Maximal displacement of spectrally negative branching L\'evy processes

TL;DR

This paper analyzes the maximum displacement in a spectrally negative branching Lévy process, providing asymptotic estimates for the survival function depending on the drift behavior of the underlying Lévy process.

Contribution

It offers new asymptotic estimates for the maximum displacement in spectrally negative branching Lévy processes, distinguishing between critical and subcritical cases.

Findings

Polynomial asymptotics when the Lévy process oscillates or drifts upward.

Exponential asymptotics when the Lévy process drifts downward.

Results depend on the drift direction of the underlying Lévy process.

Abstract

We consider a branching Markov process in continuous time in which the particles evolve independently as spectrally negative L\'evy processes. When the branching mechanism is critical or subcritical, the process will eventually die and we may define its overall maximum, i.e. the maximum location ever reached by a particule. The purpose of this paper is to give asymptotic estimates for the survival function of this maximum. In particular, we show that in the critical case the asymptotics is polynomial when the underlying L\'evy process oscillates or drifts towards $+\infty$, and is exponential when it drifts towards $-\infty$.