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arXiv 1005.4491cond-mat.dis-nncond-mat.stat-mech
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二维+- J伊辛模型玻璃态转变的普适性

Universality of the glassy transitions in the two-dimensional +- J Ising model

Francesco Parisen Toldin, Andrea Pelissetto, Ettore Vicari

摘要:

本文研究了正方晶格+- J伊辛模型的零温玻璃化转变,键分布为$P(J_{xy}) = p δ(J_{xy} - J) + (1-p) δ(J_{xy} + J)$ ; p=1和p=1/2分别对应于纯伊辛模型和对称双峰分布的伊辛自旋玻璃.我们提出了有限温度蒙特卡罗模拟在p=4/5,这是接近低温顺磁-铁磁转变线位于p=0.89,并在p=1/2。它们的比较提供了强有力的证据,即对于$1-p_0<p<p_0$,$p_0=0.897$发生的玻璃态临界行为是普遍的,即,独立的p。此外,我们表明,玻璃和磁性模式不耦合在多临界零温度点的顺磁-铁磁转变线和T=0玻璃转变线满足。在理论方面,我们讨论了有限尺寸标度的有效性,在玻璃系统的零温度转变和离散的哈密顿谱。由于在足够低的温度下在有限体积中发生的冻结现象,以$TL^{1/ν}$表示的标准有限尺寸标度极限不存在:重整化群不变量$ξ/L$应被用作基本变量。

英文摘要:

We investigate the zero-temperature glassy transitions in the square-lattice +- J Ising model, with bond distribution $P(J_{xy}) = p δ(J_{xy} - J) + (1-p) δ(J_{xy} + J)$; p=1 and p=1/2 correspond to the pure Ising model and to the Ising spin glass with symmetric bimodal distribution, respectively. We present finite-temperature Monte Carlo simulations at p=4/5, which is close to the low-temperature paramagnetic-ferromagnetic transition line located at p=0.89, and at p=1/2. Their comparison provides a strong evidence that the glassy critical behavior that occurs for $1-p_0<p<p_0$, $p_0=0.897$, is universal, i.e., independent of p. Moreover, we show that glassy and magnetic modes are not coupled at the multicritical zero-temperature point where the paramagnetic-ferromagnetic transition line and the T=0 glassy transition line meet. On the theoretical side we discuss the validity of finite-size scaling in glassy systems with a zero-temperature transition and a discrete Hamiltonian spectrum. Because of a freezing phenomenon which occurs in a finite volume at sufficiently low temperatures, the standard finite-size scaling limit in terms of $TL^{1/ν}$ does not exist: the renormalization-group invariant quantity $ξ/L$ should be used instead as basic variable.

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