Laboratoire Of Physique Theorique

Tlemcen, Algeria

Laboratoire Of Physique Theorique

Tlemcen, Algeria
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Parisi G.,University of Rome La Sapienza | Zamponi F.,Laboratoire Of Physique Theorique
Reviews of Modern Physics | Year: 2010

Hard spheres are ubiquitous in condensed matter: they have been used as models for liquids, crystals, colloidal systems, granular systems, and powders. Packings of hard spheres are of even wider interest as they are related to important problems in information theory, such as digitalization of signals, error correcting codes, and optimization problems. In three dimensions the densest packing of identical hard spheres has been proven to be the fcc lattice, and it is conjectured that the closest packing is ordered (a regular lattice, e.g., a crystal) in low enough dimension. Still, amorphous packings have attracted much interest because for polydisperse colloids and granular materials the crystalline state is not obtained in experiments for kinetic reasons. A theory of amorphous packings, and more generally glassy states, of hard spheres is reviewed here, that is based on the replica method: this theory gives predictions on the structure and thermodynamics of these states. In dimensions between two and six these predictions can be successfully compared with numerical simulations. The limit of large dimension is also discussed where an exact solution is possible. Some of the results presented here were published, but others are original: in particular, an improved discussion of the large dimension limit and new results on the correlation function and the contact force distribution in three dimensions. The main assumptions that are beyond the theory presented are clarified and, in particular, the relation between static computation and the dynamical procedures used to construct amorphous packings. There remain many weak points in the theory that should be better investigated. © 2010 The American Physical Society.

Prolhac S.,Laboratoire Of Physique Theorique | Prolhac S.,CNRS Laboratory for Theoretical Physics
Journal of Physics A: Mathematical and Theoretical | Year: 2015

The fluctuations of the current for the one-dimensional totally asymmetric exclusion process with L sites are studied in the relaxation regime of times T ∼ L3/2. Using Bethe ansatz for the periodic system with an evolution conditioned on special initial and final states, the Fourier transform of the probability distribution of the fluctuations is calculated exactly in the thermodynamic limit L → ∞ with finite density of particles. It is found to be equal to a sum over discrete realizations of a scalar field in a linear potential with coupling constant equal to the rescaled time T/L3/2. © 2015 IOP Publishing Ltd.

Schulgin W.,Solvay Group | Troost J.,Laboratoire Of Physique Theorique
Journal of High Energy Physics | Year: 2014

The quantum theory of a massless spin two particle is strongly constrained by diffeomorphism invariance, which is in turn implied by unitarity. We explicitly exhibit the space-time diffeomorphism algebra of string theory, realizing it in terms of world sheet vertex operators. Viewing diffeomorphisms as field redefinitions in the two-dimensional conformal field theory renders the calculation of their algebra straightforward. Next, we generalize the analysis to combinations of space-time anti-symmetric tensor gauge transformations and diffeomorphisms. We also point out a left-right split of the algebra combined with a twist that reproduces the C-bracket of double field theory. We further compare our derivation to an analysis in terms of marginal deformations as well as vertex operator algebras. © 2014 The Author(s).

Amatousse N.,Laboratoire Of Physique Theorique | Ait Abderrahmane H.,McGill University | Mehidi N.,Laboratoire Of Physique Theorique
International Journal of Engineering Science | Year: 2012

The weighted residual integral method is employed to investigate the flow of a thin layer of Walters-type B″ viscoelastic fluid flowing down an inclined plane. A simplified second-order two-equation model is derived; the model is analogous to the simplified model proposed by Ruyer-Quil and Manneville [Ruyer-Quil, C.; & Manneville, P. (2000). Improved modeling of flows down inclined planes. European Physical Journal B: Condensed Matter and Complex Systems, 15, 357-369] for Newtonian fluid. The normal mode analysis is used to investigate the linear stability of the Nusselt's flow and the correct critical condition for linear stability was found. The results of linear analysis indicate that the viscoelastic parameter, Γ, destabilizes the film flow as its magnitude increases. The two-equation model is used to investigate the particular case of traveling waves. The result is that the model exhibits bifurcation scenarios such heteroclinic, homoclinic, Hopf and period-doubling bifurcations. The influence of viscoelastic parameter on the nonlinear development of these traveling waves is discussed. © 2012 Elsevier Ltd. All rights reserved.

Plat X.,Laboratoire Of Physique Theorique | Capponi S.,Laboratoire Of Physique Theorique | Pujol P.,Laboratoire Of Physique Theorique
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

In this paper, we investigate the properties of frustrated three-leg spin-S tubes under a magnetic field. We concentrate on two kind of geometries for these tubes, one of which is relevant for the compound [(CuCl 2tachH)3Cl]Cl 2. We perform an analytical large-S path-integral approach to determine the phase diagrams, which exhibit several magnetization plateaux. Moreover, by combining the field-theory approach with a strong-coupling one, we also investigate the issue of gapless nonmagnetic excitations on some plateaux, dubbed chirality degrees of freedom for both tubes: on increasing the intertriangle exchange couplings, a gapless chiral phase transforms into a gapped "ferrochiral" state, possibly through intermediate "spin-imbalanced" states. All these predictions are confirmed numerically using large-scale density-matrix renormalization-group simulations for the S=3/2 case. © 2012 American Physical Society.

Gao X.,CNRS Astroparticle and Cosmology Lab | Gao X.,Laboratoire Of Physique Theorique | Gao X.,University Pierre and Marie Curie | Kobayashi T.,Kyoto University | And 2 more authors.
Physical Review Letters | Year: 2011

We completely clarify the feature of primordial non-Gaussianities of tensor perturbations in the most general single-field inflation model with second-order field equations. It is shown that the most general cubic action for the tensor perturbation hij is composed only of two contributions, one with two spacial derivatives and the other with one time derivative on each hij. The former is essentially identical to the cubic term that appears in Einstein gravity and predicts a squeezed shape, while the latter newly appears in the presence of the kinetic coupling to the Einstein tensor and predicts an equilateral shape. Thus, only two shapes appear in the graviton bispectrum of the most general single-field inflation model, which could open a new clue to the identification of inflationary gravitational waves in observations of cosmic microwave background anisotropies as well as direct detection experiments. © 2011 American Physical Society.

Deffayet C.,CNRS Astroparticle and Cosmology Lab | Gao X.,CNRS Astroparticle and Cosmology Lab | Gao X.,Laboratoire Of Physique Theorique | Gao X.,University Pierre and Marie Curie | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We determine the most general scalar field theories which have an action that depends on derivatives of order two or less, and have equations of motion that stay second order and lower on flat space-time. We show that those theories can all be obtained from linear combinations of Lagrangians made by multiplying a particular form of the Galileon Lagrangian by an arbitrary scalar function of the scalar field and its first derivatives. We also obtain curved space-time extensions of those theories which have second-order field equations for both the metric and the scalar field. This provides the most general extension, under the condition that field equations stay second order, of k-essence, Galileons, k-Mouflage as well as of the kinetically braided scalars. It also gives the most general action for a possible scalar classicalizer with second-order field equations. We discuss the relation between our construction and the Euler hierarchies of Fairlie et al. showing, in particular, that Euler hierarchies allow one to obtain the most general theory when the latter is shift symmetric. As a simple application of our formalism, we give the covariantized version of the conformal Galileon. © 2011 American Physical Society.

Huang M.-X.,University of Tokyo | Kashani-Poor A.-K.,Laboratoire Of Physique Theorique | Klemm A.,University of Bonn
Annales Henri Poincare | Year: 2013

We give an interpretation of the Ω deformed B-model that leads naturally to the generalized holomorphic anomaly equations. Direct integration of the latter calculates topological amplitudes of four-dimensional rigid N = 2 theories explicitly in general Ω-backgrounds in terms of modular forms. These amplitudes encode the refined BPS spectrum as well as new gravitational couplings in the effective action of N = 2 supersymmetric theories. The rigid N = 2 field theories we focus on are the conformal rank one N = 2 Seiberg-Witten theories. The failure of holomorphicity is milder in the conformal cases, but fixing the holomorphic ambiguity is only possible upon mass deformation. Our formalism applies irrespectively of whether a Lagrangian formulation exists. In the class of rigid N = 2 theories arising from compactifications on local Calabi-Yau manifolds, we consider the theory of local ℙ2. We calculate motivic Donaldson-Thomas invariants for this geometry and make predictions for generalized Gromov-Witten invariants at the orbifold point. © 2012 Springer Basel AG.

Loebbert F.,Niels Bohr Institute | Loebbert F.,Laboratoire Of Physique Theorique | Loebbert F.,Max Planck Institute For Gravitationsphysik
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

It is well known that integrable charges for short-range (e.g. nearest-neighbor) spin chains with periodic boundary conditions can be recursively generated by a so-called boost operator. In the past, this iterative construction has been generalized to periodic long-range spin chains as they appear in the context of the gauge/gravity correspondence. Here we introduce recursion relations for open long-range spin chain charges converting a short-range into a long-range integrable model. © 2012 American Physical Society.

Buric M.,University of Belgrade | Madore J.,Laboratoire Of Physique Theorique
The European Physical Journal C | Year: 2014

Two families of noncommutative extensions are given of a general space-time metric with spherical symmetry, both based on the matrix truncation of the functions on the sphere of symmetry. The first family uses the truncation to foliate space as an infinite set of spheres, and it is of dimension four and necessarily time-dependent; the second can be time-dependent or static, is of dimension five, and uses the truncation to foliate the internal space. © 2014 The Author(s).

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