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arXiv 0704.0380math.PR
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一类分枝扩散的指数增长性

Exponential growth rates in a typed branching diffusion

Y. Git, J. W. Harris, S. C. Harris

摘要:

本文研究了在[Astérisque 236(1996)133 - 154]和[Lecture Notes in Math.1729(2000)239 - 256 Springer,Berlin]中首次研究的一类分支扩散的高温相.主要的目的是建立一些几乎肯定的限制结果的长期行为,这个粒子系统,即速度的人口殖民的空间和类型的维度,以及人口增长的速度在这个渐近形状。我们的方法将包括识别一个明确的两相机制,通过该机制,粒子可以建立在足够的数量与空间位置附近的$-γt$和类型位置附近的$κ\sqrt{t}$在大的时间$t$。证明涉及到各种鞅技术的应用-最重要的是一个“脊柱”建设涉及到一个添加剂鞅措施的变化。除了该模型的内在兴趣,所提出的方法包含的想法,将适应其他分支设置。我们还简要地讨论了相关的反应扩散方程的行波解的应用。

英文摘要:

We study the high temperature phase of a family of typed branching diffusions initially studied in [Astérisque 236 (1996) 133--154] and [Lecture Notes in Math. 1729 (2000) 239--256 Springer, Berlin]. The primary aim is to establish some almost-sure limit results for the long-term behavior of this particle system, namely the speed at which the population of particles colonizes both space and type dimensions, as well as the rate at which the population grows within this asymptotic shape. Our approach will include identification of an explicit two-phase mechanism by which particles can build up in sufficient numbers with spatial positions near $-γt$ and type positions near $κ\sqrt{t}$ at large times $t$. The proofs involve the application of a variety of martingale techniques--most importantly a ``spine'' construction involving a change of measure with an additive martingale. In addition to the model's intrinsic interest, the methodologies presented contain ideas that will adapt to other branching settings. We also briefly discuss applications to traveling wave solutions of an associated reaction--diffusion equation.

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