Determination of the nonlinear relaxation exponent: A Monte Carlo study

Masatoshi Mori

The energy relaxation in the two-dimensional Ising model, with temperature greater than ${\mathit{T}}_{\mathit{c}}$ and in a spin system having a 5120\ifmmode\times\else\texttimes\fi{}5120 lattice, is studied using supercomputer-conducted Monte Carlo simulation. The critical exponents of the linear and nonlinear relaxation times of the internal energy are respectively estimated to be ${\mathrm{\ensuremath{\Delta}}}_{\mathit{E}}^{(\mathit{l})}$=2.064\ifmmode\pm\else\textpm\fi{}0.026 and ${\mathrm{\ensuremath{\Delta}}}_{\mathit{E}}^{(\mathrm{nl})}$=1.132\ifmmode\pm\else\textpm\fi{}0.080, being consistent with the Racz scaling law ${\mathrm{\ensuremath{\Delta}}}_{\mathit{E}}^{(\mathit{l})}$-${\mathrm{\ensuremath{\Delta}}}_{\mathit{E}}^{(\mathrm{nl})}$=1-\ensuremath{\alpha}, where \ensuremath{\alpha} is the critical exponent of the specific heat. Based on the author's previous result in which the critical exponent of the linear relaxation for magnetization was determined as ${\mathrm{\ensuremath{\Delta}}}_{\mathit{M}}^{(\mathit{l})}$=2.076\ifmmode\pm\else\textpm\fi{}0.005, it is strongly suggested that ${\mathrm{\ensuremath{\Delta}}}_{\mathit{E}}^{(\mathit{l})}$=${\mathrm{\ensuremath{\Delta}}}_{\mathit{M}}^{(\mathit{l})}$.

Richard Bausch, H. K. Janssen, Y. Yamazaki

O. F. de Alcantara Bonfim

The Monte Carlo method is used to determine the nonlinear dynamic critical exponent z ( q ) for the q -state Potts model in two dimensions. From the power-law relaxation behaviour of the magnetization we find z (2) = 2.16 ± 0.05, z (3) = 2.16 ± 0.04 and z (4) = 2.18 ± 0.03, suggesting that the critical exponent z is independent of q , as opposed to previous calculations.

Nobuyasu Ito, S. Fukushima, H. Watanabe +1 more

Jian‐Sheng Wang

Masatoshi Mori, Yoshinori Tsuda

The relaxation of the two-dimensional Ising model above ${T}_{c}$ for lattices with size up to 10 240\ifmmode\times\else\texttimes\fi{}10 240 is studied by the Monte Carlo simulation in vectorized super-spin-coding on the HITAC S-810/20 supercomputer. The present estimation of the dynamic critical exponent z gives z=2.076\ifmmode\pm\else\textpm\fi{}0.005, which is equal to the critical exponent ${\ensuremath{\Delta}}^{(l)}$ of the linear relaxation time in a two-dimensional system. Also, the critical exponent, ${\ensuremath{\Delta}}^{(\mathrm{nl})}$ of the nonlinear relaxation time is obtained: ${\ensuremath{\Delta}}^{(\mathrm{nl})=1.932\ifmmode\pm\else\textpm\fi{}0.018}$. These results support the Racz scaling law ${\ensuremath{\Delta}}^{(l)}$=${\ensuremath{\Delta}}^{(\mathrm{nl})+\mathrm{\ensuremath{\beta}}}$ (\ensuremath{\beta} is the critical exponent of the order parameter).