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arXiv 0902.4762math.PRmath.CO
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相互作用扩散的组合分析

A combinatorial analysis of interacting diffusions

Sourav Chatterjee, Soumik Pal

摘要:

我们考虑一类特殊的n维齐次扩散,所有这些都有一个单位扩散矩阵和漂移函数,是分段常数和尺度不变。抽象的随机分析立即给我们一般性的结果存在性和唯一性的法律和不变的概率分布时,他们的存在。这些不变分布是$n$维空间上的概率测度,并且可能非常难以更详细地理解。为了有一个更好的分析,我们构建了一个多面体,使其表面的向内法线由漂移函数给出,并表明不变的概率测度的精细结构与多面体的几何形状交织在一起。我们表明,几个自然相互作用的布朗粒子模型,从而可以分析通过研究组合风扇产生的漂移函数,特别是当这些是单纯的。这是当多面体是一个多面体,是不变的考克斯特组的作用下,这导致了一个明确的描述的不变测度在iid指数随机变量。另一类例子是由加权图索引的相互作用提供的,所有这些图都生成具有$n !$面的单纯多面体。我们发现,在每个组件单形中包含的体积的比例对应于一个概率分布的置换组,其中一些有令人惊讶的连接与经典的瓮模型。

英文摘要:

We consider a particular class of n-dimensional homogeneous diffusions all of which have an identity diffusion matrix and a drift function that is piecewise constant and scale invariant. Abstract stochastic calculus immediately gives us general results about existence and uniqueness in law and invariant probability distributions when they exist. These invariant distributions are probability measures on the $n$-dimensional space and can be extremely resistant to a more detailed understanding. To have a better analysis, we construct a polyhedra such that the inward normal at its surface is given by the drift function and show that the finer structures of the invariant probability measure is intertwined with the geometry of the polyhedra. We show that several natural interacting Brownian particle models can thus be analyzed by studying the combinatorial fan generated by the drift function, particularly when these are simplicial. This is the case when the polyhedra is a polytope that is invariant under a Coxeter group action, which leads to an explicit description of the invariant measures in terms of iid Exponential random variables. Another class of examples is furnished by interactions indexed by weighted graphs all of which generate simplicial polytopes with $n !$ faces. We show that the proportion of volume contained in each component simplex corresponds to a probability distribution on the group of permutations, some of which have surprising connections with the classical urn models.

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