213 research outputs found
Finite size scaling and first order phase transition in a modified XY-model
Monte Carlo simulation has been performed in a two-dimensional modified
XY-model first proposed by Domany et. al [E. Domany, M. Schick and R. H.
Swendsen, Phys. Rev. Lett. 52, 1535 (1984)]. The cluster algorithm of Wolff has
been used and multiple histogram reweighting is performed. The first order
scaling behavior of the quantities like specific heat, order parameter
susceptibility and free energy barrier are found to be obeyed accurately. While
the lowest order correlation function was found to decay to zero at long
distance just above the transition, the next higher order correlation function
shows a non-zero plateau.Comment: 18 pages, 10 figures, Accepted for publication in Phys. Rev.
Role of topological defects in the phase transition of modified XY model : A Monte Carlo study
Monte Carlo simulation has been performed on a classical two dimensional XY-
model with a modified form of interaction potential to investigate the role of
topological defects on the phase transition exhibited by the model. In
simulations in a restricted ensemble without defects, the system appears to
remain ordered at all temperatures. Suppression of topological defects on the
square plaquettes in the modified XY- model leads to complete elimination of
the phase transition observed in this model.Comment: 19 pages, 12 figures, Accepted for publication in Phys. Rev.
Local and global persistence exponents of two quenched continuous lattice spin models
Local and global persistence exponents associated with zero temperature
quenched dynamics of two dimensional XY model and three dimensional Heisenberg
model have been estimated using numerical simulations. We have used the method
of block persistence to find both global and local exponents simultaneously (in
a single simulation). Temperature universality of both the exponents for three
dimensional Heisenberg model has been confirmed by simulating the stochastic
(with noise) version of the equation of motion. The noise amplitudes added were
small enough to retain the dynamics below criticality. In the second part of
our work we have studied scaling associated with correlated persistence sites
in the three dimensional Heisenberg model in the later stages of the dynamics.
The relevant length scale associated with correlated persistent sites was found
to behave in a manner similar to the dynamic length scale associated with the
phase ordering dynamics.Comment: 20 pages, 7 figure
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