Critical relaxation of the temperature in a square lattice Ising system

Tsuyoshi Horiguchi

T. Schneider, E. Stoll, Kurt Binder

We report computer simulations of critical slowing down in a two-dimensional kinetic Ising system consisting of a square $n\ifmmode\times\else\texttimes\fi{}n$ lattice with periodic boundary conditions. The results for the divergence of the relaxation times disagree with the predictions of the dynamical scaling hypothesis and with recent estimates obtained from a high-temperature expansion method.

Nobuyasu Ito

Nalina Vadakkayil, Massimiliano Esposito, Jan Meibohm

We explore the critical properties of the recently discovered finite-time dynamical phase transition in the nonequilibrium relaxation of Ising magnets after a temperature quench. The transition is characterized by a sudden switch in the relaxation dynamics and it occurs at a sharp critical time. While previous works have focused either on mean-field interactions or on investigating the critical time, we analyze the critical fluctuations at the phase transition in the nearest-neighbor Ising model on a square lattice using Monte Carlo simulations. By means of a finite-size scaling analysis, we extract the critical exponents for the transition. In two spatial dimensions, we find that the exponents are consistent with those of the two-dimensional Ising universality class when the system is initially in the vicinity of the critical point. For initial temperatures below the critical one, however, the critical exponents differ from the Ising-exponents, indicating a distinct dynamical critical phenomenon.

Viktor Urumov

Hideo Yahata

A markoffian stochastic model of interacting Ising spins is discussed near its critical point. The long time behavior of relaxation of its magnetization and energy is investigated near T c by the use of high-temperature series expansion and the ratio method. The numerical estimate of the critical exponent Δ M M of slowing down of magnetization is made, the results of which show Δ M M ≃2 for the simple square and triangular lattices, and Δ M M ≃1.4 for the simple cubic lattice. The exponent Δ E E of slowing down of energy is also estimated, which gives the result Δ E E ≃2 for the simple square and triangular lattices. The method to derive high-temperature expansion of an n -spin correlation function <σ 1 σ 2 …σ n > for an Ising model of spin 1/2 by the use of an equation of detailed balance is presented and applied to these estimates.