Conditional Path Decomposition at the Infimum and Maximum Drawdowns for Spectrally Negative Lévy Processes

Abstract

We study maximum-drawdown laws conditioned on extremes for a spectrally negative Lévy process and observed up to an independent exponential time. The main contribution is a set of scale-function characterizations of the pre-infimum path arising from two decompositions of the process. The first is the decomposition at the infimum into pre-infimum and post-infimum components. The second, under the ordering in which the infimum is attained before the supremum, decomposes the path into pre-infimum, intermediate, and post-supremum components. We also identify the distribution of the supremum for the pre-infimum process in the first decomposition. The resulting conditional laws are expressed as Doob $h$-transforms of killed spectrally negative Lévy processes and they yield explicit formulas for the maximum drawdown on each independent path component. The results confirm the classical decompositions for Brownian motion.