Minority spin dynamics in non-homogeneous Ising model: diverging timescales and exponents
Pratik Mullick, Parongama Sen
备注：
The results presented in this paper have been later improved by generating new data especially closer to x = 0.5. A re-analysis of the scaling collapse leads to the value 1.269 for $ν$. The estimate of $\tilde{z}$ using this value is $\simeq$ 1.82. Hence it can not be strongly stated that $\tilde{z}$ is different from 2
We investigate the dynamical behaviour of the Ising model under a zero temperature quench with the initial fraction of up spins $0\leq x\leq 1$. In one dimension, the known results for persistence probability are verified; it shows algebraic decay for both up and down spins asymptotically with different exponents. It is found that the conventional finite size scaling is valid here. In two dimensions however, the persistence probabilities are no longer algebraic; in particular for $x\leq 0.5$, persistence for the up (minority) spins shows the behaviour $P_{min}(t) \sim t^{-γ}\exp(-(t/τ)^δ)$ with time $t$, while for the down (majority) spins, $P_{maj}(t)$ approaches a finite value. We find that the timescale $τ$ diverges as $(x_c-x)^{- λ}$, where $x_c=0.5$ and $λ\simeq2.31$. The exponent $γ$ varies as $θ_{2d}+c_0(x_c-x)^β$ where $θ_{2d}\simeq0.215$ is very close to the persistence exponent in two dimensions; $β\simeq1$. The results in two dimensions can be understood qualitatively by studying the exit probability, which for different system size is found to have the form $E(x) = f\big[(\frac{x-x_c}{x_c})L^{1/ν}\big]$, with $ν\approx 1.47$. This result suggests that $τ\sim L^{\tilde{z}}$, where $\tilde{z} = \fracλν = 1.57 \pm 0.11$ is an exponent not explored earlier.
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School of Computational & Integrative Sciences, Jawaharlal Nehru University（贾瓦哈拉尔·尼赫鲁大学计算与综合科学学院）；Department of Physics, SRM University - AP（SRM大学安得拉邦分校物理系）
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