Speed of extinction for continuous state branching processes in a weakly subcritical L\'evy environment

TL;DR

This paper investigates the extinction speed of continuous state branching processes in weakly subcritical Lévy environments, extending previous work to more general branching mechanisms with regular variation.

Contribution

It introduces a new analysis for the extinction speed under general regularly varying branching mechanisms, broadening the scope beyond stable mechanisms.

Findings

Extended results to general regularly varying branching mechanisms.

Provided asymptotic behavior of extinction times.

Connected process dynamics with Lévy process fluctuation theory.

Abstract

In this manuscript, we continue with the systematic study of the speed of extinction of continuous state branching processes in L\'evy environments under more general branching mechanisms. Here, we deal with the weakly subcritical regime under the assumption that the branching mechanism is regularly varying. We extend recent results of Li and Xu [14] and Palau et al. [17], where it is assumed that the branching mechanism is stable and complement the recent articles of Bansaye et al. [2] and by the authors in [7], where the critical and the strongly and intermediate subcritical cases were treated, respectively. Our methodology combines a path analysis of the branching process together with its L\'evy environment, fluctuation theory for L\'evy processes and the asymptotic behaviour of exponential functionals of L\'evy processes. Our approach is inspired by Afanasyev et al. [1], where the discrete analogue was obtained, and by [2] and [7].