Publications 2008
Publications de l'année 2008 :

A functional central limit theorem for interacting particle systems on transitive graphs
Paul Doukhan ^{1, 2}, Gabriel Lang ^{3}, Sana Louhichi ^{4}, Bernard Ycart ^{5, 6}
Markov Processes and Related Fields 14, 1 (2008) 79114
A finite range interacting particle system on a transitive graph is considered. Assuming that the dynamics and the initial measure are invariant, the normalized empirical distribution process converges in distribution to a centered diffusion process. As an application, a central limit theorem for certain hitting times, interpreted as failure times of a coherent system in reliability, is derived.
 1. Statistique Appliquée et MOdélisation Stochastique (SAMOS),
Université Paris I  Panthéon Sorbonne  2. Centre d'économie de la Sorbonne (CES),
CNRS : UMR8174 – Université Paris I  Panthéon Sorbonne  3. Mathématiques et Informatique Appliquées (MIA),
Institut national de la recherche agronomique (INRA) : UMR0518 – AgroParisTech  4. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  5. Mathématiques appliquées Paris 5 (MAP5),
CNRS : UMR8145 – Université Paris V  Paris Descartes  6. Laboratoire de Modélisation et Calcul (LMC  IMAG),
CNRS : UMR5523 – Université Joseph Fourier  Grenoble I – Institut National Polytechnique de Grenoble (INPG)
 1. Statistique Appliquée et MOdélisation Stochastique (SAMOS),

A Lattice Model for Colloidal Gels and Glasses
Florent Krzakala ^{1}, Marco Tarzia ^{2}, Lenka Zdeborová ^{3}
Physical Review Letters 101 (2008) 165702
We study a lattice model of attractive colloids. It is exactly solvable on sparse random graphs. As the pressure and temperature are varied it reproduces many characteristic phenomena of liquids, glasses and colloidal systems such as ideal gel formation, liquidglass phase coexistence, jamming, or the reentrance of the glass transition.
 1. CNRS ESPCI,
CNRS : UMR7083  2. Institut de Physique Théorique (ex SPhT) (IPHT),
CNRS : URA2306 – CEA : DSM/IPHT  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. CNRS ESPCI,

A note on limit shapes of minimal difference partitions
Alain Comtet ^{1, 2}, Satya N. Majumdar ^{1}, Sanjib Sabhapandit ^{1}
Journal of Mathematical Physics, Analysis, Geometry 4 (2008) 24
We provide a variational derivation of the limit shape of minimal difference partitions and discuss the link with exclusion statistics. Also see arXiv:0707.2312 for a related paper.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. IHP,
Institut Henri Poincaré
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Absolute limit for the capillary rise of a fluid
Treiner, J., Caupin, F., Cole, M.W., Balibar, S.
Europhysics Letters82 (2008) 56004

Adaptive networks of trading agents
Z. Burda ^{1}, A. Krzywicki ^{2}, O. C. Martin ^{3}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 78 (2008) 046106
Multiagent models have been used in many contexts to study generic collective behavior. Similarly, complex networks have become very popular because of the diversity of growth rules giving rise to scalefree behavior. Here we study adaptive networks where the agents trade ``wealth'' when they are linked together while links can appear and disappear according to the wealth of the corresponding agents; thus the agents influence the network dynamics and viceversa. Our framework generalizes a multiagent model of Bouchand and Mezard, and leads to a steady state with fluctuating connectivities. The system spontaneously selforganizes into a critical state where the wealth distribution has a fat tail and the network is scalefree; in addition, network heterogeneities lead to enhanced wealth condensation.
 1. Marian Smoluchowski Institute of Physics and Mark Kac Complex Systems Research Center,
Jagellonian University  2. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Marian Smoluchowski Institute of Physics and Mark Kac Complex Systems Research Center,

Behavior of Ising Spin Glasses in a Magnetic Field
Thomas Jorg ^{1}, Helmut G. Katzgraber ^{2}, Florent Krzakala ^{3}
Physical Review Letters 100 (2008) 197202
We study the existence of a spinglass phase in a field using Monte Carlo simulations performed along a nontrivial path in the fieldtemperature plane that must cross any putative de AlmeidaThouless instability line. The method is first tested on the Ising spin glass on a Bethe lattice where the instability line separating the spin glass from the paramagnetic state is also computed analytically. While the instability line is reproduced by our simulations on the meanfield Bethe lattice, no such instability line can be found numerically for the shortrange threedimensional model.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Theoretische Physik,
ETH Zurich  3. Laboratoire de PhysicoChimie Théorique (LPCT),
CNRS : UMR7083 – ESPCI ParisTech
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Berry phase in graphene : a semiclassical perspective
Carmier, P., Ullmo, D.
Physical Review B77 (2008) 245413

Bethe Ansatz in the Bernoulli Matching Model of Random Sequence Alignment
Satya N. Majumdar ^{1}, Kirone Mallick ^{2}, Sergei K. Nechaev ^{1}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 77 (2008) 011110
For the Bernoulli Matching model of sequence alignment problem we apply the Bethe ansatz technique via an exact mapping to the 5vertex model on a square lattice. Considering the terracelike representation of the sequence alignment problem, we reproduce by the Bethe ansatz the results for the averaged length of the Longest Common Subsequence in Bernoulli approximation. In addition, we compute the average number of nucleation centers of the terraces.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Service de Physique Théorique (SPhT),
CNRS : URA2306 – CEA : DSM/SPHT
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Breakdown of fluctuationdissipation relations in granular gases
J. J. Brey ^{1}, M. I. Garcia de Soria ^{2}, P. Maynar ^{1, 3}
Europhysics Letters (EPL) 84 (2008) 24002
A numerical molecular dynamics experiment measuring the twotime correlation function of the transversal velocity field in the homogeneous cooling state of a granular gas is reported. By measuring the decay rate and the amplitude of the correlations, the accuracy of the LandauLangevin equation of fluctuating hydrodynamics is checked. The results indicate that although a Langevin approach can be valid, the fluctuationdissipation relation must be modified, since the viscosity parameter appearing in it differs from the usual hydrodynamic shear viscosity.
 1. Fisica Teorica, Universidad de Sevilla,
Universidad de Sevilla  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud
 1. Fisica Teorica, Universidad de Sevilla,

Breaking of supersymmetry in onedimensional a random Hamiltonian
Hagendorf, C., Texier, C.
Journal of Physics A41 (2008) 405302

Brownian motion under annihilation dynamics
M. I. Garcia de Soria ^{1}, P. Maynar ^{2, 3}, E. Trizac ^{1}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 78 (2008) 061110
The behavior of a heavy tagged intruder immersed in a bath of particles evolving under ballistic annihilation dynamics is investigated. The FokkerPlanck equation for this system is derived and the peculiarities of the corresponding diffusive behavior are worked out. In the long time limit, the intruder velocity distribution function approaches a Gaussian form, but with a different temperature from its bath counterpart. As a consequence of the continuous decay of particles in the bath, the mean squared displacement increases exponentially in the collision per particle time scale. Analytical results are finally successfully tested against Monte Carlo numerical simulations.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud  3. Fisica Teorica, Universidad de Sevilla,
Universidad de Sevilla
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Casimir forces between arbitrary compact objects: Scalar and electromagnetic field
T. Emig ^{1, 2}, R. L. Jaffe ^{3}
Journal of Physics A General Physics 41 (2008) 164001
We develop an exact method for computing the Casimir energy between arbitrary compact objects, both with boundary conditions for a scalar field and dielectrics or perfect conductors for the electromagnetic field. The energy is obtained as an interaction between multipoles, generated by quantum source or current fluctuations. The objects' shape and composition enter only through their scattering matrices. The result is exact when all multipoles are included, and converges rapidly. A low frequency expansion yields the energy as a series in the ratio of the objects' size to their separation. As examples, we obtain this series for two spheres with Robin boundary conditions for a scalar field and dielectric spheres for the electromagnetic field. The full interaction at all separations is obtained for spheres with Robin boundary conditions and for perfectly conducting spheres.
 1. Institut für Theoretische Physik,
Universität zu Köln  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Center for Theoretical Physics, Laboratory for Nuclear Science and Department of Physics,
Aucune
 1. Institut für Theoretische Physik,

Casimir Forces between Compact Objects: I. The Scalar Case
T. Emig ^{1, 2}, N. Graham ^{3, 4}, R. L. Jaffe ^{4}, M. Kardar ^{5}
Physical Review D 77 (2008) 025005
We have developed an exact, general method to compute Casimir interactions between a finite number of compact objects of arbitrary shape and separation. Here, we present details of the method for a scalar field to illustrate our approach in its most simple form; the generalization to electromagnetic fields is outlined in Ref. [1]. The interaction between the objects is attributed to quantum fluctuations of source distributions on their surfaces, which we decompose in terms of multipoles. A functional integral over the effective action of multipoles gives the resulting interaction. Each object's shape and boundary conditions enter the effective action only through its scattering matrix. Their relative positions enter through universal translation matrices that depend only on field type and spatial dimension. The distinction of our method from the pairwise summation of twobody potentials is elucidated in terms of the scattering processes between three objects. To illustrate the power of the technique, we consider Robin boundary conditions $\phi \lambda \partial_n \phi=0$, which interpolate between Dirichlet and Neumann cases as $\lambda$ is varied. We obtain the interaction between two such spheres analytically in a large separation expansion, and numerically for all separations. The cases of unequal radii and unequal $\lambda$ are studied. We find sign changes in the force as a function of separation in certain ranges of $\lambda$ and see deviations from the proximity force approximation even at short separations, most notably for Neumann boundary conditions.
 1. Institut für Theoretische Physik,
Universität zu Köln  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Department of Physics,
Aucune  4. Center for Theoretical Physics, Laboratory for Nuclear Science and Department of Physics,
Aucune  5. Department of Physics Massachusetts Institute of Technology,
Massachusetts Institute of Technology
 1. Institut für Theoretische Physik,

Casimir forces between cylinders and plates
Sahand Jamal Rahi ^{1}, Thorsten Emig ^{2, 3}, Robert L. Jaffe ^{4}, Mehran Kardar ^{1}
Physical Review A: Atomic, Molecular and Optical Physics 78 (2008) 012104
We study collective interaction effects that result from the change of free quantum electrodynamic field fluctuations by one and twodimensional perfect metal structures. The Casimir interactions in geometries containing plates and cylinders is explicitly computed using partial wave expansions of constrained path integrals. We generalize previously obtained results and provide a more detailed description of the technical aspects of the approach \cite{Emig06}. We find that the interactions involving cylinders have a weak logarithmic dependence on the cylinder radius, reflecting that onedimensional perturbations are marginally relevant in 4D spacetime. For geometries containing two cylinders and one or two plates, we confirm a previously found nonmonotonic dependence of the interaction on the object's separations which does not follow from pairwise summation of twobody forces. Qualitatively, this effect is explained in terms of fluctuating charges and currents and their mirror images.
 1. Department of Physics,
Massachusetts Institute of Technology  2. Institut für Theoretische Physik,
Universität zu Köln  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  4. Center for Theoretical Physics and Laboratory for Nuclear Science,
Massachusetts Institute of Technology
 1. Department of Physics,

Circular dielectric cavity and its deformations
R. Dubertrand ^{1}, E. Bogomolny ^{1}, Nadia Djellali ^{2}, Mélanie Lebental ^{1, 2}, C. Schmit ^{1}
Physical Review A: Atomic, Molecular and Optical Physics 77 (2008) 013804
The construction of perturbation series for slightly deformed dielectric circular cavity is discussed in details. The obtained formulae are checked on the example of cut disks. A good agreement is found with direct numerical simulations and farfield experiments.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Laboratoire de Photonique Quantique et Moléculaire (LPQM),
CNRS : UMR8537 – École normale supérieure de Cachan  ENS Cachan
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Collective excitations of trapped onedimensional dipolar quantum gases
P. Pedri ^{1}, S. De Palo ^{2, 3}, Edmond Orignac ^{4}, R. Citro ^{5}, M. L. Chiofalo ^{6, 7}
Physical Review A: Atomic, Molecular and Optical Physics 77 (2008) 015601
We calculate the excitation modes of a 1D dipolar quantum gas confined in a harmonic trap with frequency $\omega_0$ and predict how the frequency of the breathing n=2 mode characterizes the interaction strength evolving from the TonksGirardeau value $\omega_2=2\omega_0$ to the quasiordered, superstrongly interacting value $\omega_2=\sqrt{5}\omega_0$. Our predictions are obtained within a hydrodynamic LuttingerLiquid theory after applying the Local Density Approximation to the equation of state for the homogeneous dipolar gas, which are in turn determined from Reptation Quantum Monte Carlo simulations. They are shown to be in quite accurate agreement with the results of a sumrule approach. These effects can be observed in current experiments, revealing the Luttingerliquid nature of 1D dipolar Bose gases.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Dipartimento di Fisica Teorica,
INFN – Università degli studi di Trieste  3. DEMOCRITOS,
Consiglio Nazionale delle Ricerche  4. Laboratoire de Physique de l'ENS Lyon (PhysENS),
CNRS : UMR5672 – École Normale Supérieure  Lyon  5. Dipartimento di Fisica "E. R. Caianiello" and CNISM,
Università degli studi di Salerno  6. INFN Dipartimento di Matematica,,
Università di Pisa  7. Centre Emile Borel,
Institut Henri Poincaré
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Collisional properties of weakly bound heteronuclear dimers
B. Marcelis ^{1, 2}, S. J. J. M. F. Kokkelmans ^{1}, G. V. Shlyapnikov ^{2, 3}, D. S. Petrov ^{2, 4}
Physical Review A: Atomic, Molecular and Optical Physics 77 (2008) 032707
We consider collisional properties of weakly bound heteronuclear molecules (dimers) formed in a twospecies mixture of atoms with a large mass difference. We focus on dimers containing light fermionic atoms as they manifest collisional stability due to an effective dimerdimer repulsion originating from the exchange of the light atoms. In order to solve the dimerdimer scattering problem we develop a theoretical approach, which provides a physically transparent and quantitative description of this fouratom system in terms of three and twobody observables. We calculate the elastic scattering amplitude and the rates of inelastic processes such as the trimer formation and the relaxation of dimers into deeply bound molecular states. Irrespective of whether the heavy atoms are bosons or fermions, the inelastic rate can be significantly lower than the rate of elastic collisions. Moreover, the measurement of the inelastic rate which is a fourbody observable, can be an efficient and precise tool for determining threebody observables such as the threebody parameter, positions of Efimov states and their lifetimes.
 1. Eindhoven University of Technology (TUE),
Eindhoven University of Technology  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Van der WaalsZeeman Institute,
University of Amsterdam  4. National Research Centre "Kurchatov Institute" (NRC KI),
University of Moscow
 1. Eindhoven University of Technology (TUE),

Collisional statistics of the hardsphere gas
P. Visco ^{1, 2}, F. van Wijland ^{1, 3}, E. Trizac ^{2}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 77 (2008) 041117
We investigate the probability distribution function of the free flight time and of the number of collisions in a hard sphere gas at equilibrium. At variance with naive expectation, the latter quantity does not follow Poissonian statistics, even in the dilute limit which is the focus of the present analysis. The corresponding deviations are addressed both numerically and analytically. In writing an equation for the generating function of the cumulants of the number of collisions, we came across a perfect mapping between our problem and a previously introduced model: the probabilistic ballistic annihilation process [Coppex et al., Phys. Rev. E 69 11303 (2004)]. We exploit this analogy to construct a MonteCarlo like algorithm able to investigate the asymptotically large time behavior of the collisional statistics within a reasonable computational time. In addition, our predictions are confronted against the results of Molecular Dynamics simulations and Direct Simulation Monte Carlo technique. An excellent agreement is reported.
 1. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Matière et Systèmes Complexes (MSC),
CNRS : UMR7057 – Université Paris VII  Paris Diderot
 1. Laboratoire de Physique Théorique d'Orsay (LPT),

Combinatorial aspects of boundary loop models
Jacobsen, J., Saleur, H.
Journal of Statistical Mechanics(2008) P01021

Comment on ‘Ultrametricity in the EdwardsAnderson Model’
Thomas Jorg ^{1}, Florent Krzakala ^{2}
Physical Review Letters 100 (2008) 159701
In a recent interesting Letter Contucci {\it et al.} have investigated several properties of the threedimensional (3d) EdwardsAnderson (EA) Ising spin glass. They claim to have found strong numerical evidence for the presence of a complex ultrametric structure similar to the one described by the replica symmetry breaking solution of the mean field model. We illustrate by numerical simulations that the relations used by Contucci {\it et al.} as evidence for an ultrametric structure in the 3d EA model are fulfilled to similar accuracy in the twodimensional EA model, which is welldescribed by the droplet picture and has no spin glass phase at finite temperature. We conclude that the data presented in the Contucci {\it et al.} Letter is not sufficient to dismiss the possibility that, e.g., the droplet model might describe the behavior of the 3d EA model.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Laboratoire de PhysicoChimie Théorique (LPCT),
CNRS : UMR7083 – ESPCI ParisTech
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Condensation and Extreme Value Statistics
Martin R. Evans ^{1}, Satya N. Majumdar ^{2}
Journal of Statistical Mechanics (2008) 05004
We study the factorised steady state of a general class of mass transport models in which mass, a conserved quantity, is transferred stochastically between sites. Condensation in such models is exhibited when above a critical mass density the marginal distribution for the mass at a single site develops a bump, $p_{\rm cond}(m)$, at large mass $m$. This bump corresponds to a condensate site carrying a finite fraction of the mass in the system. Here, we study the condensation transition from a different aspect, that of extreme value statistics. We consider the cumulative distribution of the largest mass in the system and compute its asymptotic behaviour. We show 3 distinct behaviours: at subcritical densities the distribution is Gumbel; at the critical density the distribution is Fréchet, and above the critical density a different distribution emerges. We relate $p_{\rm cond}(m)$ to the probability density of the largest mass in the system.
 1. SUPA, School of Physics, University of Edinburgh,
SUPA  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. SUPA, School of Physics, University of Edinburgh,

Constraint satisfaction problems with isolated solutions are hard
Lenka Zdeborová ^{1, 2}, Marc Mézard ^{1}
Journal of Statistical Mechanics: Theory and Experiment (2008) 12004
We study the phase diagram and the algorithmic hardness of the random `locked' constraint satisfaction problems, and compare them to the commonly studied 'nonlocked' problems like satisfiability of boolean formulas or graph coloring. The special property of the locked problems is that clusters of solutions are isolated points. This simplifies significantly the determination of the phase diagram, which makes the locked problems particularly appealing from the mathematical point of view. On the other hand we show empirically that the clustered phase of these problems is extremely hard from the algorithmic point of view: the best known algorithms all fail to find solutions. Our results suggest that the easy/hard transition (for currently known algorithms) in the locked problems coincides with the clustering transition. These should thus be regarded as new benchmarks of really hard constraint satisfaction problems.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Theorical Division (LANL),
Los Alamos National Laboratory,
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Critical points in coupled Potts models and critical phases in coupled loop models
Fendley, P., Jacobsen, J.L.
Journal of Physics A41 (2008) 215001

Critical Temperature Curve in the BECBCS Crossover
Evgeni Burovski ^{1}, Evgeny Kozik ^{2}, Nikolay Prokof'Ev ^{3, 4, 5}, Boris Svistunov ^{3, 4}, Matthias Troyer ^{6}
Physical Review Letters 101 (2008) 090402
The stronglycorrelated regime of the BCSBEC crossover can be realized by diluting a system of twocomponent fermions with a shortrange attractive interaction. We investigate this system via a novel continuousspacetime diagrammatic determinant Monte Carlo method and determine the universal curve $T_c/\epsilon_F$ for the transition temperature between the normal and the superfluid states as a function of the scattering length with the maximum on the BEC side. At unitarity, we confirm that $T_c/\epsilon_F = 0.152(7)$.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Department of Physics,
Department of Physics University of Massachussetts  3. Department of Physics,
University of Massachussetts  4. National Research Centre "Kurchatov Institute" (NRC KI),
University of Moscow  5. Theoretische Physik, EHT,
Theoretische Physik, EHT  6. Institut für Theoretische Physik,
ETH Zurich
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Crowding at the Front of the Marathon Packs
Sanjib Sabhapandit ^{1}, Satya N. Majumdar ^{1}, S. Redner ^{2}
Journal of statistical mechanicstheory and experiment (2008) L03001
We study the crowding of nearextreme events in the time gaps between successive finishers in major international marathons. Naively, one might expect these gaps to become progressively larger for betterplacing finishers. While such an increase does indeed occur from the middle of the finishing pack down to approximately 20th place, the gaps saturate for the first 1020 finishers. We give a probabilistic account of this feature. However, the data suggests that the gaps have a weak maximum around the 10th place, a feature that seems to have a sociological origin.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Center for Polymer Studies (CPS),
Boston University
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Deformations of the TracyWidom distribution
O. Bohigas ^{1}, J. X. de Carvalho ^{2, 3}, M. P. Pato ^{1, 2}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 79 (2008) 031117
In random matrix theory (RMT), the TracyWidom (TW) distribution describes the behavior of the largest eigenvalue. We consider here two models in which TW undergoes transformations. In the first one disorder is introduced in the Gaussian ensembles by superimposing an external source of randomness. A competition between TW and a normal (Gaussian) distribution results, depending on the spreading of the disorder. The second model consists in removing at random a fraction of (correlated) eigenvalues of a random matrix. The usual formalism of Fredholm determinants extends naturally. A continuous transition from TW to the Weilbull distribution, characteristc of extreme values of an uncorrelated sequence, is obtained.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Instituto de Fisica,
Universidade de São Paulo  3. MaxPlanckInstitut für Physik komplexer Systeme,
MaxPlanckInstitut
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Dipole Oscillations of a BoseEinstein Condensate in Presence of Defects and Disorder
M. Albert ^{1}, T. Paul ^{1}, N. Pavloff ^{1}, P. Leboeuf ^{1}
Physical Review Letters 100 (2008) 250405
We consider dipole oscillations of a trapped dilute BoseEinstein condensate in the presence of a scattering potential consisting either in a localized defect or in an extended disordered potential. In both cases the breaking of superfluidity and the damping of the oscillations are shown to be related to the appearance of a nonlinear dissipative flow. At supersonic velocities the flow becomes asymptotically dissipationless.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Disordered ensembles of random matrices
O. Bohigas ^{1}, J. X. de Carvalho ^{2, 3}, M. P. Pato ^{1, 2}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 77 (2008) 011122
It is shown that the families of generalized matrix ensembles recently considered which give rise to an orthogonal invariant stable L\'{e}vy ensemble can be generated by the simple procedure of dividing Gaussian matrices by a random variable. The nonergodicity of this kind of disordered ensembles is investigated. It is shown that the same procedure applied to random graphs gives rise to a family that interpolates between the Erd\'{o}sRenyi and the scale free models.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Instituto de Fisica,
Universidade de São Paulo  3. MaxPlanckInstitut für Physik komplexer Systeme,
MaxPlanckInstitut
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Distance matrices and isometric embeddings
E. Bogomolny ^{1}, O. Bohigas ^{1}, C. Schmit ^{1}
Journal of Mathematical Physics, Analysis, Geometry 4 (2008) 7
We review the relations between distance matrices and isometric embeddings and give simple proofs that distance matrices defined on euclidean and spherical spaces have all eigenvalues except one nonnegative. Several generalizations are discussed.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Distributions of Conductance and Shot Noise and Associated Phase Transitions
Pierpaolo Vivo ^{1}, Satya N. Majumdar ^{2}, Oriol Bohigas ^{2}
Physical Review Letters 101 (2008) 216809
For a chaotic cavity with two indentical leads each supporting N channels, we compute analytically, for large N, the full distribution of the conductance and the shot noise power and show that in both cases there is a central Gaussian region flanked on both sides by nonGaussian tails. The distribution is weakly singular at the junction of Gaussian and nonGaussian regimes, a direct consequence of two phase transitions in an associated Coulomb gas problem.
 1. The Abdus Salam International Centre for Theoretical Physics,
ICTP Trieste  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. The Abdus Salam International Centre for Theoretical Physics,

Dynamics of Annihilation I : Linearized Boltzmann Equation and Hydrodynamics
M. I. Garcia de Soria ^{1}, P. Maynar ^{2, 3}, G. Schehr ^{2}, A. Barrat ^{2}, E. Trizac ^{1}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 77 (2008) 051127
We study the nonequilibrium statistical mechanics of a system of freely moving particles, in which binary encounters lead either to an elastic collision or to the disappearance of the pair. Such a system of {\em ballistic annihilation} therefore constantly looses particles. The dynamics of perturbations around the free decay regime is investigated from the spectral properties of the linearized Boltzmann operator, that characterize linear excitations on all time scales. The linearized Boltzmann equation is solved in the hydrodynamic limit by a projection technique, which yields the evolution equations for the relevant coarsegrained fields and expressions for the transport coefficients. We finally present the results of Molecular Dynamics simulations that validate the theoretical predictions.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud  3. Fisica Teorica, Universidad de Sevilla,
Universidad de Sevilla
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Dynamics of Annihilation II: Fluctuations of Global Quantities
P. Maynar ^{1, 2}, M. I. Garcia de Soria ^{3}, G. Schehr ^{1}, A. Barrat ^{1}, E. Trizac ^{3}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 77 (2008) 051128
We develop a theory for fluctuations and correlations in a gas evolving under ballistic annihilation dynamics. Starting from the hierarchy of equations governing the evolution of microscopic densities in phase space, we subsequently restrict to a regime of spatial homogeneity, and obtain explicit predictions for the fluctuations and time correlation of the total number of particles, total linear momentum and total kinetic energy. Crosscorrelations between these quantities are worked out as well. These predictions are successfully tested against Molecular Dynamics and MonteCarlo simulations. This provides strong support for the theoretical approach developed, including the hydrodynamic treatment of the spectrum of the linearized Boltzmann operator. This article is a companion paper to arXiv:0801.2299 and makes use of the spectral analysis reported there.
 1. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud  2. Fisica Teorica, Universidad de Sevilla,
Universidad de Sevilla  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique d'Orsay (LPT),

Entropic effects in the verylowtemperature regime of diluted Ising spin glasses with discrete couplings
Thomas Jorg ^{1}, Federico RicciTersenghi ^{2, 3}
Physical Review Letters 100 (2008) 177203
We study linkdiluted $\pm J$ Ising spin glass models on the hierarchical lattice and on a threedimensional lattice close to the percolation threshold. We show that previously computed zero temperature fixed points are unstable with respect to temperature perturbations and do not belong to any critical line in the dilutiontemperature plane. We discuss implications of the presence of such spurious unstable fixed points on the use of optimization algorithms, and we show how entropic effects should be taken into account to obtain the right physical behavior and critical points.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Dipartimento di Fisica and INFM,
Università degli studi di Roma I  La Sapienza  3. International Centre for Theoretical Physics (ICTP),
the Abdus Salam International Centre for Theoretical Physics
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Equation of state and effective mass of the unitary Fermi gas in a 1D periodic potential
Gentaro Watanabe ^{1, 2}, Giuliano Orso ^{3}, Franco Dalfovo ^{4}, Lev P. Pitaevskii ^{5, 6}, Sandro Stringari ^{7}
Physical Review A: Atomic, Molecular and Optical Physics 78 (2008) 063619
By solving the Bogoliubov  de Gennes equations at zero temperature, we study the effects of a onedimensional optical lattice on the behavior of a superfluid Fermi gas at unitarity. We show that, due to the lattice, at low densities the gas becomes highly compressible and the effective mass is large, with a consequent significant reduction of the sound velocity. We discuss the role played by the lattice in the formation of molecules and the emergence of twodimensional effects in the equation of state. Predictions for the density profiles and for the frequency of the collective oscillations in the presence of harmonic trapping are also given.
 1. CNR INFMBEC and Departement of physics,
University of Trento  2. RIKEN The Insititute of Chemical and Physical Research,
RIKEN the insititute of chemical and physical research  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  4. CNR INFM BEC and Departement of physics,
University of Trento  5. Kapitza Institute for Physical Problems,
Kapitza Institute for Physical Problems  6. CNR INFM BEC and Departement of Physics,
University of Trento  7. CNRINFM BEC Center,
Universita di Trento
 1. CNR INFMBEC and Departement of physics,

Equation of state for hard sphere fluids with and without Kac tails
E. Trizac ^{1}, I. Pagonabarraga ^{2}
American Journal of Physics 76 (2008) 777
In this note, we propose a simple derivation of the one dimensional hard rod equation of state, with and without a Kac tail (appended long range and weak potential). The case of hard spheres in higher dimension is also addressed and it is shown there that our arguments which avoid any mathematical complication allow to recover the virial form of the equation of state in a direct way.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Departament de Física Fonamental, Universitat de Barcelona,
Departament de Física Fonamental, Universitat de Barcelona
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Evidence for universal scaling in the spinglass phase
Thomas Jorg ^{1}, Helmut G. Katzgraber ^{2}
Physical Review Letters 101 (2008) 197205
We perform Monte Carlo simulations of Ising spinglass models in three and four dimensions, as well as of MigdalKadanoff spin glasses on a hierarchical lattice. Our results show strong evidence for universal scaling in the spinglass phase in all three models. Not only does this allow for a clean way to compare results obtained from different coupling distributions, it also suggests that a so far elusive renormalization group approach within the spinglass phase may actually be feasible.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Theoretische Physik,
ETH Zurich
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Exact distribution of the maximal height of watermelons
Gregory Schehr ^{1}, Satya N. Majumdar ^{2}, Alain Comtet ^{2}, Julien RandonFurling ^{2}
Physical Review Letters 101 (2008) 150601
We study p non intersecting onedimensional Brownian walks, either excursions (pwatermelons with a wall) or bridges (pwatermelons without wall). We focus on the maximal height H_p of these pwatermelons configurations on the unit time interval. Using path integral techniques associated to corresponding models of free Fermions, we compute exactly the distribution of H_p for generic integer p. For large p, one obtains < H_p > \sim \sqrt{2p} for pwatermelons with a wall whereas < H_p > \sim \sqrt{p} for pwatermelons without wall. We point out and solve a discrepancy between these exact asymptotic behaviors and numerical experiments, which recently attracted much attention, and we show that only the preasymptotic behaviors of these averages were actually measured. In addition, our method, using tools of manybody physics, provides a simpler physical derivation of the connection between vicious walkers and random matrix theory.
 1. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique d'Orsay (LPT),

Exact Minimum Eigenvalue Distribution of an Entangled Random Pure State
Satya N. Majumdar ^{1}, Oriol Bohigas ^{1}, Arul Lakshminarayan ^{2, 3}
Journal of Statistical Physics 131 (2008) 3349
A recent conjecture regarding the average of the minimum eigenvalue of the reduced density matrix of a random complex state is proved. In fact, the full distribution of the minimum eigenvalue is derived exactly for both the cases of a random real and a random complex state. Our results are relevant to the entanglement properties of eigenvectors of the orthogonal and unitary ensembles of random matrix theory and quantum chaotic systems. They also provide a rare exactly solvable case for the distribution of the minimum of a set of N {\em strongly correlated} random variables for all values of N (and not just for large N).
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. MaxPlanckInstitut für Physik komplexer Systeme,
MaxPlanckInstitut  3. Department of Physics,
Indian Institute of Technology Madras
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Exact treatment of excitonpolaron formation by Diagrammatic Monte Carlo
Evgeni Burovski ^{1}, Holger Fehske ^{2}, Andrei S. Mishchenko ^{3, 4}
Physical Review Letters 101 (2008) 116403
We develop an approximationfree Diagrammatic Monte Carlo technique to study fermionic particles interacting with each other simultaneously through both an attractive Coulomb potential and bosonic excitations of the underlying medium. Exemplarily we apply the method to the longstanding excitonpolaron problem and present numerically exact results for the wave function, groundstate energy, binding energy and effective mass of this quasiparticle. Focusing on the electronhole pair boundstate formation, we discuss various limiting cases of a generic excitonpolaron model. The frequently used instantaneous approximation to the retarded interaction due to the phonon exchange is found to be of very limited applicability. For the case of a light electron and heavy hole the system is well approximated by a particle in the field of a static attractive impurity.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Institut Fur Physik,
ErnstMoritzArndtUniversitat Greifswald  3. CMRG CrossCorrelated Materials Research Group,
CMRG  4. "Kurchakov Institute" Russian Research Centre,
Kurchakov Institute
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Exact valence bond entanglement entropy and probability distribution in the XXX spin chain and the Potts model
Jacobsen, J.L., Saleur, H.
Physical Review Letters100 (2008) 087205

Exhaustive enumeration unveils clustering and freezing in random 3SAT
John Ardelius ^{1}, Lenka Zdeborová ^{2}
Physica E: Lowdimensional Systems and Nanostructures 78 (2008) 040101
We study geometrical properties of the complete set of solutions of the random 3satisfiability problem. We show that even for moderate system sizes the number of clusters corresponds surprisingly well with the theoretic asymptotic prediction. We locate the freezing transition in the space of solutions which has been conjectured to be relevant in explaining the onset of computational hardness in random constraint satisfaction problems.
 1. Swedish Institute of Computeur science (SICS),
SICS Swedish Institute of Computeur science  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Swedish Institute of Computeur science (SICS),

Extreme statistics of complex random and quantum chaotic states
Arul Lakshminarayan ^{1}, Steven Tomsovic ^{1}, Oriol Bohigas ^{2}, Satya N. Majumdar ^{2}
Physical Review Letters 100 (2008) 044103
An exact analytical description of extreme intensity statistics in complex random states is derived. These states have the statistical properties of the Gaussian and Circular Unitary Ensemble eigenstates of random matrix theory. Although the components are correlated by the normalization constraint, it is still possible to derive compact formulae for all values of the dimensionality N. The maximum intensity result slowly approaches the Gumbel distribution even though the variables are bounded, whereas the minimum intensity result rapidly approaches the Weibull distribution. Since random matrix theory is conjectured to be applicable to chaotic quantum systems, we calculate the extreme eigenfunction statistics for the standard map with parameters at which its classical map is fully chaotic. The statistical behaviors are consistent with the finiteN formulae.
 1. MaxPlanckInstitut für Physik komplexer Systeme,
MaxPlanckInstitut  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. MaxPlanckInstitut für Physik komplexer Systeme,

Extreme Value Statistics of Eigenvalues of Gaussian Random Matrices
Dean, D.S., Majumdar, S.N.
Physical Review E77 (2008) 0411

Fermions out of Dipolar Bosons in the lowest Landau level
Brice Chung ^{1}, Thierry Jolicoeur ^{1}
Physical Review A: Atomic, Molecular and Optical Physics 77 (2008) 043608
In the limit of very fast rotation atomic BoseEinstein condensates may reside entirely in the lowest twodimensional Landau level (LLL). For small enough filling factor of the LLL, one may have formation of fractional quantum Hall states. We investigate the case of bosons with dipolar interactions as may be realized with Chromium52 atoms. We show that at filling factor equal to unity the ground state is a MooreRead (a.k.a Pfaffian) paired state as is the case of bosons with purely swave scattering interactions. This Pfaffian state is destabilized when the interaction in the swave channel is small enough and the ground state is a stripe phase with unidimensional density modulation. For filling factor 1/3, we show that there is formation of a Fermi sea of ``composite fermions''. These composites are made of one boson bound with three vortices. This phase has a wide range of stability and the effective mass of the fermions depends essentially only of the scattering amplitude in momentum channels larger or equal to 2. The formation of such a Fermi sea opens up a new possible route to detection of the quantum Hall correlations.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Finite Layer Thickness Stabilizes the Pfaffian State for the 5/2 Fractional Quantum Hall Effect: Wavefunction Overlap and Topological Degeneracy
Michael. R. Peterson ^{1}, Th. Jolicoeur ^{2}, S. Das Sarma ^{3}
Physical Review Letters 101 (2008) 016807
We find the finitewidth, i.e., the layer thickness, of experimental quasitwo dimensional systems produces a physical environment sufficient to stabilize the MooreRead Pfaffian state thought to describe the fractional quantum Hall effect at filling factor $\nu=5/2$. This conclusion is based on exact calculations performed in the spherical and torus geometries, studying wavefunction overlap and ground state degeneracy
 1. Condensed Matter theory center, departement of physic.,
Condensed matter theory center  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Condensed Matter Theory Center, Department of Physics,
University of Maryland at College Park
 1. Condensed Matter theory center, departement of physic.,

Fluctuation induced quantum interactions between compact objects and a plane mirror
Thorsten Emig ^{1}
Journal of Statistical Mechanics: Theory and Experiment (2008) P04007
The interaction of compact objects with an infinitely extended mirror plane due to quantum fluctuations of a scalar or electromagnetic field that scatters off the objects is studied. The mirror plane is assumed to obey either Dirichlet or Neumann boundary conditions or to be perfectly reflecting. Using the method of images, we generalize a recently developed approach for compact objects in unbounded space [1,2] to show that the Casimir interaction between the objects and the mirror plane can be accurately obtained over a wide range of separations in terms of charge and current fluctuations of the objects and their images. Our general result for the interaction depends only on the scattering matrices of the compact objects. It applies to scalar fields with arbitrary boundary conditions and to the electromagnetic field coupled to dielectric objects. For the experimentally important electromagnetic Casimir interaction between a perfectly conducting sphere and a plane mirror we present the first results that apply at all separations. We obtain both an asymptotic large distance expansion and the two lowest order correction terms to the proximity force approximation. The asymptotic CasimirPolder potential for an atom and a mirror is generalized to describe the interaction between a dielectric sphere and a mirror, involving higher order multipole polarizabilities that are important at subasymptotic distances.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Geometrical dependence of decoherence by electronic interactions in a GaAs/GaAlAs square network
M. Ferrier ^{1}, A. C. H. Rowe ^{1}, S. Gueron ^{1, 2}, H. Bouchiat ^{1}, C. Texier ^{1, 3}, G. Montambaux ^{1}
Physical Review Letters 100 (2008) 146802
We investigate weak localization in metallic networks etched in a two dimensional electron gas between $25\:$mK and $750\:$mK when electronelectron (ee) interaction is the dominant phase breaking mechanism. We show that, at the highest temperatures, the contributions arising from trajectories that wind around the rings and trajectories that do not are governed by two different length scales. This is achieved by analyzing separately the envelope and the oscillating part of the magnetoconductance. For $T\gtrsim0.3\:$K we find $\Lphi^\mathrm{env}\propto{T}^{1/3}$ for the envelope, and $\Lphi^\mathrm{osc}\propto{T}^{1/2}$ for the oscillations, in agreement with the prediction for a single ring \cite{LudMir04,TexMon05}. This is the first experimental confirmation of the geometry dependence of decoherence due to ee interaction.
 1. Laboratoire de Physique des Solides (LPS),
CNRS : UMR8502 – Université Paris XI  Paris Sud  2. Quantronics group, Service de Physique de l'Etat Condensé, IRAMIS (QUANTRONICS),
CEA : DSM/IRAMIS – CNRS : URA2464  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique des Solides (LPS),

Ground states of colloidal molecular crystals on periodic substrates
Samir El Shawish ^{1}, Jure Dobnikar ^{1}, Emmanuel Trizac ^{2}
Soft Matter 4 (2008) 14911498
Two dimensional suspensions of spherical colloids subject to periodic external fields exhibit a rich variety of molecular crystalline phases. We study in simulations the ground state configurations of dimeric and trimeric systems, that are realized on square and triangular lattices, when either two or three macroions are trapped in each external potential minimum. Bipartite orders of the checkerboard or stripe types are reported together with more complex quadripartite orderings, and the shortcomings of envisioning the colloids gathered in a single potential minimum as a composite rigid object are discussed. This work also sheds light on simplifying assumptions underlying previous theoretical treatments and that made possible the mapping onto spin models.
 1. Jozef Stefan Institute,
Jozef Stefan Institute  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Jozef Stefan Institute,

Ising model with memory: coarsening and persistence properties
Fabio Caccioli ^{1, 2}, Silvio Franz ^{3}, Matteo Marsili ^{4}
Journal of Statistical Mechanics: Theory and Experiment (2008) 07006
We consider the coarsening properties of a kinetic Ising model with a memory field. The probability of a spinflip depends on the persistence time of the spin in a state. The more a spin has been in a given state, the less the spinflip probability is. We numerically studied the growth and persistence properties of such a system on a two dimensional square lattice. The memory introduces energy barriers which freeze the system at zero temperature. At finite temperature we can observe an apparent arrest of coarsening for low temperature and long memory length. However, since the energy barriers introduced by memory are due to local effects, there exists a timescale on which coarsening takes place as for the Ising model. Moreover the two point correlation functions of the Ising model with and without memory are the same, indicating that they belong to the same universality class.
 1. international school for advenced stydy,
international school  2. Istituto Nazionale di Fisica Nucleare,
Istituto Nazionale di Fisica Nucleare  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  4. The Abdus Salam International Centre for Theoretical Physics,
ICTP Trieste
 1. international school for advenced stydy,

Kramers degeneracy in a magnetic field and Zeeman spinorbit coupling in antiferromagnetic conductors
Revaz Ramazashvili ^{1, 2}
Physical Review Letters 101 (2008) 137202
In this article, I study magnetic response of electron wavefunctions in a commensurate collinear antiferromagnet. I show that, at a special set of momenta, hidden antiunitary symmetry protects Kramers degeneracy of Bloch eigenstates against a magnetic field, pointing transversely to staggered magnetization. Hence a substantial momentum dependence of the transverse gfactor in the Zeeman term, turning the latter into a spinorbit coupling, that may be present in materials from chromium to borocarbides, cuprates, pnictides, as well as organic and heavy fermion conductors.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Ecole Normale Supérieure de Paris (ENS),
Ecole Normale Supérieure de Paris  ENS Paris
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

LERW as an Example of OffCritical SLES
Bauer, M., Bernard, D., Kytölä, K.
Journal of Statistical Physics132 (2008) 721754

Localization for onedimensional random potentials with large local fluctuations
Tom Bienaime ^{1}, Christophe Texier ^{1}
Journal of Physics A Mathematical and Theoretical 41 (2008) 475001
We study the localization of wave functions for onedimensional Schrödinger Hamiltonians with random potentials $V(x)$ with short range correlations and large local fluctuations such that $\int\D{x} \smean{V(x)V(0)}=\infty$. A random supersymmetric Hamiltonian is also considered. Depending on how large the fluctuations of $V(x)$ are, we find either new energy dependences of the localization length, $\ell_\mathrm{loc}\propto{}E/\ln{E}$, $\ell_\mathrm{loc}\propto{}E^{\mu/2}$ with $0<\mu<2$ or $\ell_\mathrm{loc}\propto\ln^{\mu1}E$ for $\mu>1$, or superlocalization (decay of the wave functions faster than a simple exponential).
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Locked constraint satisfaction problems
Lenka Zdeborová ^{1}, Marc Mézard ^{1}
Physical Review Letters 101 (2008) 078702
We introduce and study the random 'locked' constraint satisfaction problems. When increasing the density of constraints, they display a broad 'clustered' phase in which the space of solutions is divided into many isolated points. While the phase diagram can be found easily, these problems, in their clustered phase, are extremely hard from the algorithmic point of view: the best known algorithms all fail to find solutions. We thus propose new benchmarks of really hard optimization problems and provide insight into the origin of their typical hardness.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

ManyBody Physics and Quantum Chaos
Denis Ullmo ^{1}
Reports on Progress in Physics 71 (2008) 026001
Experimental progresses in the miniaturisation of electronic devices have made routinely available in the laboratory small electronic systems, on the micron or submicron scale, which at low temperature are sufficiently well isolated from their environment to be considered as fully coherent. Some of their most important properties are dominated by the interaction between electrons. Understanding their behaviour therefore requires a description of the interplay between interference effects and interactions. The goal of this review is to address this relatively broad issue, and more specifically to address it from the perspective of the quantum chaos community. I will therefore present some of the concepts developed in the field of quantum chaos which have some application to study manybody effects in mesoscopic and nanoscopic systems. Their implementation is illustrated on a few examples of experimental relevance such as persistent currents, mesoscopic fluctuations of Kondo properties or Coulomb blockade. I will furthermore try to bring out, from the various physical illustrations, some of the specific advantages on more general grounds of the quantum chaos based approach.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Measuring optical tunneling times using a HongOuMandel interferometer
Papoular, D.J., Cladé, P., Polyakov, S.V., McCormick, C.F., Migdall, A.L., Lett, P.D.
Optics Express16 (2008) 16005

Mesoscopic Fluctuations of the Pairing Gap
S. Åberg ^{1}, H. Olofsson ^{1}, P. Leboeuf ^{2}
AIP Conference Proceedings 995 (2008) 173184
A description of mesoscopic fluctuations of the pairing gap in finitesized quantum systems based on periodic orbit theory is presented. The size of the fluctuations are found to depend on quite general properties. We distinguish between systems where corresponding classical motion is regular or chaotic, and describe in detail fluctuations of the BCS gap as a function of the size of the system. The theory is applied to different mesoscopic systems: atomic nuclei, metallic grains, and ultracold fermionic gases. We also present a detailed description of pairing gap variation with particle number for nuclei based on a deformed cavity potential.
 1. Mathematical Physics (LTH),
Lund University  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Mathematical Physics (LTH),

Multifunctionality and Robustness tradeoffs in model genetic circuits
Martin, O.C., Wagner, A.
Biophysical Journal94 (2008) 29272937

New Routes to Solitons in Quasi OneDimensional Conductors
S. Brazovskii ^{1}
Solid State Sciences 10 (2008) 1786
We collect evidences on existence of microscopic solitons, and their determining role in electronic processes of quasi1D conductors. The ferroelectric charge ordering gives access to several types of solitons in conductivity and permittivity, and to solitons' bound pairs in optics  both in insulating and conducting cases of TMTTF and TMTSF subfamilies. The excursion to physics of conjugated polymers allows to suggest further experiments. Internal tunnelling in Charge Density Waves goes through the channel of 'amplitude solitons', which correspond to the long sought quasiparticle  the spinon. The same experiment gives an access to the reversible reconstruction of the junction via spontaneous creation of a lattice of 2Pi solitons  a grid of dislocations. The individual 2Pi solitons have been visually captured in recent STM experiments. Junctions of organic and oxide conductors are anticipated to show similar effects of reconstruction.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Non Poissonian statistics in a low density fluid
P. Visco ^{1, 2}, F. van Wijland ^{1, 3}, E. Trizac ^{1}
The Journal of Physical Chemistry B 112, 17 (2008) 5412
Our interest goes to the collisional statistics in an arbitrary interacting fluid. We show that even in the low density limit and contrary to naive expectation, the number of collisions experienced by a tagged particle in a given time does not obey Poisson law, and that conversely, the free flight time distribution is not a simple exponential. As an illustration, the hard sphere fluid case is worked out in detail. For this model, we quantify analytically those deviations and successfully compare our predictions against molecular dynamics simulations.
 1. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Matière et Systèmes Complexes (MSC),
CNRS : UMR7057 – Université Paris VII  Paris Diderot
 1. Laboratoire de Physique Théorique d'Orsay (LPT),

Nonmonotonic effects of parallel sidewalls on Casimir forces between cylinders
Sahand Jamal Rahi ^{1}, Alejandro W. Rodriguez ^{1}, Thorsten Emig ^{2, 3}, Robert L. Jaffe ^{4}, Steven G. Johnson ^{5}, Mehran Kardar ^{1}
Physical Review A: Atomic, Molecular and Optical Physics 77 (2008) 030101
We analyze the Casimir force between two parallel infinite metal cylinders, with nearby metal plates (sidewalls), using complementary methods for mutual confirmation. The attractive force between cylinders is shown to have a nonmonotonic dependence on the separation to the plates. This intrinsically multibody phenomenon, which occurs with either one or two sidewalls (generalizing an earlier result for squares between two sidewalls), does not follow from any simple twobody force description. We can, however, explain the nonmonotonicity by considering the screening (enhancement) of the interactions by the fluctuating charges (currents) on the two cylinders, and their images on the nearby plate(s). Furthermore, we show that this effect also implies a nonmonotonic dependence of the cylinderplate force on the cylindercylinder separation.
 1. Department of Physics,
Massachusetts Institute of Technology  2. Institut für Theoretische Physik,,
Universität zu Köln  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  4. Center for Theoretical Physics and Laboratory for Nuclear Science,
Massachusetts Institute of Technology  5. Department of Mathematics,
Massachusetts Institute of Technology
 1. Department of Physics,

Numerical studies of planar closed random walks
Jean Desbois ^{1}, Stephane Ouvry ^{1}
Journal of Statistical Mechanics (2008) 08004
Lattice numerical simulations for planar closed random walks and their winding sectors are presented. The frontiers of the random walks and of their winding sectors have a Hausdorff dimension $d_H=4/3$. However, when properly defined by taking into account the inner 0winding sectors, the frontiers of the random walks have a Hausdorff dimension $d_H\approx 1.77$.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

On the Doubly Refined Enumeration of Alternating Sign Matrices and Totally Symmetric SelfComplementary Plane Partitions
T. Fonseca ^{1}, Paul ZinnJustin ^{1}
The Electronic Journal of Combinatorics 15 (2008) R81
We prove the equality of doubly refined enumerations of Alternating Sign Matrices and of Totally Symmetric SelfComplementary Plane Partitions using integral formulae originating from certain solutions of the quantum KnizhnikZamolodchikov equation.
 1. Laboratoire de Physique Théorique et Hautes Energies (LPTHE),
CNRS : UMR7589 – Université Paris VI  Pierre et Marie Curie – Université Paris VII  Paris Diderot
 1. Laboratoire de Physique Théorique et Hautes Energies (LPTHE),

On the path integral representation for quantum spin models and its application to the quantum cavity method and to Monte Carlo simulations
Krzakala, F., Rosso, A., Smerjian, G., Zamponi, F.
Physical Review B78 (2008) 134428

On the spectrum of the Laplace operator of metric graphs attached at a vertex — Spectral determinant approach
Christophe Texier ^{1, 2}
Journal of Physics A General Physics 41 (2008) 085207
We consider a metric graph $\mathcal{G}$ made of two graphs $\mathcal{G}_1$ and $\mathcal{G}_2$ attached at one point. We derive a formula relating the spectral determinant of the Laplace operator $S_\mathcal{G}(\gamma)=\det(\gamma\Delta)$ in terms of the spectral determinants of the two subgraphs. The result is generalized to describe the attachment of $n$ graphs. The formulae are also valid for the spectral determinant of the Schrödinger operator $\det(\gamma\Delta+V(x))$.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Laboratoire de Physique des Solides (LPS),
CNRS : UMR8502 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

On the spinliquid phase of one dimensional spin1 bosons
F. H. L. Essler ^{1}, G. V. Shlyapnikov ^{2, 3}, A. M. Tsvelik ^{4}
Journal of Statistical Mechanics: Theory and Experiment (2008) 020027
We consider a model of one dimensional spin1 bosons with repulsive densitydensity interactions and antiferromagnetic exchange. We show that the low energy effective field theory is given by a spincharge separated theory of a TomonagaLuttinger Hamiltonian and the O(3) nonlinear sigma model describing collective charge and spin excitations respectively. At a particular ratio of the densitydensity to spinspin interaction the model is integrable, and we use the exact solutions to provide an independent derivation of the low energy effective theory. The system is in a superfluid phase made of singlet pairs of bosons, and we calculate the longdistance asymptotics of certain correlation functions.
 1. The Rudolf Peirls Centre for Theoretical Physics,
University of Oxford  2. Van der WaalsZeeman Institute,
University of Amsterdam  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  4. Department of Condensed Matter Physics and Material Science,
Brookhaven National Laboratory
 1. The Rudolf Peirls Centre for Theoretical Physics,

On the time to reach maximum for a variety of constrained Brownian motions
Majumdar, S.N., RandonFurling, J., Kearney, M.J., Yor, M.
Journal of Physics A41 (2008) 365005

Optimal Time to Sell a Stock in BlackScholes Model: Comment on ‘Thou shall buy and hold’, by A. Shiryaev, Z. Xu and X.Y. Zhou
Satya N. Majumdar ^{1}, JeanPhilippe Bouchaud ^{2}
Quantitative Finance 8 (2008) 753760
We reconsider the problem of optimal time to sell a stock studied recently by Shiryaev, Xu and Zhou using path integral methods. This method allows us to confirm the results obtained by these authors and extend them to a parameter region inaccessible to the method used by Shiryaev et. al. We also obtain the full distribution of the time t_m at which the maximum of the price is reached for arbitrary values of the drift.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Science et Finance,
Science et Finance
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Orbital Landau level dependence of the fractional quantum Hall effect in quasitwo dimensional electron layers: finitethickness effects
Michael R. Peterson ^{1}, Th. Jolicoeur ^{2}, S. Das Sarma ^{3}
Physical Review B 78 (2008) 155308
The fractional quantum Hall effect (FQHE) in the second orbital Landau level at filling factor 5/2 remains enigmatic and motivates our work. We consider the effect of the quasi2D nature of the experimental FQH system on a number of FQH states (fillings 1/3, 1/5, 1/2) in the lowest, second, and third Landau levels (LLL, SLL, TLL,) by calculating the overlap, as a function of quasi2D layer thickness, between the exact ground state of a model Hamiltonian and the consensus variational wavefunctions (Laughlin wavefunction for 1/3 and 1/5 and the MooreRead Pfaffian wavefunction for 1/2). Using large overlap as a stability, or FQHE robustness, criterion we find the FQHE does not occur in the TLL (for any thickness), is the most robust for zero thickness in the LLL for 1/3 and 1/5 and for 11/5 in the SLL, and is most robust at finitethickness (45 magnetic lengths) in the SLL for the mysterious 5/2 state and the 7/3 state. No FQHE is found at 1/2 in the LLL for any thickness. We examine the orbital effects of an inplane (parallel) magnetic field finding its application effectively reduces the thickness and could destroy the FQHE at 5/2 and 7/3, while enhancing it at 11/5 as well as for LLL FQHE states. The inplane field effects could thus be qualitatively different in the LLL and the SLL by virtue of magnetoorbital coupling through the finite thickness effect. In the torus geometry, we show the appearance of the threefold topological degeneracy expected for the Pfaffian state which is enhanced by thickness corroborating our findings from overlap calculations. Our results have ramifications for wavefunction engineeringthe possibility of creating an optimal experimental system where the 5/2 FQHE state is more likely described by the Pfaffian state with applications to topological quantum computing.
 1. Condensed Matter theory center, departement of physic.,
Condensed matter theory center  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Condensed Matter Theory Center, Department of Physics,
University of Maryland at College Park
 1. Condensed Matter theory center, departement of physic.,

Orientation dependence of Casimir forces
T. Emig ^{1, 2}, N. Graham ^{3}, R. L. Jaffe ^{4}, M. Kardar ^{5}
Physical Review A: Atomic, Molecular and Optical Physics 79 (2008) 054901
The Casimir interaction between two objects, or between an object and a plane, depends on their relative orientations. We make these angular dependences explicit by considering prolate or oblate spheroids. The variation with orientation is calculated exactly at asymptotically large distances for the electromagnetic field, and at arbitrary separations for a scalar field. For a spheroid in front of a mirror, the leading term is orientation independent, and we find the optimal orientation from computations at higher order.
 1. Institut für Theoretische Physik,
Universität zu Köln  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Middlebury College,
Middlebury Colleg  4. Department of Physics, Center for Theoretical Physics,
Massachussetts Institute of Technology (MIT)  5. Department of Physics,
Massachusetts Institute of Technology
 1. Institut für Theoretische Physik,

Overlap Interfaces in Hierarchical SpinGlass models
Silvio Franz ^{1}, T Jorg ^{1}, Giorgio Parisi ^{2}
Journal of Statistical Mechanics: Theory and Experiment (2008) 02002
We discuss interfaces in spin glasses. We present new theoretical results and a numerical method to characterize overlap interfaces and the stability of the spinglass phase in extended disordered systems. We use this definition to characterize the low temperature phase of hierarchical spinglass models. We use the Replica Symmetry Breaking theory to evaluate the cost for an overlap interface, which in these models is particularly simple. A comparison of our results from numerical simulations with the theoretical predictions shows good agreement.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Dipartimento di Fisica and INFM,
Università degli studi di Roma I  La Sapienza
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Pairs of SAT Assignments and Clustering in Random Boolean Formulae
Daudé, H., Mezard, M., Mora, T., Toninelli, C.
Theor. Comp. Sci.393 (2008) 260279

Phase Transition in a Random Minima Model: Mean Field Theory and Exact Solution on the Bethe Lattice
Peter Sollich ^{1}, Satya N Majumdar ^{2}, Alan J Bray ^{3}
Journal of Statistical Mechanics: Theory and Experiment (2008) 11011
We consider the number and distribution of minima in random landscapes defined on nonEuclidean lattices. Using an ensemble where random landscapes are reweighted by a fugacity factor $z$ for each minimum they contain, we construct first a `twobox' mean field theory. This exhibits an ordering phase transition at $z\c=2$ above which one box contains an extensive number of minima. The onset of order is governed by an unusual order parameter exponent $\beta=1$, motivating us to study the same model on the Bethe lattice. Here we find from an exact solution that for any connectivity $\mu+1>2$ there is an ordering transition with a conventional mean field order parameter exponent $\beta=1/2$, but with the region where this behaviour is observable shrinking in size as $1/\mu$ in the mean field limit of large $\mu$. We show that the behaviour in the transition region can also be understood directly within a mean field approach, by making the assignment of minima `soft'. Finally we demonstrate, in the simplest mean field case, how the analysis can be generalized to include both maxima and minima. In this case an additional first order phase transition appears, to a landscape in which essentially all sites are either minima or maxima.
 1. department of mathematics,
Department of Mathematics  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. School of Physics and Astronomy,
University of Manchester
 1. department of mathematics,

Phase Transitions and Computational Difficulty in Random Constraint Satisfaction Problems
Florent Krzakala ^{1}, Lenka Zdeborová ^{2}
Journal of Physics: Conference Series 95 (2008) 012012
We review the understanding of the random constraint satisfaction problems, focusing on the qcoloring of large random graphs, that has been achieved using the cavity method of the physicists. We also discuss the properties of the phase diagram in temperature, the connections with the glass transition phenomenology in physics, and the related algorithmic issues.
 1. Laboratoire de PhysicoChimie Théorique (LPCT),
CNRS : UMR7083 – ESPCI ParisTech  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de PhysicoChimie Théorique (LPCT),

Potts Glass on Random Graphs
Florent Krzakala ^{1}, Lenka Zdeborová ^{2}
Europhysics Letters (EPL) 81 (2008) 57005
We solve the qstate Potts model with antiferromagnetic interactions on large random lattices of finite coordination. Due to the frustration induced by the large loops and to the local treelike structure of the lattice this model behaves as a mean field spin glass. We use the cavity method to compute the temperaturecoordination phase diagram and to determine the location of the dynamic and static glass transitions, and of the Gardner instability. We show that for q>=4 the model possesses a phenomenology similar to the one observed in structural glasses. We also illustrate the links between the positive and the zerotemperature cavity approaches, and discuss the consequences for the coloring of random graphs. In particular we argue that in the colorable region the onestep replica symmetry breaking solution is stable towards more steps of replica symmetry breaking.
 1. Laboratoire de PhysicoChimie Théorique (LPCT),
CNRS : UMR7083 – ESPCI ParisTech  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de PhysicoChimie Théorique (LPCT),

Quantum detection of electronic flying qubits
G. Fève ^{1, 2}, Pascal Degiovanni ^{3, 4}, Th. Jolicoeur ^{5}
Physical Review B 77 (2008) 035308
We consider a model of a detector of ballistic electrons at the edge of a twodimensional electron gas in the integer quantum Hall regime. The electron is detected by capacitive coupling to a gate which is also coupled to a passive RC circuit. Using a quantum description of this circuit, we determine the signal over noise ratio of the detector in term of the detector characteristics. The backaction of the detector on the incident wavepacket is then computed using a FeynmanVernon influence functional approach. Using information theory, we define the appropriate notion of quantum limit for such an 'on the fly' detector. We show that our particular detector can approach the quantum limit up to logarithms in the ratio of the measurement time over the RC relaxation time. We argue that such a weak logarithmic effect is of no practical significance. Finally we show that a twoelectron interference experiment can be used to probe the detector induced decoherence.
 1. Laboratoire Pierre Aigrain (LPA),
CNRS : UMR8551 – Université Paris VI  Pierre et Marie Curie – Université Paris VII  Paris Diderot – Ecole Normale Supérieure de Paris  ENS Paris  2. Laboratoire de photonique et de nanostructures (LPN),
CNRS : UPR20  3. Laboratoire de Physique de l'ENS Lyon (PhysENS),
CNRS : UMR5672 – École Normale Supérieure  Lyon  4. Physics Department [Boston] (BUPhysics),
Boston University  5. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire Pierre Aigrain (LPA),

Quantum KnizhnikZamolodchikov Equation, Totally Symmetric SelfComplementary Plane Partitions and Alternating Sign Matrices
P. Di Francesco ^{1}, Paul ZinnJustin ^{2}
Theoretical and Mathematical Physics 154 (2008) 331348
We present multiresidue formulae for partial sums in the basis of link patterns of the polynomial solution to the level 1 U_q(\hat sl_2) quantum KnizhnikZamolodchikov equation at generic values of the quantum parameter q. These allow for rewriting and generalizing a recent conjecture [Di Francesco '06] connecting the above to generating polynomials for weighted Totally Symmetric SelfComplementary Plane Partitions. We reduce the corresponding conjectures to a single integral identity, yet to be proved.
 1. Service de Physique Théorique (SPhT),
CNRS : URA2306 – CEA : DSM/SPHT  2. Laboratoire de Physique Théorique et Hautes Energies (LPTHE),
CNRS : UMR7589 – Université Paris VI  Pierre et Marie Curie – Université Paris VII  Paris Diderot
 1. Service de Physique Théorique (SPhT),

Random AharonovBohm vortices and some exact families of integrals: Part II
Stefan Mashkevich ^{1}, Stéphane Ouvry ^{2}
Journal of statistical mechanicstheory and experiment (2008) P03018
At 6th order in perturbation theory, the random magnetic impurity problem at second order in impurity density narrows down to the evaluation of a single Feynman diagram with maximal impurity line crossing. This diagram can be rewritten as a sum of ordinary integrals and nested double integrals of products of the modified Bessel functions $K_{\nu}$ and $I_{\nu}$, with $\nu=0,1$. That sum, in turn, is shown to be a linear combination with rational coefficients of $(2^51)\zeta(5)$, $\int_0^{\infty} u K_0(u)^6 du$ and $\int_0^{\infty} u^3 K_0(u)^6 du$. Unlike what happens at lower orders, these two integrals are not linear combinations with rational coefficients of Euler sums, even though they appear in combination with $\zeta(5)$. On the other hand, any integral $\int_0^{\infty} u^{n+1} K_0(u)^p (uK_1(u))^q du$ with weight $p+q=6$ and an even $n$ is shown to be a linear combination with rational coefficients of the above two integrals and 1, a result that can be easily generalized to any weight $p+q=k$. A matrix recurrence relation in $n$ is built for such integrals. The initial conditions are such that the asymptotic behavior is determined by the smallest eigenvalue of the transition matrix.
 1. Schrodinger,
Schrodinger  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Schrodinger,

Random subcubes as a toy model for constraint satisfaction problems
Thierry Mora ^{1, 2}, Lenka Zdeborova ^{1}
Journal of Statistical Physics 131 (2008) 11211138
We present an exactly solvable randomsubcube model inspired by the structure of hard constraint satisfaction and optimization problems. Our model reproduces the structure of the solution space of the random ksatisfiability and kcoloring problems, and undergoes the same phase transitions as these problems. The comparison becomes quantitative in the largek limit. Distance properties, as well the xsatisfiability threshold, are studied. The model is also generalized to define a continuous energy landscape useful for studying several aspects of glassy dynamics.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. LewisSigler Institute for Integrative Genomics,
Princeton University
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Real roots of random polynomials and zero crossing properties of diffusion equation
Schehr, G., Majumdar, S.N.
Journal of Statistical Physics132 (2008) 235273

Residual Coulomb interaction fluctuations in chaotic systems: the boundary, random plane waves, and semiclassical theory
Steven Tomsovic ^{1}, Denis Ullmo ^{2}, Arnd Baecker ^{3}
Physical Review Letters 100 (2008) 164101
New fluctuation properties arise in problems where both spatial integration and energy summation are necessary ingredients. The quintessential example is given by the shortrange approximation to the first order ground state contribution of the residual Coulomb interaction. The dominant features come from the region near the boundary where there is an interplay between Friedel oscillations and fluctuations in the eigenstates. Quite naturally, the fluctuation scale is significantly enhanced for Neumann boundary conditions as compared to Dirichlet. Elements missing from random plane wave modeling of chaotic eigenstates lead surprisingly to significant errors, which can be corrected within a purely semiclassical approach.
 1. MaxPlanckInstitut für Physik komplexer Systeme,
MaxPlanckInstitut  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. Institut für Theoretische Physik,,
Technische Universität Dresden
 1. MaxPlanckInstitut für Physik komplexer Systeme,

Semiclassical Theory of BardeenCooperSchrieffer PairingGap Fluctuations
H. Olofsson ^{1}, S. Åberg ^{1}, P. Leboeuf ^{2}
Physical Review Letters 100 (2008) 0370005
Superfluidity and superconductivity are genuine manybody manifestations of quantum coherence. For finitesize systems the associated pairing gap fluctuates as a function of size or shape. We provide a parameter free theoretical description of pairing fluctuations in mesoscopic systems characterized by order/chaos dynamics. The theory accurately describes experimental observations of nuclear superfluidity (regular system), predicts universal fluctuations of superconductivity in small chaotic metallic grains, and provides a global analysis in ultracold Fermi gases.
 1. Mathematical Physics (LTH),
Lund University  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Mathematical Physics (LTH),

Semiclassical theory of nonlocal statistical measures: residual Coulomb interactions
Denis Ullmo ^{1}, Steven Tomsovic ^{1, 2, 3}, Arnd Baecker ^{4}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 79 (2008) 056217
In a recent letter [Phys. Rev. Lett. {\bf 100}, 164101 (2008)] and within the context of quantized chaotic billiards, random plane wave and semiclassical theoretical approaches were applied to an example of a relatively new class of statistical measures, i.e. measures involving both complete spatial integration and energy summation as essential ingredients. A quintessential example comes from the desire to understand the shortrange approximation to the first order ground state contribution of the residual Coulomb interaction. Billiards, fully chaotic or otherwise, provide an ideal class of systems on which to focus as they have proven to be successful in modeling the single particle properties of a LandauFermi liquid in typical mesoscopic systems, i.e. closed or nearly closed quantum dots. It happens that both theoretical approaches give fully consistent results for measure averages, but that somewhat surprisingly for fully chaotic systems the semiclassical theory gives a much improved approximation for the fluctuations. Comparison of the theories highlights a couple of key shortcomings inherent in the random plane wave approach. This paper contains a complete account of the theoretical approaches, elucidates the two shortcomings of the oftreliedupon random plane wave approach, and treats nonfully chaotic systems as well.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. MaxPlanckInstitut für Physik komplexer Systeme,
MaxPlanckInstitut  3. Department of Physics,
Washington State University  4. Institut für Theoretische Physik,,
Technische Universität Dresden
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Simple Glass Models and their Quantum Annealing
Thomas Jorg ^{1}, Florent Krzakala ^{2}, Jorge Kurchan ^{3}, A. C. Maggs ^{2}
Physical Review Letters 101 (2008) 147204
We study first order quantum phase transitions in meanfield spin glasses. We solve the quantum Random Energy Model using elementary methods and show that at the transition the eigenstate suddenly projects onto the unperturbed ground state and that the gap between the lowest states is exponentially small in the system size. We argue that this is a generic feature of all `Random First Order' models, which includes benchmarks such as random satisfiability. We introduce a twotime instanton to calculate this gap in general, and discuss the consequences for quantum annealing.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Laboratoire de PhysicoChimie Théorique (LPCT),
CNRS : UMR7083 – ESPCI ParisTech  3. Physique et mécanique des milieux hétérogenes (PMMH),
CNRS : UMR7636 – Université Paris VI  Pierre et Marie Curie – Université Paris VII  Paris Diderot – ESPCI ParisTech
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Spin glass models with Kac interactions
Silvio Franz ^{1}
European Physical Journal B 64 (2008) 557561
In this paper I will review my work on disordered systems spin glass model with two body and $p>2$ body interactions with long but finite interaction range $R$. I will describe the relation of these model with Mean Field Theory in the Kac limit and some attempts to go beyond mean field.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Stability of dark solitons in three dimensional dipolar BoseEinstein condensates
R. Nath ^{1}, P. Pedri ^{2, 3}, L. M.N.B.F. Santos ^{1}
Physical Review Letters 101 (2008) 210402
The dynamical stability of dark solitons in dipolar BoseEinstein condensates is studied. For standard shortrange interacting condensates dark solitons are unstable against transverse excitations in two and three dimensions. On the contrary, due to its non local character, the dipolar interaction allows for stable 3D stationary dark solitons, opening a qualitatively novel scenario in nonlinear atom optics. We discuss in detail the conditions to achieve this stability, which demand the use of an additional optical lattice, and the stability regimes.
 1. Institut fur Theoretische Physik,
Leibniz Universität Hannover  2. Laboratoire de Physique Théorique de la Matière Condensée (LPTMC),
CNRS : UMR7600 – Université Paris VI  Pierre et Marie Curie  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Institut fur Theoretische Physik,

Stability of the fermionic gases close to a pwave Feshbach resonance
J. Levinsen ^{1}, N. R. Cooper ^{2}, V. Gurarie ^{3}
Physical Review A: Atomic, Molecular and Optical Physics 78 (2008) 063616
We study the stability of the paired fermionic pwave superfluid made out of identical atoms all in the same hyperfine state close to a pwave Feshbach resonance. First we reproduce known results concerning the lifetime of a 3D superfluid, in particular, we show that it decays at the same rate as its interaction energy, thus precluding its equilibration before it decays. Then we proceed to study its stability in case when the superfluid is confined to 2D by means of an optical harmonic potential. We find that the relative stability is somewhat improved in 2D in the BCS regime, such that the decay rate is now slower than the appropriate interaction energy scale. The improvement in stability, however, is not dramatic and one probably needs to look for other mechanisms to suppress decay to create a long lived 2D pwave fermionic superfluid.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. TCM Group, Cavendish Laboratory,
Cavendish Laboratory Cambridge  3. Department of physics, University of Colorado,
University of Colorado
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Statistical Physics of Group Testing
Mezard, M., Tarzia, M., Toninelli, C.
Journal of Statistical Physics131 (2008) 783801

Statistical Properties of the Final State in Onedimensional Ballistic Aggregation
Satya N. Majumdar ^{1}, Kirone Mallick ^{2}, Sanjib Sabhapandit ^{3}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 79 (2008) 021109
We investigate the long time behaviour of the onedimensional ballistic aggregation model that represents a sticky gas of N particles with random initial positions and velocities, moving deterministically, and forming aggregates when they collide. We obtain a closed formula for the stationary measure of the system which allows us to analyze some remarkable features of the final `fan' state. In particular, we identify universal properties which are independent of the initial position and velocity distributions of the particles. We study cluster distributions and derive exact results for extreme value statistics (because of correlations these distributions do not belong to the GumbelFrechetWeibull universality classes). We also derive the energy distribution in the final state. This model generates dynamically many different scales and can be viewed as one of the simplest exactly solvable model of Nbody dissipative dynamics.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Service de Physique Théorique (SPhT),
CNRS : URA2306 – CEA : DSM/SPHT  3. Raman Research Institute,
Raman Research Insitute
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Statistics of the total number of collisions and the ordering time in a freely expanding hardpoint gas
Sanjib Sabhapandit ^{1}, Ioana Bena ^{2}, Satya N. Majumdar ^{1}
Journal of statistical mechanicstheory and experiment (2008) P05012
We consider a Jepsen gas of $N$ hardpoint particles undergoing free expansion on a line, starting from random initial positions of the particles having random initial velocities. The particles undergo binary elastic collisions upon contact and move freely inbetween collisions. After a certain ordering time $T_{o}$, the system reaches a ``fan'' state where all the velocities are completely ordered from left to right in an increasing fashion and there is no further collision. We compute analytically the distributions of (i) the total number of collisions and (ii) the ordering time $T_{o}$. We show that several features of these distributions are universal.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. department of theoretical physics,
University of Geneva
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Structure and thermodynamics of a ferrofluid bilayer
Carlos Alvarez ^{1, 2}, Martial Mazars ^{1}, JeanJacques Weis ^{1}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 77 (2008) 051501
We present extensive Monte Carlo simulations for the thermodynamic and structural properties of a planar bilayer of dipolar hard spheres for a wide range of densities, dipole moments and layer separations. Expressions for the stress and pressure tensors of the bilayer system are derived. For all thermodynamic states considered the interlayer energy is shown to be attractive and much smaller than the intralayer contribution to the energy. It vanishes at layer separations of the order of two hard sphere diameters. The normal pressure is negative and decays as a function of layer separation $h$ as $1/h^5$. Intralayer and interlayer pair distribution functions and angular correlation functions are presented. Despite the weak interlayer energy strong positional and orientational correlations exist between particles in the two layers.
 1. Laboratoire de Physique Théorique d'Orsay (LPT),
CNRS : UMR8627 – Université Paris XI  Paris Sud  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique d'Orsay (LPT),

Superfluid pairing between fermions with unequal masses
M. A. Baranov ^{1, 2, 3}, C. Lobo ^{4}, G. V. Shlyapnikov ^{5}
Physical Review B 78 (2008) 033620
We consider a superfluid state in a twocomponent gas of fermionic atoms with equal densities and unequal masses in the BCS limit. We develop a perturbation theory along the lines proposed by Gorkov and MelikBarkhudarov and find that for a large difference in the masses of heavy ($M$) and light ($m$) atoms one has to take into account both the secondorder and thirdorder contributions. The result for the critical temperature and order parameter is then quite different from the prediction of the simple BCS approach. Moreover, the small parameter of the theory turns out to be $(p_{F}a)/\hbar)\sqrt{M/m}\ll1$, where $p_{F}$ is the Fermi momentum, and $a$ the scattering length. Thus, for a large mass ratio $M/m$ the conventional perturbation theory requires significantly smaller Fermi momenta (densities) or scattering lengths than in the case of $M\sim m$, where the small parameter is $(p_{F}a)/\hbar)\ll1$. We show that 3body scattering resonances appearing at a large mass ratio due to the presence of 3body bound Efimov states do not influence the result, which in this sense becomes universal.
 1. Van der WaalsZeeman Institute,
Van der WaalsZeeman Institute  2. Institut für Quantenoptik und Quanteninformation,
Institut für Quantenoptik und Quanteninformation  3. National Research Centre "Kurchatov Institute" (NRC KI),
University of Moscow  4. School of Physics and Astronomy,
University of Nottingham  5. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Van der WaalsZeeman Institute,

The Mott metalinsulator transition in the 1D Hubbard model in an external magnetic field
Holger Frahm ^{1}, Temo Vekua ^{2}
Journal of statistical mechanicstheory and experiment (2008) P01007
We study the low energy behavior of the one dimensional Hubbard model across the Mott metalinsulator phase transition in an external magnetic field. In particular we calculate elements of the dressed charge matrix at the critical point of the Mott transition for arbitrary Hubbard repulsion and magnetization numerically and, in certain limiting cases, analytically. These results are combined with a nonperturbative effective field theory approach to reveal how the breaking of time reversal symmetry influences the Mott transition.
 1. Institut fur Theoretische Physik,
Leibniz Universitat Hannover  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Institut fur Theoretische Physik,

Theory of subgap interchain tunneling in quasi onedimensional conductors
S. Brazovskii ^{1, 2}, S. I. Matveenko ^{1, 2}
Physical Review B 77 (2008) 155432
We suggest a theory of internal coherent tunneling in the pseudogap region, when the applied voltage U is below the free electron gap 2Delta_0. We address quasi 1D systems, where the gap is originated by spontaneous lattice distortions of the Incommensurate Charge Density Wave (ICDW) type. Results can be adjusted also to quasi1D superconductors. The instanton approach allows to calculate the interchain tunneling current both in single electron (amplitude solitons, i.e. spinons) and bielectron (phase slips) channels. Transition rates are governed by a dissipative dynamics originated by emission of gapless phase excitations in the course of the instanton process. We find that the singleelectron tunneling is allowed below the nominal gap 2Delta_0 down to the true pairbreaking threshold at 2W_as<2Delta, where W_as=2Delta/pi is the amplitude soliton energy. Most importantly, the bielectronic tunneling stretches down to U=0 (in the 1D regime). In both cases, the threshold behavior is given by power laws J (UU_c)^beta, where the exponent beta v_F/u is large as the ratio of the Fermi velocity v_F and the phase one u. In the 2D or 3D ordered phases, at temperature T
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. L.D. Landau Institute for Theoretical Physics,
Landau Institute for Theoretical Physics
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Thermal Effects in the dynamics of disordered elastic systems
S. Bustingorry ^{1}, A. B. Kolton ^{2}, A. Rosso ^{3}, W. Krauth ^{4}, T. Giamarchi ^{5}
Physica B: Condensed Matter 404 (2008) 444446
Many seemingly different macroscopic systems (magnets, ferroelectrics, CDW, vortices,..) can be described as generic disordered elastic systems. Understanding their static and dynamics thus poses challenging problems both from the point of view of fundamental physics and of practical applications. Despite important progress many questions remain open. In particular the temperature has drastic effects on the way these systems respond to an external force. We address here the important question of the thermal effect close to depinning, and whether these effects can be understood in the analogy with standard critical phenomena, analogy so useful to understand the zero temperature case. We show that close to the depinning force temperature leads to a rounding of the depinning transition and compute the corresponding exponent. In addition, using a novel algorithm it is possible to study precisely the behavior close to depinning, and to show that the commonly accepted analogy of the depinning with a critical phenomenon does not fully hold, since no divergent lengthscale exists in the steady state properties of the line below the depinning threshold.
 1. Centro Atomico Bariloche,
Centro Atomico  2. Centro Atomico Bariloche,
Centro Atómico Bariloche  3. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  4. Laboratoire de Physique Statistique de l'ENS (LPS),
CNRS : UMR8550 – Université Paris VI  Pierre et Marie Curie – Université Paris VII  Paris Diderot – Ecole Normale Supérieure de Paris  ENS Paris  5. DPMC (DPMCMaNEP),
University of Geneva
 1. Centro Atomico Bariloche,

Trace formula for dieletric cavities : I. General properties
E. Bogomolny ^{1}, R. Dubertrand ^{1}, C. Schmit ^{1}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 78 (2008) 056202
The construction of the trace formula for open dielectric cavities is examined in detail. Using the Krein formula it is shown that the sum over cavity resonances can be written as a sum over classical periodic orbits for the motion inside the cavity. The contribution of each periodic orbit is the product of the two factors. The first is the same as in the standard trace formula and the second is connected with the product of reflection coefficients for all points of reflection with the cavity boundary. Two asymptotic terms of the smooth resonance counting function related with the area and the perimeter of the cavity are derived. The coefficient of the perimeter term differs from the one for closed cavities due to unusual highenergy asymptotics of the $\mathbf{S}$matrix for the scattering on the cavity. Corrections to the leading semiclassical formula are briefly discussed. Obtained formulas agree well with numerical calculations for circular dielectric cavities.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Tunable correlations in a 2×2 hermitian random matrix model
Vivo, P., Majumdar, S.N.
Physica A387 (2008) 48394855

Twocomponent repulsive Fermi gases with population imbalance in elongated harmonic traps
M. ColoméTatché ^{1}
Physical Review A: Atomic, Molecular and Optical Physics 78 (2008) 033612
We study the twocomponent repulsive Fermi gas with imbalanced populations in one dimension. Starting from the Bethe Ansatz solution we calculate analytically the phase diagram for the homogeneous system. We show that two phases appear: the fully polarised phase and the partially polarised phase. By means of the local density approximation and the equation of state for the homogeneous system we calculate the density profile for the harmonically confined case. We show that a twoshell structure appears: at the center of the cloud we find the partially polarised phase and at the edges the fully polarised one. The radii of the inner and outer shells are calculated for different values of the polarisation and the coupling strength. We calculate the dependence of the magnetisation on the polarisation for different values of the coupling strength and we show that the susceptibility is always finite.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Unbiased sampling of globular lattice proteins in three dimensions
Jacobsen, J.L.
Physical Review Letters100 (2008) 118102

Universal Record Statistics of Random Walks and Lévy Flights
Satya N. Majumdar ^{1}, Robert M. Ziff ^{2}
Physical Review Letters 101 (2008) 050601
It is shown that statistics of records for time series generated by random walks are independent of the details of the jump distribution, as long as the latter is continuous and symmetric. In N steps, the mean of the record distribution grows as the sqrt(4N/pi) while the standard deviation grows as sqrt((24/pi) N), so the distribution is nonselfaveraging. The mean shortest and longest duration records grow as sqrt(N/pi) and 0.626508... N, respectively. The case of a discrete random walker is also studied, and similar asymptotic behavior is found.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Michigan Center for Theoretical Physics and Department of chemical Engineering,
University of MichiganAnn Arbor
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Universality and universal finitesize scaling functions in fourdimensional Ising spin glasses
Thomas Jorg ^{1}, Helmut G. Katzgraber ^{2}
Physical Review B 77 (2008) 214426
We study the fourdimensional Ising spin glass with Gaussian and bonddiluted bimodal distributed interactions via largescale Monte Carlo simulations and show via an extensive finitesize scaling analysis that fourdimensional Ising spin glasses obey universality.
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  2. Theoretische Physik,
ETH Zurich
 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),

Unzipping of two random heteropolymers: Ground state energy and finite size effects
M. V. Tamm ^{1}, S. K. Nechaev ^{2}
Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 78 (2008) 011903
We have analyzed the dependence of average ground state energy per monomer, $e$, of the complex of two random heteropolymers with quenched sequences, on chain length, $n$, in the ensemble of chains with uniform distribution of primary sequences. Every chain monomer is randomly and independently chosen with the uniform probability distribution $p=1/c$ from a set of $c$ different types A, B, C, D, .... Monomers of the first chain could form saturating reversible bonds with monomers of the second chain. The bonds between similar monomer types (like AA, BB, CC, etc.) have the attraction energy $u$, while the bonds between different monomer types (like AB, AD, BD, etc.) have the attraction energy $v$. The main attention is paid to the computation of the normalized free energy $e(n)$ for intermediate chain lengths, $n$, and different ratios $a=\frac{v}{u}$ at sufficiently low temperatures when the entropic contribution of the loop formation is negligible compared to direct energetic interactions between chain monomers and the partition function of the chains is dominated by the ground state. The performed analysis allows one to derive the force, $f$, which is necessary to apply for unzipping of two random heteropolymer chains of equal lengths whose ends are separated by the distance $x$, averaged over all equally distributed primary structures at low temperatures for fixed values $a$ and $c$.
 1. Physics Department,
Moscow State University  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud
 1. Physics Department,

Wetting transition on a onedimensional disorder
D. M. Gangardt ^{1}, S. K. Nechaev ^{2, 3}
Journal of Statistical Physics 130 (2008) 483502
We consider wetting of a onedimensional random walk on a halfline $x\ge 0$ in a shortranged potential located at the origin $x=0$. We demonstrate explicitly how the presence of a quenched chemical disorder affects the pinningdepinning transition point. For small disorders we develop a perturbative technique which enables us to compute explicitly the averaged temperature (energy) of the pinning transition. For strong disorder we compute the transition point both numerically and using the renormalization group approach. Our consideration is based on the following idea: the random potential can be viewed as a periodic potential with the period $n$ in the limit $n\to\infty$. The advantage of our approach stems from the ability to integrate exactly over all spatial degrees of freedoms in the model and to reduce the initial problem to the analysis of eigenvalues and eigenfunctions of some special nonHermitian random matrix with disorderdependent diagonal and constant offdiagonal coefficients. We show that even for strong disorder the shift of the averaged pinning point of the random walk in the ensemble of random realizations of substrate disorder is indistinguishable from the pinning point of the system with preaveraged (i.e. annealed) Boltzmann weight.
 1. School of Physics and Astronomy, University of Birmingham,
University of Birmingham  2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI  Paris Sud  3. P.N. Lebedev Institute,
The Russian Academy of Science
 1. School of Physics and Astronomy, University of Birmingham,

Dipole Oscillations of a BoseEinstein Condensate in the Presence of Defects and Disorder
M. AlbertT. PaulN. Pavloff ^{1} P. Leboeuf ^{1}
Physical Review Letters, American Physical Society, 2008, 100 (25), 〈10.1103/PhysRevLett.100.250405〉
 1. LPTMS  Laboratoire de Physique Théorique et Modèles Statistiques

Archive ouverte HAL – In response to comment on ‘A congruence index for testing topological similarity between trees’
Damien De Vienne ^{1} Tatiana Giraud ^{2} Olivier C Martin ^{3, 4, 5, 6}
Bioinformatics, Oxford University Press (OUP), 2008, 25 (1), pp.150151
 1. LBBE  Laboratoire de Biométrie et Biologie Evolutive
 2. ESE  Ecologie Systématique et Evolution
 3. LPTMS  Laboratoire de Physique Théorique et Modèles Statistiques
 4. GQELe Moulon  Génétique Quantitative et Evolution  Le Moulon (Génétique Végétale)
 5. BIOSP  Biostatistique et Processus Spatiaux
 6. IS2  Statistical Inference for Industry and Health

In response to comment on ‘A congruence index for testing topological similarity between trees’
Damien De Vienne ^{1} Tatiana Giraud ^{2} Olivier C Martin ^{3, 4, 5, 6}
Bioinformatics, Oxford University Press (OUP), 2008, 25 (1), pp.150151
 1. LBBE  Laboratoire de Biométrie et Biologie Evolutive
 2. ESE  Ecologie Systématique et Evolution
 3. LPTMS  Laboratoire de Physique Théorique et Modèles Statistiques
 4. GQELe Moulon  Génétique Quantitative et Evolution  Le Moulon (Génétique Végétale)
 5. BIOSP  Biostatistique et Processus Spatiaux
 6. IS2  Statistical Inference for Industry and Health

Archive ouverte HAL – Dipole Oscillations of a BoseEinstein Condensate in the Presence of Defects and Disorder
M. AlbertT. PaulN. Pavloff ^{1} P. Leboeuf ^{1}
Physical Review Letters, American Physical Society, 2008, 100 (25), 〈10.1103/PhysRevLett.100.250405〉
 1. LPTMS  Laboratoire de Physique Théorique et Modèles Statistiques

A functional central limit theorem for interacting particle systems on transitive graphs – Archive ouverte HAL
Paul Doukhan ^{1, 2} Gabriel Lang ^{3} Sana Louhichi ^{4} Bernard Ycart ^{5, 6}
Paul Doukhan, Gabriel Lang, Sana Louhichi, Bernard Ycart. A functional central limit theorem for interacting particle systems on transitive graphs. Markov Processes And Related Fields, Polymat Publishing Company, 2008, 14 (1), pp.79114. ⟨hal00268278⟩
A finite range interacting particle system on a transitive graph is considered. Assuming that the dynamics and the initial measure are invariant, the normalized empirical distribution process converges in distribution to a centered diffusion process. As an application, a central limit theorem for certain hitting times, interpreted as failure times of a coherent system in reliability, is derived.
 1. SAMOS  Statistique Appliquée et MOdélisation Stochastique
 2. CES  Centre d'économie de la Sorbonne
 3. MIAParis  Mathématiques et Informatique Appliquées
 4. LPTMS  Laboratoire de Physique Théorique et Modèles Statistiques
 5. SMS  Statistique et Modélisation Stochatisque
 6. MAP5  UMR 8145  Mathématiques Appliquées Paris 5

Bethe Ansatz in the Bernoulli Matching Model of Random Sequence Alignment – Archive ouverte HAL
Satya N. Majumdar ^{1} Kirone Mallick ^{2} Sergei Nechaev ^{1}
Satya N. Majumdar, Kirone Mallick, Sergei Nechaev. Bethe Ansatz in the Bernoulli Matching Model of Random Sequence Alignment. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2008, 77, pp.011110. ⟨10.1103/PhysRevE.77.011110⟩. ⟨hal00226439⟩
For the Bernoulli Matching model of sequence alignment problem we apply the Bethe ansatz technique via an exact mapping to the 5vertex model on a square lattice. Considering the terracelike representation of the sequence alignment problem, we reproduce by the Bethe ansatz the results for the averaged length of the Longest Common Subsequence in Bernoulli approximation. In addition, we compute the average number of nucleation centers of the terraces.
 1. LPTMS  Laboratoire de Physique Théorique et Modèles Statistiques
 2. SPhT  Service de Physique Théorique

Archive ouverte HAL – Bethe Ansatz in the Bernoulli Matching Model of Random Sequence Alignment
Satya N. Majumdar ^{1} Kirone Mallick ^{2} Sergei Nechaev ^{1}
Satya N. Majumdar, Kirone Mallick, Sergei Nechaev. Bethe Ansatz in the Bernoulli Matching Model of Random Sequence Alignment. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2008, 77, pp.011110. ⟨10.1103/PhysRevE.77.011110⟩. ⟨hal00226439⟩
For the Bernoulli Matching model of sequence alignment problem we apply the Bethe ansatz technique via an exact mapping to the 5vertex model on a square lattice. Considering the terracelike representation of the sequence alignment problem, we reproduce by the Bethe ansatz the results for the averaged length of the Longest Common Subsequence in Bernoulli approximation. In addition, we compute the average number of nucleation centers of the terraces.
 1. LPTMS  Laboratoire de Physique Théorique et Modèles Statistiques
 2. SPhT  Service de Physique Théorique

Archive ouverte HAL – A functional central limit theorem for interacting particle systems on transitive graphs
Paul Doukhan ^{1, 2} Gabriel Lang ^{3} Sana Louhichi ^{4} Bernard Ycart ^{5, 6}
Paul Doukhan, Gabriel Lang, Sana Louhichi, Bernard Ycart. A functional central limit theorem for interacting particle systems on transitive graphs. Markov Processes And Related Fields, Polymat Publishing Company, 2008, 14 (1), pp.79114. ⟨hal00268278⟩
A finite range interacting particle system on a transitive graph is considered. Assuming that the dynamics and the initial measure are invariant, the normalized empirical distribution process converges in distribution to a centered diffusion process. As an application, a central limit theorem for certain hitting times, interpreted as failure times of a coherent system in reliability, is derived.
 1. SAMOS  Statistique Appliquée et MOdélisation Stochastique
 2. CES  Centre d'économie de la Sorbonne
 3. MIAParis  Mathématiques et Informatique Appliquées
 4. LPTMS  Laboratoire de Physique Théorique et Modèles Statistiques
 5. SMS  Statistique et Modélisation Stochatisque
 6. MAP5  UMR 8145  Mathématiques Appliquées Paris 5