论文标题

关键分支布朗尼运动中的集群

Clusters in the critical branching Brownian motion

论文作者

Ferté, Benoît, Doussal, Pierre Le, Rosso, Alberto, Cao, Xiangyu

论文摘要

以相等速度复制和歼灭的布朗颗粒具有很强的相关位置,形成了一些由大间隙隔开的紧凑型簇。我们使用群集的定义在给定时间的定义中表征了粒子的分布,该术语是我们中一些人最近引入的粗粒度长度。我们表明,在未灭绝的实现中,簇的平均数量随着$ \ sim t^{d _ {\ mathrm {f}}/2} $而增长,其中$ d _ {\ m atrm {f}} \大约是0.22 $是超级胸运动的haussdoff dimension the haussdoff dismension ys per ers per&per nik and per nik and per nik y。我们还计算了连续颗粒之间的间隙分布。我们发现两个由特征长度比例$ \ ell = \ sqrt {d/β} $隔开的机制,其中$ d $是扩散常数,而分支率$β$。 $ \ sim g^{d _ {\ mathrm {f}} $ 2} $ for $ g \ \ ll \ ell $和$ \ sim g^{ - D _ {\ sim g^{ - d _ { - d _ {\ mathrm {f}} $ for $ g \ gg gg gg \ ell $。最后,以粒子$ n $的数量为条件,上述分布对$ g \ ll \ sqrt {n} $有效;大于$ g \ gg \ sqrt {n} $的平均间隙数远小于一个,并且衰减为$ \ simeq 4(g/\ sqrt {n})^{ - 2} $,与Ramola,Majumdar,Majumdar和Schehr的通用差距分发一致。我们的结果在密集的超棕色运动状态和大差距方面之间进行了插值,从而统一了两种先前独立的方法。

Brownian particles that are replicated and annihilated at equal rate have strongly correlated positions, forming a few compact clusters separated by large gaps. We characterize the distribution of the particles at a given time, using a definition of clusters in terms a coarse-graining length recently introduced by some of us. We show that, in a non-extinct realization, the average number of clusters grows as $\sim t^{D_{\mathrm{f}}/2}$ where $D_{\mathrm{f}} \approx 0.22$ is the Haussdoff dimension of the boundary of the super-Brownian motion, found by Mueller, Mytnik, and Perkins. We also compute the distribution of gaps between consecutive particles. We find two regimes separated by the characteristic length scale $\ell = \sqrt{D/β}$ where $D$ is the diffusion constant and $β$ the branching rate. The average number of gaps greater than $g$ decays as $\sim g^{D_{\mathrm{f}}-2}$ for $g\ll \ell$ and $\sim g^{-D_{\mathrm{f}}}$ for $g \gg \ell$. Finally, conditioned on the number of particles $n$, the above distributions are valid for $g \ll \sqrt{n}$; the average number of gaps greater than $g \gg \sqrt{n}$ is much less than one, and decays as $\simeq 4 (g/\sqrt{n})^{-2}$, in agreement with the universal gap distribution predicted by Ramola, Majumdar, and Schehr. Our results interpolate between a dense super-Brownian motion regime and a large-gap regime, unifying two previously independent approaches.

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