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arXiv 1107.0655math.PR
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Lévy过程的指数泛函的扩张因子分解

Extended Factorizations of Exponential Functionals of Lévy Processes

Pierre Patie, Mladen Savov

摘要:

在文献[16]中,在较弱的条件下,得到了正常Lévy过程的指数泛函的Wiener-Hopf型分解.在本文中,我们通过放松有限矩假设以及考虑指数泛函的killed Lévy过程,扩展了这种分解。作为一个副产品,我们得到了一些有趣的新的分布性质享有的一大类这个随机变量,如绝对连续的分布和光滑性,有界性或完全单调的密度。这类结果然后被用来获得类似的性质的法律的最大值和首次通过时间的一些稳定的Lévy过程。因此,例如,我们表明,对于一大类稳定的过程的第一次穿越时间有一个有界的和非递增的密度上的正半线。我们还产生了许多情况下,积分或幂级数表示的法律的指数功能的Lévy过程与单侧或双侧跳跃。我们的主要结果的证明需要与[16]中所开发的不同的设备。它特别依赖于最近在[8]中引入的一个变换的推广以及Wiener-Hopf技术的Killed Lévy过程的一些扩展。

英文摘要:

In [16], under mild conditions, a Wiener-Hopf type factorization is derived for the exponential functional of proper Lévy processes. In this paper, we extend this factorization by relaxing a finite moment assumption as well as by considering the exponential functional for killed Lévy processes. As a by-product, we derive some interesting new distributional properties enjoyed by a large class of this random variable, such as the absolute continuity of its distribution and the smoothness, boundedness or complete monotonicity of its density. This type of results is then used to derive similar properties for the law of maxima and first passage time of some stable Lévy processes. Thus, for example, we show that for a large class of stable processes the first passage time has a bounded and non-increasing density on the positive half-line. We also generate many instances of integral or power series representations for the law of the exponential functional of Lévy processes with one or two-sided jumps. The proof of our main results requires different devices from the one developed in [16]. It relies in particular on a generalization of a transform recently introduced in [8] together with some extensions to killed Lévy process of Wiener-Hopf techniques.

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