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arXiv 1208.0306math.PR
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随机环境中分支随机游动的矩渐近性

Moment asymptotics for branching random walks in random environment

Onur Gün, Wolfgang König, Ozren Sekulović

摘要:

研究了格点$\Z^d$上随机环境中分支随机游动的长时间行为。粒子的迁移根据连续时间内的简单随机游走进行,而介质作为空间依赖性杀伤/分支率的随机势给出。我们感兴趣的主要对象是退火矩$< m_n^p > $,即,局部和全局种群大小的迁移和杀死/分支的$p$阶矩在$n$阶矩的介质上。对于$n=1$,这是很好理解的\cite{GM98},因为$m_1$与抛物线安德森模型密切相关。对于某些特殊的分布,\cite{A00}将其扩展到$n\geq2$,但仅限于渐近的第一项,使用$m_n$的Feynman-Kac公式(递归版本)。在这项工作中,我们也推导出第二项的渐近,为一个更大的类的分布。特别是,我们表明,$< m_n^p >$和$< m_1^{np} >$是渐近相等的,错误$\e^{o(t)}$。我们的方法的基石是一个直接的Feynman-Kac型公式$m_n$,我们建立使用\cite{HR11}开发的脊柱技术。

英文摘要:

We consider the long-time behaviour of a branching random walk in random environment on the lattice $\Z^d$. The migration of particles proceeds according to simple random walk in continuous time, while the medium is given as a random potential of spatially dependent killing/branching rates. The main objects of our interest are the annealed moments $< m_n^p > $, i.e., the $p$-th moments over the medium of the $n$-th moment over the migration and killing/branching, of the local and global population sizes. For $n=1$, this is well-understood \cite{GM98}, as $m_1$ is closely connected with the parabolic Anderson model. For some special distributions, \cite{A00} extended this to $n\geq2$, but only as to the first term of the asymptotics, using (a recursive version of) a Feynman-Kac formula for $m_n$. In this work we derive also the second term of the asymptotics, for a much larger class of distributions. In particular, we show that $< m_n^p >$ and $< m_1^{np} >$ are asymptotically equal, up to an error $\e^{o(t)}$. The cornerstone of our method is a direct Feynman-Kac-type formula for $m_n$, which we establish using the spine techniques developed in \cite{HR11}.

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