4,320 research outputs found
Liquid-glass transition in equilibrium
We show in numerical simulations that a system of two coupled replicas of a
binary mixture of hard spheres undergoes a phase transition in equilibrium at a
density slightly smaller than the glass transition density for an unreplicated
system. This result is in agreement with the theories that predict that such a
transition is a precursor of the standard ideal glass transition. The critical
properties are compatible with those of an Ising system. The relations of this
approach to the conventional approach based on configurational entropy are
briefly discussed.Comment: 5 pages, 3 figures, version accepted for publication in the Physical
Review
Glue Ball Masses and the Chameleon Gauge
We introduce a new numerical technique to compute mass spectra, based on
difference method and on a new gauge fixing procedure. We show that the method
is very effective by test runs on a lattice gauge theory.Comment: latex format, 10 pages, 4 figures added in uufiles forma
-dimensional Arrays of Josephson Junctions, Spin Glasses and -deformed Harmonic Oscillators
We study the statistical mechanics of a -dimensional array of Josephson
junctions in presence of a magnetic field. In the high temperature region the
thermodynamical properties can be computed in the limit , where
the problem is simplified; this limit is taken in the framework of the mean
field approximation. Close to the transition point the system behaves very
similar to a particular form of spin glasses, i.e. to gauge glasses. We have
noticed that in this limit the evaluation of the coefficients of the high
temperature expansion may be mapped onto the computation of some matrix
elements for the -deformed harmonic oscillator
A pedagogical introduction to the replica method for fragile glasses
In this note I present a simplified version of the recent computation (Mezard
and Parisi 1998, 1999) of the properties of glasses in the low temperature
phase in the framework of the replica theory, using an extension of the tools
used in liquid theory. I will only consider here the case of the internal
energy at T=0, which can be studied in a simple way without introducing
replicas.Comment: 7 pages, 1 figure Talk given at Andalo, March 1999; minor errors have
been correcte
Replica analysis of partition-function zeros in spin-glass models
We study the partition-function zeros in mean-field spin-glass models. We
show that the replica method is useful to find the locations of zeros in a
complex parameter plane. For the random energy model, we obtain the phase
diagram in the plane and find that there are two types of distribution of
zeros: two-dimensional distribution within a phase and one-dimensional one on a
phase boundary. Phases with a two-dimensional distribution are characterized by
a novel order parameter defined in the present replica analysis. We also
discuss possible patterns of distributions by studying several systems.Comment: 23 pages, 12 figures; minor change
Small Window Overlaps Are Effective Probes of Replica Symmetry Breaking in 3D Spin Glasses
We compute numerically small window overlaps in the three dimensional Edwards
Anderson spin glass. We show that they behave in the way implied by the Replica
Symmetry Breaking Ansatz, that they do not qualitatively differ from the full
volume overlap and do not tend to a trivial function when increasing the
lattice volume. On the contrary we show they are affected by small finite
volume effects, and are interesting tools for the study of the features of the
spin glass phase.Comment: 9 pages plus 5 figure
On the Use of Optimized Monte Carlo Methods for Studying Spin Glasses
We start from recently published numerical data by Hatano and Gubernatis
cond-mat/0008115 to discuss properties of convergence to equilibrium of
optimized Monte Carlo methods (bivariate multi canonical and parallel
tempering). We show that these data are not thermalized, and they lead to an
erroneous physical picture. We shed some light on why the bivariate multi
canonical Monte Carlo method can fail.Comment: 6 pages, 5 eps figures include
Temperature chaos in 3D Ising Spin Glasses is driven by rare events
Temperature chaos has often been reported in literature as a rare-event
driven phenomenon. However, this fact has always been ignored in the data
analysis, thus erasing the signal of the chaotic behavior (still rare in the
sizes achieved) and leading to an overall picture of a weak and gradual
phenomenon. On the contrary, our analysis relies on a large-deviations
functional that allows to discuss the size dependencies. In addition, we had at
our disposal unprecedentedly large configurations equilibrated at low
temperatures, thanks to the Janus computer. According to our results, when
temperature chaos occurs its effects are strong and can be felt even at short
distances.Comment: 5 pages, 5 figure
On the most compact regular lattice in large dimensions: A statistical mechanical approach
In this paper I will approach the computation of the maximum density of
regular lattices in large dimensions using a statistical mechanics approach.
The starting point will be some theorems of Roger, which are virtually unknown
in the community of physicists. Using his approach one can see that there are
many similarities (and differences) with the problem of computing the entropy
of a liquid of perfect spheres. The relation between the two problems is
investigated in details. Some conjectures are presented, that need further
investigation in order to check their consistency.Comment: 27 page
Four loop results for the 2D O(n) nonlinear sigma model with 0-loop and 1-loop Symanzik actions
We present complete three loop results and preliminary four loop results for
the 2D O(n) nonlinear sigma model with 0-loop and 1-loop Symanzik improved
actions. This calculation aims to test the improvement in the numerical
precision that the combination of Symanzik actions and effective couplings can
give in Monte Carlo simulations.Comment: LATTICE99(spin models). 3 pages, contains espcrc2.sty fil
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