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arXiv 0810.5438cond-mat.stat-mechcond-mat.dis-nn
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自平均和临界性:二维随机键自旋模型的比较研究

Self-averaging and criticality: A comparative study in 2d random bond spin models

N G Fytas, A Malakis

摘要:

通过Wang-Landau(WL)算法,研究了猝灭键随机性对二维Ising自旋模型自平均性质的影响.研究了具有最近邻和次最近邻竞争相互作用的超反铁磁(SAF)正方形模型的随机键形式和相应的简单铁磁伊辛模型.我们发现,随机键SAF模型表现出强烈的违反自平均,远远强于观察到的情况下的随机键伊辛模型。我们对样本相关伪临界温度分布方差的渐进标度行为的分析发现与Aharony和Harris的重整化群预测一致。使用这种替代方法,我们发现的相关长度指数$ν$的估计与从通常的有限尺寸标度(FSS)方法获得的结果一致。

英文摘要:

We investigate and contrast, via the Wang-Landau (WL) algorithm, the effects of quenched bond randomness on the self-averaging properties of two Ising spin models in 2d. The random bond version of the superantiferromagnetic (SAF) square model with nearest- and next-nearest-neighbor competing interactions and the corresponding version of the simple ferromagnetic Ising model are studied. We find that, the random bond SAF model shows a strong violation of self-averaging, much stronger than that observed in the case of the random bond Ising model. Our analysis of the asymptotic scaling behavior of the variance of the distribution of the sample-dependent pseudocritical temperatures is found to be consistent with the renormalization group prediction of Aharony and Harris. Using this alternative approach, we find estimates of the correlation length exponent $ν$ in agreement with results obtained from the usual finite-size scaling (FSS) methodology.

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