gravitational field. When chameleons are strongly coupled to nuclear matter, β108, we find that the shift in energy levels would be detectable with the forthcoming GRANIT experiment, where a sensitivity of the order of 1% of a peV is expected. We also find that an extremely large coupling β1011 would lead to new bound states at a distance of order 2μm, which is already ruled out by previous Grenoble experiments. The resulting bound, β1011, is already 3 orders of magnitude better than the upper bound, β1014, from precision tests of atomic spectra. © 2011 American Physical Society. Source


Ferrand G.,University of Manitoba | Decourchelle A.,CEA Saclay Nuclear Research Center | Safi-Harb S.,University of Manitoba
Astrophysical Journal | Year: 2012

Supernova remnants (SNRs) are believed to be the major contributors to Galactic cosmic rays. The detection of non-thermal emission from SNRs demonstrates the presence of energetic particles, but direct signatures of protons and other ions remain elusive. If these particles receive a sizeable fraction of the explosion energy, the morphological and spectral evolution of the SNR must be modified. To assess this, we run three-dimensional hydrodynamic simulations of a remnant coupled with a nonlinear acceleration model. We obtain the time-dependent evolution of the shocked structure, impacted by the Rayleigh-Taylor hydrodynamic instabilities at the contact discontinuity and by the back-reaction of particles at the forward shock. We then compute the progressive temperature equilibration and non-equilibrium ionization state of the plasma, and its thermal emission in each cell. This allows us to produce the first realistic synthetic maps of the projected X-ray emission from the SNR. Plasma conditions (temperature and ionization age) can vary widely over the projected surface of the SNR, especially between the ejecta and the ambient medium owing to their different composition. This demonstrates the need for spatially resolved spectroscopy. We find that the integrated emission is reduced with particle back-reaction, with the effect being more significant for the highest photon energies. Therefore, different energy bands, corresponding to different emitting elements, probe different levels of the impact of particle acceleration. Our work provides a framework for the interpretation of SNR observations with current X-ray missions (Chandra, XMM-Newton, and Suzaku) and with upcoming X-ray missions (such as Astro-H). © 2012. The American Astronomical Society. All rights reserved. Source


Shahbazi C.S.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2015

Abstract: We show that M-theory admits a class of supersymmetric eight-dimensional compactification background solutions, equipped with an internal complex pure spinor, more general than the Calabi-Yau one. Building-up on this result, we obtain a a particular class of supersymmetric M-theory eight-dimensional non-geometric compactification backgrounds with external three-dimensional Minkowski space-time, proving that the global space of the non-geometric compactification is again a differentiable manifold, although with very different geometric and topological properties respect to the corresponding standard M-theory compactification background: it is a compact complex manifold admitting a Kähler covering with deck transformations acting by holomorphic homotheties with respect to the Kähler metric. We show that this class of non-geometric compactifications evade the Maldacena-Nuñez no-go theorem by means of a mechanism originally developed by Mario García-Fernández and the author for Heterotic Supergravity, and thus do not require lP-corrections to allow for a nontrivial warp factor or four-form flux. We obtain an explicit compactification background on a complex Hopf four-fold that solves all the equations of motion of the theory, including the warp factor equation of motion. We also show that this class of non-geometric compactifications are equipped with a holomorphic principal torus fibration over a projective Kähler base as well as a codimension-one foliation with nearly-parallel G2-leaves, making thus contact with the work of M. Babalic and C. Lazaroiu on the foliation structure of the most general M-theory supersymmetric compactifications. © 2015, The Author(s). Source


Rosabal J.A.,University of Buenos Aires | Rosabal J.A.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2015

Abstract: In this work we revisit the E8× ℝ+ generalised Lie derivative encoding the algebra of diffeomorphisms and gauge transformations of compactifications of M-theory on eight-dimensional manifolds, by extending certain features of the E7× ℝ+ one. Compared to its Ed× ℝ+, d ≤ 7 counterparts, a new term is needed for consistency. However, we find that no compensating parameters need to be introduced, but rather that the new term can be written in terms of the ordinary generalised gauge parameters by means of a connection. This implies that no further degrees of freedom, beyond those of the field content of the E8 group, are needed to have a well defined theory. We discuss the implications of the structure of the E8× ℝ+ generalised transformation on the construction of the d = 8 generalised geometry. Finally, we suggest how to lift the generalised Lie derivative to eleven dimensions. © 2015, The Author(s). Source


Collinucci A.,Solvay Group | Savelli R.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2015

Abstract: Bound states of 7-branes known as ‘T-branes’ have properties that defy usual geometric intuition. For instance, the gauge group of n coincident branes may not be U(n). More surprisingly, matter may show up at unexpected loci, such as points. By analyzing T-branes of perturbative type IIB string theory in the tachyon condensation picture we gain the following insights: in a large class of models, the tachyon can be diagonalized even though the worldvolume Higgs cannot. In those cases, we see the structure of these bound states more manifestly, thereby drastically simplifying analysis of gauge groups and spectra. Whenever the tachyon is not diagonalizable, matter localizes at unexpected loci, and we find that there is a lower-dimensional brane bound to the 7-brane. © 2015, The Author(s). Source


Carrasco J.J.M.,CEA Saclay Nuclear Research Center | Kallosh R.,Stanford University | Linde A.,Stanford University
Journal of High Energy Physics | Year: 2015

Abstract: We develop four-parameter supergravity models of inflation and dark energy, constrained so that δρρ$$ \frac{\delta \rho }{\rho } $$, ns and the cosmological constant Λ take their known observable values, but where the mass of gravitino m3/2 and the tensor-to-scalar ratio r are free parameters. We focus on generalized cosmological α-attractor models, with logarithmic Kähler potentials, a nilpotent goldstino and spontaneously broken supersymmetry at the de Sitter minimum. The future data on B-modes will specify the parameter α, measuring the geometry of the Kähler manifold. The string landscape idea for dark energy is supported in these models via an incomplete cancellation of the universal positive goldstino and negative gravitino contribution. The scale of SUSY breaking M related to the mass of gravitino in our models is a controllable parameter, independent on the scale of inflation, it will be constrained by LHC data and future collider Energy-frontier experiments. © 2015, The Author(s). Source


Satow D.,Kyoto University | Satow D.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We derive the generalized Boltzmann equation (GBE) near equilibrium from the Kadanoff-Baym equation for quark excitation with ultrasoft momentum (∼g2T, where g is the coupling constant and T is the temperature) in quantum chromodynamics at extremely high T, and show that the equation is equivalent to the self-consistent equation derived in the resummed perturbation scheme used to analyze the quark propagator. We obtain the expressions of the dispersion relation, the damping rate, and the strength of a quark excitation with ultrasoft momentum by solving the GBE. We also show that the GBE enables us to obtain the equation determining the n-point function containing a pair of quarks and (n-2) gluon external lines whose momenta are ultrasoft. © 2013 American Physical Society. Source


Giecold G.C.,CEA Saclay Nuclear Research Center
Journal of High Energy Physics | Year: 2010

The supergravity dual to N regular and M fractional D2-branes on a cone over CP3 has a naked singularity in the infrared. One can resolve this singularity and obtain a regular fractional D2-brane solution dual to a confining 2+1 dimensional N = 1 supersymmetric field theory. The confining vacuum of this theory is described by the solution of Cvetic, Gibbons, Lu and Pope [1]. In this paper, we explore the alternative possibility for resolving the singularity - the creation of a regular horizon. The black-hole solution we find corresponds to the deconfined phase of this dual gauge theory in three dimensions. This solution is derived in perturbation theory in the number of fractional branes. We argue that there is a first-order deconfinement transition. Connections to Chern-Simons matter theories, the ABJM proposal and fractional M2-branes are presented. © 2010 SISSA. Source


Iancua E.,CEA Saclay Nuclear Research Center | Muelleb A.H.,Columbia University
Journal of High Energy Physics | Year: 2010

We use the holographic dual of a finite-temperature, strongly-coupled, gauge theory with a small number of flavors of massive fundamental quarks to study meson excitations and deep inelastic scattering (DIS) in the low-temperature phase, where the mesons are stable. We show that a high-energy flavor current with nearly light-like kinematics disappears into the plasma by resonantly producing vector mesons in highly excited states. This mechanism generates the same DIS structure functions as in the high temperature phase, where mesons are unstable and the current disappears through medium-induced parton branching. To establish this picture, we derive analytic results for the meson spectrum, which are exact in the case of light-like mesons and which corroborate and complete previous, mostly numerical, studies in the literature. We find that the meson levels are very finely spaced near the light-cone, so that the current can always decay, without a fine-tuning of its kinematics. Source


Valageas P.,CEA Saclay Nuclear Research Center | Valageas P.,French National Center for Scientific Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We investigate the possible accuracy that can be reached by analytical models for the matter density power spectrum and correlation function. Using a realistic description of the power spectrum that combines perturbation theory with a halo model, we study the convergence rate of several perturbative expansion schemes and the impact of nonperturbative effects, as well as the sensitivity to phenomenological halo parameters. We check that the simple reorganization of the standard perturbative expansion, with a Gaussian damping prefactor, provides a well-ordered convergence and a finite correlation function that yields a percent accuracy at the baryon acoustic oscillation peak (as soon as one goes to second order). Lagrangian-space expansions are somewhat more efficient, when truncated at low orders, but may diverge at high orders. We find that whereas the uncertainty on the halo-profile mass-concentration relation is not a strong limitation, the uncertainty on the halo mass function can severely limit the accuracy of theoretical predictions for P(k) (this also applies to the power spectra measured in numerical simulations). The real-space correlation function provides a better separation between perturbative and nonperturbative effects, which are restricted to xa 10h-1 Mpc at all redshifts. © 2013 American Physical Society. Source


Raupach M.R.,CSIRO | Rayner P.J.,CEA Saclay Nuclear Research Center | Paget M.,CSIRO
Energy Policy | Year: 2010

We evaluate the joint use of satellite-observed intensity of urban nightlights and census-based population density data as constraints on the spatial structure of CO2 emissions from fossil fuels. Findings are: (1) the probability that population density exceeds a given value follows a power-law distribution over two orders of magnitude of population density, encompassing the 40% of the global population at the highest densities. (2) The corresponding probability distribution for nightlights intensity also follows a power-law, departing near instrumental saturation. (3) Assuming that the true nightlights intensity distribution follows the power-law above instrumental saturation, we obtain a correction for saturation errors in the nightlights data. The amplification of nightlights intensity required to correct for saturation errors is estimated to be a factor of 1.15-1.23 globally and much greater in regions with high nightlights intensities. (4) Correcting for saturation, we observe clear empirical relationships between nightlights intensity and areal densities of energy consumption, fossil-fuel emissions and economic activity, holding throughout the development spectrum. (5) We indicate how these relationships underpin a fossil-fuel data assimilation system (FFDAS) for estimating fossil-fuel CO2 emissions. © 2009. Source


Chalons C.,CEA Saclay Nuclear Research Center
Networks and Heterogeneous Media | Year: 2010

This paper is devoted to the study of the one dimensional interfacial coupling of two PDE systems at a given fixed interface, say x = 0. Each system is posed on a half-space, namely x < 0 and x > 0. As an interfacial model, a coupling condition whose objective is to enforce the continuity (in a weak sense) of a prescribed variable is generally imposed at x = 0. We first focus on the coupling of two scalar conservation laws and state an existence result for the coupled Riemann problem. Numerical experiments are also proposed. We then consider, both from a theoretical and a numerical point of view, the coupling of two-phase flow models namely a drift-flux model and a two-fluid model. In particular, the link between both models will be addressed using asymptotic expansions. © American Institute of Mathematical Sciences. Source


Marrakchi-Kacem L.,CEA Saclay Nuclear Research Center
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention | Year: 2010

The deep brain nuclei play an important role in many brain functions and particularly motor control. Damage to these structures result in movement disorders such as in Parkinson's disease or Huntington's disease, or behavioural disorders such as Tourette syndrome. In this paper, we propose to study the connectivity profile of the deep nuclei to the motor, associative or limbic areas and we introduce a novel tool to build a probabilistic atlas of these connections to the cortex directly on the surface of the cortical mantel, as it corresponds to the space of functional interest. The tool is then applied on two populations of healthy volunteers and patients suffering from severe Huntington's disease to produce two surface atlases of the connectivity of the basal ganglia to the cortical areas. Finally, robust statistics are used to characterize the differences of that connectivity between the two populations, providing new connectivity-based biomarkers of the pathology. Source


Roca P.,CEA Saclay Nuclear Research Center
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention | Year: 2010

This paper presents a connectivity-based parcellation of the human post-central gyrus, at the level of the group of subjects. The dimension of the clustering problem is reduced using a set of cortical regions of interest determined at the inter-subject level using a surface-based coordinate system, and representing the regions with a strong connection to the post-central gyrus. This process allows a clustering based on criteria which are more reproducible across subjects than in an intra-subject approach. We obtained parcels relatively stable in localisation across subjects as well as homogenous and well-separated to each other in terms of connectivity profiles. To address the parcellation at the inter-subject level provides a direct matching between parcels across subjects. In addition, this method allows the identification of subject-specific parcels. This property could be useful for the study of pathologies. Source