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arXiv 0711.3673cond-mat.dis-nncond-mat.stat-mech
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三维随机稀释伊辛模型中的静动力结构因子

Static and dynamic structure factors in three-dimensional randomly diluted Ising models

Pasquale Calabrese, Andrea Pelissetto, Ettore Vicari

摘要:

考虑三维随机稀释伊辛模型,研究了高温相顺磁-铁磁相变时静态和动态自旋-自旋关联函数(静态和动态结构因子)的临界行为.我们考虑一个没有守恒律的纯弛豫动力学,即所谓的模型A。我们提出了蒙特卡罗模拟和微扰场论计算。虽然静态结构因子的临界行为与纯伊辛系统中发生的临界行为非常相似,但动态结构因子显示出实质上不同的临界行为。特别地,动态关联函数显示出与动量无关的大时间衰减率。这种效应与格里菲斯尾的存在无关,格里菲斯尾预计在临界限中不相关,而是与平移不变性的破坏有关,平移不变性发生在任何样品中,并且在临界点处,即使在无序平均之后也不能恢复。

英文摘要:

We consider the three-dimensional randomly diluted Ising model and study the critical behavior of the static and dynamic spin-spin correlation functions (static and dynamic structure factors) at the paramagnetic-ferromagnetic transition in the high-temperature phase. We consider a purely relaxational dynamics without conservation laws, the so-called model A. We present Monte Carlo simulations and perturbative field-theoretical calculations. While the critical behavior of the static structure factor is quite similar to that occurring in pure Ising systems, the dynamic structure factor shows a substantially different critical behavior. In particular, the dynamic correlation function shows a large-time decay rate which is momentum independent. This effect is not related to the presence of the Griffiths tail, which is expected to be irrelevant in the critical limit, but rather to the breaking of translational invariance, which occurs for any sample and which, at the critical point, is not recovered even after the disorder average.

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