Path decompositions for real Levy processes
Abstract
Description
Let $X$ be a real Lévy process and let $\Xpos $ be the process conditioned to stay positive. We assume that $ 0 $ is regular for $(-\infty, 0)$ and $(0, +\infty) $ with respect to $X$. Using elementary excursion theory arguments, we provide a simple probabilistic description of the reversed paths of $X$ and $\Xpos $ at their first hitting time of $ (x, +\infty)$ and last passage time of $ (-\infty, x ] $, on a fixed time interval $[0, t]$, for a positive level $x$. From these reversion formulas, we derive an extension to general Lévy processes of Williams' decomposition theorems, Bismut's decomposition of the excursion above the infimum and also several relations involving the reversed excursion under the maximum.
30 pages
30 pages