arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.09496cond-mat.stat-mech
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含扩散对接触过程的耦合两种群模型

A coupled two-species model for the pair contact process with diffusion

Shengfeng Deng, Wei Li, Uwe C. Täuber

摘要:

由2 B -> 3 B,2 B -> 0和扩散粒子扩散定义的接触扩散过程(PCPD)表现出一种不寻常的活性到吸收相变,其普适性一直存在争议。多项研究表明,可能需要明确的粒子对自由度的帐户,以正确地捕捉这个系统的有效的长时间,大规模的行为。我们引入了一个两种群表示,其中单个粒子B和粒子对A根据随机反应B + B -> A,A -> A + B,A -> 0和A -> B + B耦合。平均场分析表明,相变是由两个物种之间的竞争和平衡。我们采用蒙特卡罗模拟,以证明该模型捕捉相关的PCPD功能。在不活跃阶段,A粒子迅速消失,留下B粒子进行纯对湮灭动力学。在临界状态下,A和B密度都以与PCPD序参量相同的指数衰减,并在临界尺寸2以上显示平均场标度。在一个维度上,从种子模拟获得的B物种的临界指数与先前报道的指数值一致。我们证明了连续粒子对的标度性质的PCPD是相同的耦合模型中的A物种。这两个物种的图片解决了概念上的困难,种子模拟在原来的PCPD和自然引入多个长度和时间尺度,这导致强烈的校正缩放。从我们的模拟中提取的矩比表明,我们的模型显示出相同的时间交叉行为的PCPD,这进一步证实了它的完整的动力学等效与我们的耦合模型。

英文摘要:

The contact process with diffusion (PCPD) defined by the binary reactions 2 B -> 3 B, 2 B -> 0 and diffusive particle spreading exhibits an unusual active to absorbing phase transition whose universality class has long been disputed. Multiple studies have indicated that an explicit account of particle pair degrees of freedom may be required to properly capture this system's effective long-time, large-scale behavior. We introduce a two-species representation in which single particles B and pairs A are coupled according to the stochastic reactions B + B -> A, A -> A + B, A -> 0, and A -> B + B. Mean-field analysis reveals that the phase transition is driven by competition and balance between both species. We employ Monte Carlo simulations to demonstrate that this model captures the pertinent PCPD features. In the inactive phase, A particles rapidly go extinct, leaving the B species to undergo pure pair annihilation kinetics. At criticality, both A and B densities decay with the same exponents as the PCPD order parameters, and display mean-field scaling above the critical dimension 2. In one dimension, the critical exponents for the B species obtained from seed simulations agree well with previously reported exponent values. We demonstrate that the scaling properties of consecutive particle pairs in the PCPD are identical with that of the A species in the coupled model. This two-species picture resolves the conceptual difficulty for seed simulations in the original PCPD and naturally introduces multiple length and time scales, which cause strong corrections to scaling. The extracted moment ratios from our simulations indicate that our model displays the same temporal crossover behavior as the PCPD, which further corroborates its full dynamical equivalence with our coupled model.

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