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arXiv 1406.2612cond-mat.stat-mechcond-mat.dis-nn
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周期性相关随机强迫景观中的扩散

Diffusion in periodic, correlated random forcing landscapes

David S. Dean, Shamik Gupta, Gleb Oshanin, Alberto Rosso, Gregory Schehr

摘要:

本文研究了强关联猝灭随机势中布朗粒子的动力学行为,该势定义为任意Hurst指数的分数布朗运动的有限延拓轨迹(具有周期$L$)$H \in (0,1)$ .虽然周期性确保了最终的长时间行为是扩散的,广义西奈潜力考虑在这里导致一个强大的对数约束的粒子轨迹在中间时间。这两个竞争的趋势导致动力学挫折,并导致在丰富的统计行为的扩散系数$D_L$:虽然有典型的值$D^{\rm typ}_L \sim \exp(-βL^H)$,我们表明通过一个精确的分析方法,正的时刻($k>0$)规模像$\langle D^k_L \rangle \sim \exp{[-c' (k βL^{H})^{1/(1+H)}]}$,和负的$\langle D^{-k}_L \rangle \sim \exp(a' (k βL^{H})^2)$,$c'$和$a'$是数值常数和$β$的逆温度。这些结果表明,$D_L$是强非自平均。我们进一步表明,概率分布的$D_L$有一个对数正态的左尾和一个高度奇异的,单侧对数稳定的右尾想起一个Lifshitz奇点。

英文摘要:

We study the dynamics of a Brownian particle in a strongly correlated quenched random potential defined as a periodically-extended (with period $L$) finite trajectory of a fractional Brownian motion with arbitrary Hurst exponent $H \in (0,1)$. While the periodicity ensures that the ultimate long-time behavior is diffusive, the generalised Sinai potential considered here leads to a strong logarithmic confinement of particle trajectories at intermediate times. These two competing trends lead to dynamical frustration and result in a rich statistical behavior of the diffusion coefficient $D_L$: Although one has the typical value $D^{\rm typ}_L \sim \exp(-βL^H)$, we show via an exact analytical approach that the positive moments ($k>0$) scale like $\langle D^k_L \rangle \sim \exp{[-c' (k βL^{H})^{1/(1+H)}]}$, and the negative ones as $\langle D^{-k}_L \rangle \sim \exp(a' (k βL^{H})^2)$, $c'$ and $a'$ being numerical constants and $β$ the inverse temperature. These results demonstrate that $D_L$ is strongly non-self-averaging. We further show that the probability distribution of $D_L$ has a log-normal left tail and a highly singular, one-sided log-stable right tail reminiscent of a Lifshitz singularity.

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