1,058 research outputs found
Comment on ``Triviality of the Ground State Structure in Ising Spin Glasses''
We show that the evidence of cond-mat/9906323 does not discriminate among
droplet model and mean field like behavior.Comment: 1 page comment with two .ps figures included. Rewritten version, one
error correcte
Comment on "Ising Spin Glasses in a Magnetic Field"
In ref. cond-mat/9811419 Houdayer and Martin analyze the T=0 3d EA spin glass
with a magnetic field . By using a new, powerful method, they determine an
effective critical field as a function of the lattice size . They use
their results to deduce that the model is behaving like in the droplet approach
and not like the mean-field theory. We show here, by using some unpublished
data, that this very interesting method and numerical results are completely
compatible with the behavior implied by the Replica Symmetry Breaking theory.Comment: One page comment about ref. cond-mat/9811419, including two eps
figure
Off-Equilibrium Dynamics of a 4D Spin Glass with Asymmetric Couplings
We study the off-equilibrium dynamics of the Edwards-Anderson spin glass in
four dimensions under the influence of a non-hamiltonian perturbation. We find
that for small asymmetry the model behaves as the hamiltonian one, while for
large asymmetry the behaviour of the model can be well described by an
interrupted aging scenario. The autocorrelation function C(t_w+\tau,t_w) scales
as \tau/t_w^\beta, with \beta a function of the asymmetry. For very long
waiting times the previous regime crosses over to a time translational
invariant regime (TTI) with stretched exponential relaxation. The model does
not show signs of reaching a TTI regime for weak asymmetry, but in the aging
regime the exponent \beta is always different from one, showing a non trivial
aging scenario.Comment: Latex, 12 pages, 9 figure
Equilibrium valleys in spin glasses at low temperature
We investigate the 3-dimensional Edwards-Anderson spin glass model at low
temperature on simple cubic lattices of sizes up to L=12. Our findings show a
strong continuity among T>0 physical features and those found previously at
T=0, leading to a scenario with emerging mean field like characteristics that
are enhanced in the large volume limit. For instance, the picture of space
filling sponges seems to survive in the large volume limit at T>0, while
entropic effects play a crucial role in determining the free-energy degeneracy
of our finite volume states. All of our analysis is applied to equilibrium
configurations obtained by a parallel tempering on 512 different disorder
realizations. First, we consider the spatial properties of the sites where
pairs of independent spin configurations differ and we introduce a modified
spin overlap distribution which exhibits a non-trivial limit for large L.
Second, after removing the Z_2 (+-1) symmetry, we cluster spin configurations
into valleys. On average these valleys have free-energy differences of O(1),
but a difference in the (extensive) internal energy that grows significantly
with L; there is thus a large interplay between energy and entropy
fluctuations. We also find that valleys typically differ by sponge-like space
filling clusters, just as found previously for low-energy system-size
excitations above the ground state.Comment: 10 pages, 8 figures, RevTeX format. Clarifications and additional
reference
Low T Dynamical Properties of Spin Glasses Smoothly Extrapolate to T=0
We compare ground state properties of 3D Ising Spin Glasses with Gaussian
couplings with results from off-equilibrium numerical simulations at non zero
(but low) temperatures. We find that the non-zero temperature properties of the
system smoothly connect to the T=0 behavior, confirming the point of view that
results established at T=0 typically also give relevant information about the
physics of the system.Comment: 14 pages and 4 ps figure
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
Numerical Simulations of the 4D Edwards-Anderson Spin Glass with Binary Couplings
We present numerical results that allow a precise determination of the
transition point and of the critical exponents of the 4D Edwards-Anderson Spin
Glass with binary quenched random couplings. We show that the low T phase
undergoes Replica Symmetry Breaking. We obtain results on large lattices, up to
a volume : we use finite size scaling to show the relevance of our
results in the infinite volume limit.Comment: 18 pages + 17 figures, revised bibliography and minor typos. Added
Journal Re
Tempered Fermions in the Hybrid Monte Carlo Algorithm
Parallel tempering simulates at many quark masses simultaneously, by changing
the mass during the simulation while remaining in equilibrium. The algorithm is
faster than pure HMC if more than one mass is needed, and works better the
smaller the smallest mass is.Comment: 4 pages, 2 figures, Combined proceedings for Lattice 97, Edinburgh
and the International Workshop 'Lattice QCD on Parallel Computers',
University of Tsukuba, Japa
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