CNRS Laboratory for Nuclear and High-Energy Physics

Paris, France

CNRS Laboratory for Nuclear and High-Energy Physics

Paris, France
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Meiniel W.,French National Center for Scientific Research | Meiniel W.,Telecom ParisTech | Spinicelli P.,French National Center for Scientific Research | Angelini E.D.,Telecom ParisTech | And 6 more authors.
Proceedings - International Symposium on Biomedical Imaging | Year: 2017

In this work, we introduce an original strategy to apply the Compressed Sensing (CS) framework to a super-resolution Structured Illumination Microscopy (SIM) technique. We first define a framework for direct domain CS, that exploits the sparsity of fluorescence microscopy images in the Fourier domain. We then propose an application of this method to a fast 4-images SIM technique, which allows to reconstruct super-resolved fluorescence microscopy images using only 25% of the camera pixels for each acquisition. © 2017 IEEE.


Charles J.,Aix - Marseille University | Descotes-Genon S.,University Paris - Sud | Ocariz J.,CNRS Laboratory for Nuclear and High-Energy Physics | Ocariz J.,University Paris Diderot | Perez Perez A.,CNRS Hubert Curien Multi-disciplinary Institute
European Physical Journal C | Year: 2017

Dalitz-plot analyses of B→ Kππ decays provide direct access to decay amplitudes, and thereby weak and strong phases can be disentangled by resolving the interference patterns in phase space between intermediate resonant states. A phenomenological isospin analysis of B→ K∗(→ Kπ) π decay amplitudes is presented exploiting available amplitude analyses performed at the BaBar, Belle and LHCb experiments. A first application consists in constraining the CKM parameters thanks to an external hadronic input. A method, proposed some time ago by two different groups and relying on a bound on the electroweak penguin contribution, is shown to lack the desired robustness and accuracy, and we propose a more alluring alternative using a bound on the annihilation contribution. A second application consists in extracting information on hadronic amplitudes assuming the values of the CKM parameters from a global fit to quark flavour data. The current data yields several solutions, which do not fully support the hierarchy of hadronic amplitudes usually expected from theoretical arguments (colour suppression, suppression of electroweak penguins), as illustrated from computations within QCD factorisation. Some prospects concerning the impact of future measurements at LHCb and Belle II are also presented. Results are obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using the Rfit scheme to handle theoretical uncertainties. © 2017, The Author(s).


Joyce M.,CNRS Laboratory for Nuclear and High-Energy Physics | Morand J.,CNRS Laboratory for Nuclear and High-Energy Physics | Morand J.,National Institute for Theoretical Physics NITheP | Morand J.,Stellenbosch University | And 2 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2016

Isolated long-range interacting particle systems appear generically to relax to nonequilibrium states ("quasistationary states" or QSSs) which are stationary in the thermodynamic limit. A fundamental open question concerns the "robustness" of these states when the system is not isolated. In this paper we explore, using both analytical and numerical approaches to a paradigmatic one-dimensional model, the effect of a simple class of perturbations. We call them "internal local perturbations" in that the particle energies are perturbed at collisions in a way which depends only on the local properties. Our central finding is that the effect of the perturbations is to drive all the very different QSSs we consider towards a unique QSS. The latter is thus independent of the initial conditions of the system, but determined instead by both the long-range forces and the details of the perturbations applied. Thus in the presence of such a perturbation the long-range system evolves to a unique nonequilibrium stationary state, completely different from its state in absence of the perturbation, and it remains in this state when the perturbation is removed. We argue that this result may be generic for long-range interacting systems subject to perturbations which are dependent on the local properties (e.g., spatial density or velocity distribution) of the system itself. © 2016 American Physical Society.


Fraser M.,Queen's University of Belfast | Inserra C.,Queen's University of Belfast | Jerkstrand A.,Queen's University of Belfast | Kotak R.,Queen's University of Belfast | And 38 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present ultraviolet, optical and near-infrared observations of the interacting transient SN 2009ip, covering the period from the start of the outburst in 2012 October until the end of the 2012 observing season. The transient reached a peak magnitude of MV =-17.7mag, with a total integrated luminosity of 1.9 × 1049 erg over the period of 2012 August-December. The light curve fades rapidly, dropping by 4.5 mag from the V-band peak in 100 d. The optical and near-infrared spectra are dominated by narrow emission lines with broad electron scattering wings, signalling a dense circumstellar environment, together with multiple components of broad emission and absorption in H and He at velocities in the range 0.5-1.2 × 104 km s-1. We see no evidence for nucleosynthesized material in SN 2009ip, even in late-time pseudonebular spectra. We set a limit of<0.02Mȯ on themass of any possible synthesized 56Ni from the late-time light curve. A simple model for the narrow Balmer lines is presented and used to derive number densities for the circumstellar medium in the range ~109-1010cm. Our near-infrared data do not show any excess at longer wavelengths, and we see no other signs of dust formation. Our last data, taken in 2012 December, show that SN 2009ip has spectroscopically evolved to something quite similar to its appearance in late 2009, albeit with higher velocities. It is possible that neither of the eruptive and high-luminosity events of SN 2009ip were induced by a core collapse. We show that the peak and total integrated luminosity can be due to the efficient conversion of kinetic energy from colliding ejecta, and that around 0.05-0.1 Mȯ of material moving at 0.5-1 × 104 km s-1 could comfortably produce the observed luminosity. We discuss the possibility that these shells were ejected by the pulsational pair instability mechanism, in which case the progenitor star may still exist, and will be observed after the current outburst fades. The long-term monitoring of SN 2009ip, due to its proximity, has given the most extensive data set yet gathered of a high-luminosity interacting transient and its progenitor. It is possible that some purported Type IIn supernovae are in fact analogues of the 2012b event and that pre-explosion outbursts have gone undetected. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Labini F.S.,Centro Studi e Ricerche Enrico Fermi | Labini F.S.,CNR Institute for Complex Systems | Benhaiem D.,Centro Studi e Ricerche Enrico Fermi | Benhaiem D.,CNR Institute for Complex Systems | Joyce M.,CNRS Laboratory for Nuclear and High-Energy Physics
Monthly Notices of the Royal Astronomical Society | Year: 2015

Initially cold and spherically symmetric self-gravitating systems may give rise to a virial equilibrium state which is far from spherically symmetric, and typically triaxial. We focus here on how the degree of symmetry breaking in the final state depends on the initial density profile. We note that the most asymmetric structures result when, during the collapse phase, there is a strong injection of energy preferentially into the particles which are localized initially in the outer shells. These particles are still collapsing when the others, initially located in the inner part, are already re-expanding; the motion of particles in a time varying potential allow them to gain kinetic energy - in some cases enough to be ejected from the system. We show that this mechanism of energy gain amplifies the initial small deviations from perfect spherical symmetry due to finite N fluctuations. This amplification is more efficient when the initial density profile depends on radius, because particles have a greater spread of fall times compared to a uniform density profile, for which very close to symmetric final states are obtained. These effects lead to a distinctive correlation of the orientation of the final structure with the distribution of ejected mass, and also with the initial (very small) angular fluctuations. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Benetti S.,National institute for astrophysics | Nicholl M.,Queen's University of Belfast | Cappellaro E.,National institute for astrophysics | Pastorello A.,National institute for astrophysics | And 28 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We present optical photometry and spectra of the superluminous Type II/IIn supernova (SN) CSS121015:004244+132827 (z = 0.2868) spanning epochs from -30 d (rest frame) to more than 200 d after maximum. CSS121015 is one of the more luminous SNe ever found and one of the best observed. The photometric evolution is characterized by a relatively fast rise to maximum (~40 d in the SN rest frame), and by a linear post-maximum decline. The light curve shows no sign of a break to an exponential tail. A broad Hα is first detected at ~+40 d (rest frame). Narrow, barely resolved Balmer and [O iii] 5007 Å lines, with decreasing strength, are visible along the entire spectral evolution. The spectra are very similar to other superluminous supernovae (SLSNe) with hydrogen in their spectrum, and also to SN 2005gj, sometimes considered Type Ia interacting with H-rich circumstellar medium. The spectra are also similar to a subsample of H-deficient SLSNe. We propose that the properties of CSS121015 are consistent with the interaction of the ejecta with a massive, extended, opaque shell, lost by the progenitor decades before the final explosion, although a magnetar-powered model cannot be excluded. Based on the similarity of CSS121015 with other SLSNe (with and without H), we suggest that the shocked-shell scenario should be seriously considered as a plausible model for both types of SLSN. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Gabrielli A.,CNR Institute for Complex Systems | Gabrielli A.,University of Rome La Sapienza | Joyce M.,CNRS Laboratory for Nuclear and High-Energy Physics | Morand J.,CNRS Laboratory for Nuclear and High-Energy Physics
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

We explore the conditions on a pair interaction for the validity of the Vlasov equation to describe the dynamics of an interacting N-particle system in the large N limit. Using a coarse graining in phase space of the exact Klimontovich equation for the N-particle system, we evaluate, neglecting correlations of density fluctuations, the scalings with N of the terms describing the corrections to the Vlasov equation for the coarse-grained one-particle phase space density. Considering a generic interaction with radial pair force F(r), with F(r)∼1/rγ at large scales, and regulated to a bounded behavior below a "softening" scale, we find that there is an essential qualitative difference between the cases γd, i.e., depending on the the integrability at large distances of the pair force. In the former case, the corrections to the Vlasov dynamics for a given coarse-grained scale are essentially insensitive to the softening parameter , while for γ>d the amplitude of these terms is directly regulated by , and thus by the small scale properties of the interaction. This corresponds to a simple physical criterion for a basic distinction between long-range (γ≤d) and short-range (γ>d) interactions, different from the canonical one (γ≤d+1 or γ>d+1) based on thermodynamic analysis. This alternative classification, based on purely dynamical considerations, is relevant notably to understanding the conditions for the existence of so-called quasistationary states in long-range interacting systems. © 2014 American Physical Society.


Joyce M.,CNRS Laboratory for Nuclear and High-Energy Physics | Morand J.,CNRS Laboratory for Nuclear and High-Energy Physics | Sicard F.,University Paul Sabatier | Viot P.,CNRS Laboratory of Theoretical Physics and Condensed Matter
Physical Review Letters | Year: 2014

Hamiltonian systems with long-range interactions give rise to long-lived out-of-equilibrium macroscopic states, so-called quasistationary states. We show here that, in a suitably generalized form, this result remains valid for many such systems in the presence of dissipation. Using an appropriate mean-field kinetic description, we show that models with dissipation due to a viscous damping or due to inelastic collisions admit "scaling quasistationary states," i.e., states that are quasistationary in rescaled variables. A numerical study of one-dimensional self-gravitating systems confirms the relevance of these solutions and gives indications of their regime of validity in line with theoretical predictions. We underline that the velocity distributions never show any tendency to evolve towards a Maxwell-Boltzmann form. © 2014 American Physical Society.


PubMed | CNRS Laboratory for Nuclear and High-Energy Physics and CNRS Laboratory of Theoretical Physics and Condensed Matter
Type: Journal Article | Journal: Physical review. E | Year: 2016

Isolated long-range interacting particle systems appear generically to relax to nonequilibrium states (quasistationary states or QSSs) which are stationary in the thermodynamic limit. A fundamental open question concerns the robustness of these states when the system is not isolated. In this paper we explore, using both analytical and numerical approaches to a paradigmatic one-dimensional model, the effect of a simple class of perturbations. We call them internal local perturbations in that the particle energies are perturbed at collisions in a way which depends only on the local properties. Our central finding is that the effect of the perturbations is to drive all the very different QSSs we consider towards a unique QSS. The latter is thus independent of the initial conditions of the system, but determined instead by both the long-range forces and the details of the perturbations applied. Thus in the presence of such a perturbation the long-range system evolves to a unique nonequilibrium stationary state, completely different from its state in absence of the perturbation, and it remains in this state when the perturbation is removed. We argue that this result may be generic for long-range interacting systems subject to perturbations which are dependent on the local properties (e.g., spatial density or velocity distribution) of the system itself.


PubMed | CNRS Laboratory for Nuclear and High-Energy Physics, CNRS Laboratory of Theoretical Physics and Condensed Matter and CNRS Laboratory for Theoretical Physics
Type: Journal Article | Journal: Physical review letters | Year: 2014

Hamiltonian systems with long-range interactions give rise to long-lived out-of-equilibrium macroscopic states, so-called quasistationary states. We show here that, in a suitably generalized form, this result remains valid for many such systems in the presence of dissipation. Using an appropriate mean-field kinetic description, we show that models with dissipation due to a viscous damping or due to inelastic collisions admit scaling quasistationary states, i.e., states that are quasistationary in rescaled variables. A numerical study of one-dimensional self-gravitating systems confirms the relevance of these solutions and gives indications of their regime of validity in line with theoretical predictions. We underline that the velocity distributions never show any tendency to evolve towards a Maxwell-Boltzmann form.

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