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arXiv 0709.0773math.PR
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粒子系统占据时间的高密度极限引起的自相似稳定过程

Self-similar stable processes arising from high-density limits of occupation times of particle systems

Tomasz Bojdecki, Luis G. Gorostiza, Anna Talarczyk

摘要:

推广了Poisson初始条件下$(d,α, β)$ -分支粒子系统$(0<α\leq 2, 0<β\leq 1)$的时间尺度占据时间涨落极限的结果.在均匀情况下的早期结果(即,Lebesgue初始强度测量)仅针对维度$d>α/ β$获得,因为如果$d\le α/ β$,则粒子系统变得局部灭绝。本文通过引入初始Poisson组态的高密度,得到了所有维数的极限,并且当$d>α/β$满足时,它们与以前的结果一致.我们还给出了有限强度测度系统的高密度极限(没有高密度,在这种情况下由于消光不存在极限);由于粒子运动测度的非不变性,结果是不同的,更难获得。在这两种情况下,即,Lebesgue和有限强度测度,对于低维(分别为$d<α(1+β)/β$和$d<α(2+β)/(1+β)$),极限由非Lévy自相似稳定过程确定。对于相应的高维,极限性质不同:在勒贝格情形下是${\cal S}'(R^d)$ -值Lévy过程,在有限测度情形下是$(0,\infty)$上时间常数的稳定过程。对于高维,所有极限过程的定律都用Riesz势表示。如果为$β=1$,则限值为高斯限值。限制也给出了粒子系统没有分支,特别是加权分数布朗运动在低维。所得结果是在S '(R^d)$-值过程弱收敛的条件下得到的.

英文摘要:

We extend results on time-rescaled occupation time fluctuation limits of the $(d,α, β)$-branching particle system $(0<α\leq 2, 0<β\leq 1)$ with Poisson initial condition. The earlier results in the homogeneous case (i.e., with Lebesgue initial intensity measure) were obtained for dimensions $d>α/ β$ only, since the particle system becomes locally extinct if $d\le α/ β$. In this paper we show that by introducing high density of the initial Poisson configuration, limits are obtained for all dimensions, and they coincide with the previous ones if $d>α/β$. We also give high-density limits for the systems with finite intensity measures (without high density no limits exist in this case due to extinction); the results are different and harder to obtain due to the non-invariance of the measure for the particle motion. In both cases, i.e., Lebesgue and finite intensity measures, for low dimensions ($d<α(1+β)/β$ and $d<α(2+β)/(1+β)$, respectively) the limits are determined by non-Lévy self-similar stable processes. For the corresponding high dimensions the limits are qualitatively different: ${\cal S}'(R^d)$-valued Lévy processes in the Lebesgue case, stable processes constant in time on $(0,\infty)$ in the finite measure case. For high dimensions, the laws of all limit processes are expressed in terms of Riesz potentials. If $β=1$, the limits are Gaussian. Limits are also given for particle systems without branching, which yields in particular weighted fractional Brownian motions in low dimensions. The results are obtained in the setup of weak convergence of S'(R^d)$-valued processes.

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