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arXiv math/0402156math.PR
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无界类型分支过程的临界性

Criticality in unbounded-types branching processes

G. T. Tetzlaff

摘要:

研究了离散时间分支过程的几乎必然灭绝的条件。没有假设期望的子节点数是父节点类型的有界函数。也可能不存在整数m,使得种群在第m代灭绝的概率存在一个正下界,在祖先的类型上是一致的。一个比存在这样一个m更弱的条件被认为是导致灭绝几乎肯定,如果预期的世代大小的序列不趋于无穷大。给出了不绝灭概率为正的一些判据。通过扩展到我们的设置两个应用程序,即莱斯利人口动态和连续渗流中产生的过程中,后代遵循泊松点分布的例子。

英文摘要:

Conditions for almost sure extinction are studied in discrete time branching processes with an infinite number of types. It is not assumed that the expected number of children is a bounded function of the parent's type. There might also be no integer m such that there is a lower positive bound, uniform over the ancestor's type, for the probability that a population is extinct at the m-th generation. A weaker condition than the existence of such an m is seen to lead to extinction almost surely if the sequence of expected generation sizes does not tend to infinity. Some criteria for a positive probability of nonextinction are given. Examples are provided by extending to our setting two applications, namely Leslie population dynamics and processes arising in continuum percolation in which the offsprings follow Poisson point distributions.

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