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arXiv 0909.3642math.PR
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可交换分拆与随机离散分布的删除性质刻画

Characterizations of exchangeable partitions and random discrete distributions by deletion properties

Alexander Gnedin, Chris Haulk, Jim Pitman

摘要:

我们证明了一个长期存在的猜想,它描述了Ewens-Pitman双参数可交换随机划分族,加上一个简短的极限和例外情况列表,通过以下性质:对于每个$n = 2,3, >...$,如果随机均匀地选择$n$个体之一,而与这些个体随机划分为各种类型的$π_n$无关,并且删除与所选个体相同类型的所有个体,然后对于每个$r > 0$,假定保留$r$个体,根据$π_r'$将这些个体划分为不依赖于$n$的随机划分$(π_r')$的某个序列。一个类似的结果表征了相关的Poisson-Dirichlet族的随机离散分布的独立性有关的随机删除的频率选择的大小偏置挑选。我们还调查的再生性能的两个参数的家庭的成员,并解决一个问题,关于明确安排的时间间隔的Poisson-Dirichlet随机序列到区间分区的范围内引起的中性到正确的过程。

英文摘要:

We prove a long-standing conjecture which characterises the Ewens-Pitman two-parameter family of exchangeable random partitions, plus a short list of limit and exceptional cases, by the following property: for each $n = 2,3, >...$, if one of $n$ individuals is chosen uniformly at random, independently of the random partition $π_n$ of these individuals into various types, and all individuals of the same type as the chosen individual are deleted, then for each $r > 0$, given that $r$ individuals remain, these individuals are partitioned according to $π_r'$ for some sequence of random partitions $(π_r')$ that does not depend on $n$. An analogous result characterizes the associated Poisson-Dirichlet family of random discrete distributions by an independence property related to random deletion of a frequency chosen by a size-biased pick. We also survey the regenerative properties of members of the two-parameter family, and settle a question regarding the explicit arrangement of intervals with lengths given by the terms of the Poisson-Dirichlet random sequence into the interval partition induced by the range of a neutral-to-the right process.

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