Hasil untuk "cond-mat.dis-nn"

Andrea Montanari, Federico Ricci-Tersenghi, Guilhem Semerjian

Message passing algorithms have proved surprisingly successful in solving hard constraint satisfaction problems on sparse random graphs. In such applications, variables are fixed sequentially to satisfy the constraints. Message passing is run after each step. Its outcome provides an heuristic to make choices at next step. This approach has been referred to as `decimation,' with reference to analogous procedures in statistical physics. The behavior of decimation procedures is poorly understood. Here we consider a simple randomized decimation algorithm based on belief propagation (BP), and analyze its behavior on random k-satisfiability formulae. In particular, we propose a tree model for its analysis and we conjecture that it provides asymptotically exact predictions in the limit of large instances. This conjecture is confirmed by numerical simulations.

Pierluigi Contucci, Cristian Giardinà, Claudio Giberti et al.

This reply shows that the argument presented in the comment by Jorg and Krzakala (cond mat 0709.0894) cannot be used to weaken the results presented in our paper on ultrametricity evidence in the 3d Edwards Anderson model (PRL 99, 057206, 2007; cond-mat/0607376). Our work in fact was mainly based on identifying the scaling law that governs the large volume approach to ultrametricity while NO asymptotic analysis has been done in (cond mat 0709.0894). We show here that the same method we used in our paper, when properly applied to the 2d case, reveals the expected lack of RSB picture at positive temperature, despite the fact that for a fixed finite volume some ultrametric features might still be seen in the joint overlap probability distribution. Those features disappear for increasing volume or when the system is away from the critical curve in the (T,d) plane.

Georges Bouzerar, Richard Bouzerar

We comment on the recent paper "Large-Scale Monte Carlo Study of a Realistic Lattice Model for Ga_(1-x)Mn_xAs" by Y. Yildirim, G. Alvarez, A. Moreo and E. Dagotto", Phys Rev. Lett.{\bf 99}, 057207 (2007); cond-mat/0612002

I. M. Suslov

In the recent series of papers (cond-mat/0402471, cond-mat/0403618, cond-mat/0407618, cond-mat/0501586), Janis and Kolorenc discussed the role of the diffision poles in the Anderson transition theory. Their picture contradicts the general principles and is shown below to be completely misleading. Correct setting of the problem is given and the contemporary situation is discussed. The critical remarks are given on the relation of the diffusion coefficient with multifractality of the wave functions.

Matteo Palassini, A. P. Young

This is a reply to cond-mat/0010033 by Newman and Stein, which is a comment on on our paper Phys. Rev. Lett. 85, 3017 (2000), cond-mat/0002134.

A. Pagnani, G. Parisi, F. Ricci-Tersenghi

We reply to the Comment by Hartmann (cond-mat/9908132) on our paper Phys. Rev. Lett. 84 (2000) 2026 (also cond-mat/9907125).

I. A. Fomin

The argument of V.P.Mineev and M.E.Zhitomirsky is based on unjustified omission of contribution of fluctuations to the free energy of superfluid 3He in aerogel.

E. Marinari, G. Parisi

We show that the evidence of cond-mat/9906323 does not discriminate among droplet model and mean field like behavior.

P. E. Jönsson, H. Yoshino, P. Nordblad

Reply to the Comment by L. Berthier and J.-P. Bouchaud, Phys. Rev. Lett. 90, 059701 (2003), also cond-mat/0209165, on our paper Phys. Rev. Lett. 89, 097201 (2002), also cond-mat/0203444

V. P. Mineev, M. E. Zhitomirsky

We argue that the inhomogeneous A-phase in aerogel is energetically more preferable than the "robust" phase suggested by I. A. Fomin, JETP Lett. 77, 240 (2003); cond-mat/0302117 and cond-mat/0401639.

E. Kanzieper

Recent developments [Kamenev and Mezard, cond-mat/9901110, cond-mat/9903001; Yurkevich and Lerner, cond-mat/9903025; Zirnbauer, cond-mat/9903338] have revived a discussion about applicability of the replica approach to description of spectral fluctuations in the context of random matrix theory and beyond. The present paper, concentrating on invariant non-Gaussian random matrix ensembles with orthogonal, unitary and symplectic symmetries, aims to demonstrate that both the bosonic and the fermionic replicas are capable of reproducing nonperturbative fluctuation formulas for spectral correlation functions in entire energy scale, including the self-correlation of energy levels, provided no sigma-model mapping is used.

I. A. Fomin

The arguments of Volovik are refuted.

S. Das Sarma, E. H. Hwang

This is a Reply to the Comment (cond-mat/9812331) by Kravchenko et al. on our earlier work (cond-mat/9812216).

I. M. Suslov

In the recent review article, P.Markos admits that practically all numerical results on the critical behavior near the Anderson transition are in conflict with analytical expectations, but no serious discussion of this fact is given. The aim of the present comment is to give an analysis of the arising situation.

F. Zamponi

This Ph.D. thesis is divided in two parts. The first one concerns the equilibrium properties of glassy systems. Some aspects of the phenomenology of glasses and of theories attempting to describe them are reviewed in chapter 1. A study of the glass transition of the Hard Sphere liquid based on a replica trick and on the HNC approximation (following Mezard and Parisi) is presented in chapter 2 (cond-mat/0506445). A study of the correlation between fragility and vibrational properties of the minima of the energy landscape in p-spin mean field models is presented in chapter 3 (cond-mat/0401450). The second part of the thesis concerns some recent attempts - reviewed in chapter 4 - to build a statistical theory of a class of nonequilibrium stationary states, based on the "chaotic hypothesis" of Cohen and Gallavotti. In chapter 5 the fluctuation relation, that follows from the chaotic hypothesis for reversible systems, is succesfully tested at the non-Gaussian level in a numerical simulation of a system of particles interacting via a Lennard-Jones--like potential and subjected to an external driving force and to an isokinetic constraint (cond-mat/0412455). In chapter 7 an extension of the fluctuation relation to non-equilibrium relaxational systems driven by external forces (whose dynamics is discussed in chapter 6) is investigated in a simple case (cond-mat/0504750) and the results are compared with numerical simulations on binary Lennard-Jones mixtures (cond-mat/0403579). All the results collected in this thesis already appeared on cond-mat. They are presented here in a (kind of) self-consistent way.

Ludovic Berthier, Jean-Philippe Bouchaud

Comment on the paper P. E. Jonsson, H. Yoshino, and P. Nordblad, Phys. Rev. Lett. 89, 097201 (2002), also cond-mat/0203444.

Jesper Lykke Jacobsen

We numerically calculate the exponent for the disorder averaged and fixed-sample decay of the energy-energy correlator in the q-state random-bond Potts model. Our results are in good agreement with a two-loop expansion (cond-mat/9910181) around q=2 recently found from perturbative renormalisation group techniques, fulfill the correlation length bound ν>= 2/d, and give further evidence against replica symmetry breaking in this class of models.

I. L. Aleiner, B. L. Altshuler, M. G. Vavilov

We point out that the structure of the self-energy suggested in cond-mat/0208140 as a result of a ``non-perturbative analysis'' by ``purely mathematical means'' is incompatible with the very definition of the self-energy.

Marc Barthelemy

In a previous Letter (cond-mat/0106565), Goh et al have presented a numerical study of the load--or betweenness centrality--distribution in a scale-free network whose degree distribution follows a power law with a tunable exponent $γ$. They showed that the load $\ell$ is distributed according to a power-law with exponent $δ$. The authors claimed that $δ$ is universal, ie. independent of the exponent $γ$. In this comment, we use two different ways of checking numerically this universality and we show that it does not hold.

V. Gurarie, A. Zee

This preprint has been withdrawn as crucial errors have been discovered in the papers it has referred to. It is now superseded by cond-mat/9807391.