It is well-known that the expected scaled maximum of non-negative random variables with unit mean defines a stable tail dependence function associated with some extreme-value copula. In the special case when these random variables are independent and identically distributed, min-stable multivariate exponential random vectors with the associated survival extreme-value copulas are shown to arise as finite-dimensional margins of an infinite exchangeable sequence in the sense of De Finetti's Theorem. The associated latent factor is a stochastic process which is strongly infinitely divisible with respect to time, which induces a bijection from the set of distribution functions F of non-negative random variables with finite mean to the set of L\'evy measures on the positive half-axis. Since the Gumbel and the Galambos copula are the most popular examples of this construction, the investigation of this bijection contributes to a further understanding of their well-known analytical similarities. Furthermore, a simulation algorithm based on the latent factor representation is developed, if the support of F is bounded. Especially in large dimensions, this algorithm is efficient because it makes use of the De Finetti structure.
翻译:众所周知, 非负随机变量的预期最大比例,其单位值将定义一个与某些极值相伴的稳定的尾部依赖性功能。在特例中,当这些随机变量是独立且分布相同的时,与相关生存的极端值相伴的多色多变随机矢量,被证明是De Finetti的理论意义中无限互换序列的有限边际。相关的潜在因素是一个随机过程,在时间上可以明显地无限地变异,它从分布函数F中引出非负随机变量F的比方,对正值半轴的L\'evy计量具有一定的平均值。由于Gumbel和Galambos coula是这一构造中最受欢迎的例子,因此对这一双选点的调查有助于进一步了解它们众所周知的分析相似性。此外,如果F的支持被捆绑,则基于潜在要素的模拟算法,则会发展出一个基于潜值的模拟算法。特别是大维度,这一算法是有效的,因为它使用了Simtti的架构。