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arXiv 0906.2695cond-mat.dis-nncond-mat.stat-mech
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聚类变分法

Replica Cluster Variational Method

T. Rizzo, A. Lage-Castellanos, R. Mulet, F. Ricci-Tersenghi

摘要:

我们提出了一个一般的形式主义,使复制对称和复制对称破坏的背景下菊池的集群变分方法(CVM)。利用CVM的复制和信息传递公式,我们得到了具有淬火无序的系统的复制自由能的平均和单样本的变分表达式,并用场函数的泛函表示信息进行了层次分析.我们开始研究在顺磁复制对称相中考虑元格近似的Edwards-Anderson模型的平均自由能的方法。在二维情况下,我们发现Bethe近似的伪自旋玻璃相变消失,顺磁相在所有三个规则的二维晶格中稳定到零温度。自由能和其他各种量的定量估计改进了贝特近似。我们提供了物理解释的信念在复制对称相的无序分布的本地哈密顿。相反,这些信息不承认这样的解释,事实上,它们不能被表示为与贝特近似不同的自旋玻璃相的粒子群。

英文摘要:

We present a general formalism to make the Replica-Symmetric and Replica-Symmetry-Breaking ansatz in the context of Kikuchi's Cluster Variational Method (CVM). Using replicas and the message-passing formulation of CVM we obtain a variational expression of the replicated free energy of a system with quenched disorder, both averaged and on a single sample, and make the hierarchical ansatz using functionals of functions of fields to represent the messages. We begin to study the method considering the plaquette approximation to the averaged free energy of the Edwards-Anderson model in the paramagnetic Replica-Symmetric phase. In two dimensions we find that the spurious spin-glass phase transition of the Bethe approximation disappears and the paramagnetic phase is stable down to zero temperature in all the three regular 2D lattices. The quantitative estimates of the free energy and of various other quantities improve those of the Bethe approximation. We provide the physical interpretation of the beliefs in the replica-symmetric phase as disorder distributions of the local Hamiltonians. The messages instead do not admit such an interpretation and indeed they cannot be represented as populations in the spin-glass phase at variance with the Bethe approximation.

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