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arXiv 1406.3200cond-mat.dis-nncond-mat.stat-mech
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拉伸指数相互作用模型的无限无序临界点

Infinite-disorder critical points of models with stretched exponential interactions

Róbert Juhász

摘要:

我们表明,相互作用衰减的距离,$J(l)\sim e^{-cl^a}$,作为一个拉伸指数函数,是能够改变具有无限无序临界点的短程系统的普遍性类。为此,我们利用强无序重整化群(SDRG)方法研究了具有上述相互作用形式的无规横场伊辛链的低能性质。当$0<a<1/2$满足时,我们得到了该模型的临界行为由不同于短程不动点的无限无序不动点控制。在这个范围内,分析计算的临界指数由一个简化的SDRG计划被发现与$a$不同,而对于$a>1/2$,该模型属于相同的普适性类作为其短程变体。大小为$L$的块的纠缠熵随$L$在临界点的增加而增加,但与短程模型相反,前因子在$0<a<1/2$范围内是无序依赖的。用改进的SDRG格式得到的数值结果与解析预测一致。同样的固定点,预计描述的关键行为,其中包括随机接触过程与拉伸指数衰减激活率。

英文摘要:

We show that an interaction decaying as a stretched exponential function of the distance, $J(l)\sim e^{-cl^a}$, is able to alter the universality class of short-range systems having an infinite-disorder critical point. To do so, we study the low-energy properties of the random transverse-field Ising chain with the above form of interaction by a strong-disorder renormalization group (SDRG) approach. We obtain that the critical behavior of the model is controlled by infinite-disorder fixed points different from that of the short-range one if $0<a<1/2$. In this range, the critical exponents calculated analytically by a simplified SDRG scheme are found to vary with $a$, while, for $a>1/2$, the model belongs to the same universality class as its short-range variant. The entanglement entropy of a block of size $L$ increases logarithmically with $L$ in the critical point but, as opposed to the short-range model, the prefactor is disorder-dependent in the range $0<a<1/2$. Numerical results obtained by an improved SDRG scheme are found to be in agreement with the analytical predictions. The same fixed points are expected to describe the critical behavior of, among others, the random contact process with stretched exponentially decaying activation rates.

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