1,726 research outputs found
On the existence of a finite-temperature transition in the two-dimensional gauge glass
Results from Monte Carlo simulations of the two-dimensional gauge glass
supporting a zero-temperature transition are presented. A finite-size scaling
analysis of the correlation length shows that the system does not exhibit
spin-glass order at finite temperatures. These results are compared to earlier
claims of a finite-temperature transition.Comment: 4 pages, 2 figure
Finite Size Scaling and ``perfect'' actions: the three dimensional Ising model
Using Finite-Size Scaling techniques, we numerically show that the first
irrelevant operator of the lattice theory in three dimensions
is (within errors) completely decoupled at . This interesting
result also holds in the Thermodynamical Limit, where the renormalized coupling
constant shows an extraordinary reduction of the scaling-corrections when
compared with the Ising model. It is argued that Finite-Size Scaling analysis
can be a competitive method for finding improved actions.Comment: 13 pages, 3 figure
Zero Temperature Glass Transition in the Two-Dimensional Gauge Glass Model
We investigate dynamic scaling properties of the two-dimensional gauge glass
model for the vortex glass phase in superconductors with quenched disorder.
From extensive Monte Carlo simulations we obtain static and dynamic finite
size scaling behavior, where the static simulations use a temperature exchange
method to ensure convergence at low temperatures. Both static and dynamic
scaling of Monte Carlo data is consistent with a glass transition at zero
temperature. We study a dynamic correlation function for the superconducting
order parameter, as well as the phase slip resistance. From the scaling of
these two functions, we find evidence for two distinct diverging correlation
times at the zero temperature glass transition. The longer of these time scales
is associated with phase slip fluctuations across the system that lead to
finite resistance at any finite temperature, while the shorter time scale is
associated with local phase fluctuations.Comment: 8 pages, 10 figures; v2: some minor correction
Numerical studies of the two- and three-dimensional gauge glass at low temperature
We present results from Monte Carlo simulations of the two- and
three-dimensional gauge glass at low temperature using the parallel tempering
Monte Carlo method. Our results in two dimensions strongly support the
transition being at T_c=0. A finite-size scaling analysis, which works well
only for the larger sizes and lower temperatures, gives the stiffness exponent
theta = -0.39 +/- 0.03. In three dimensions we find theta = 0.27 +/- 0.01,
compatible with recent results from domain wall renormalization group studies.Comment: 7 pages, 10 figures, submitted to PR
Scaling and finte-size-scaling in the two dimensional random-coupling Ising ferromagnet
It is shown by Monte Carlo method that the finite size scaling (FSS) holds in
the two dimensional random-coupled Ising ferromagnet. It is also demonstrated
that the form of universal FSS function constructed via novel FSS scheme
depends on the strength of the random coupling for strongly disordered cases.
Monte Carlo measurements of thermodynamic (infinite volume limit) data of the
correlation length () up to along with measurements of
the fourth order cumulant ratio (Binder's ratio) at criticality are reported
and analyzed in view of two competing scenarios. It is demonstrated that the
data are almost exclusively consistent with the scenario of weak universality.Comment: 9 pages, 4figuer
The four dimensional site-diluted Ising model: a finite-size scaling study
Using finite-size scaling techniques, we study the critical properties of the
site-diluted Ising model in four dimensions. We carry out a high statistics
Monte Carlo simulation for several values of the dilution. The results support
the perturbative scenario: there is only the Ising fixed point with large
logarithmic scaling corrections. We obtain, using the Perturbative
Renormalization Group, functional forms for the scaling of several observables
that are in agreement with the numerical data.Comment: 30 pages, 8 postscript figure
The three-dimensional randomly dilute Ising model: Monte Carlo results
We perform a high-statistics simulation of the three-dimensional randomly
dilute Ising model on cubic lattices with . We choose a
particular value of the density, x=0.8, for which the leading scaling
corrections are suppressed. We determine the critical exponents, obtaining , , , and ,
in agreement with previous numerical simulations. We also estimate numerically
the fixed-point values of the four-point zero-momentum couplings that are used
in field-theoretical fixed-dimension studies. Although these results somewhat
differ from those obtained using perturbative field theory, the
field-theoretical estimates of the critical exponents do not change
significantly if the Monte Carlo result for the fixed point is used. Finally,
we determine the six-point zero-momentum couplings, relevant for the
small-magnetization expansion of the equation of state, and the invariant
amplitude ratio that expresses the universality of the free-energy
density per correlation volume. We find .Comment: 34 pages, 7 figs, few correction
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