Ergodic behavior of non-conservative semigroups via generalized Doeblin's conditions

TL;DR

This paper establishes quantitative convergence estimates for non-conservative, non-homogeneous positive semigroups using generalized Doeblin's conditions, with applications to population dynamics and PDEs.

Contribution

It introduces a novel approach combining conservative semigroups and Doeblin's conditions to analyze ergodic behavior of complex non-conservative systems.

Findings

Quantitative total variation estimates for positive semigroups.

Asymptotic profiles for growth diffusion models.

Convergence speed bounds for periodic semigroups.

Abstract

We provide quantitative estimates in total variation distance for positive semi-groups, which can be non-conservative and non-homogeneous. The techniques relies on a family of conservative semigroups that describes a typical particle and Doeblin's type conditions for coupling the associated process. Our aim is to provide quantitative estimates for linear partial differential equations and we develop several applications for population dynamics in varying environment. We start with the asymptotic profile for a growth diffusion model with time and space non-homogeneity. Moreover we provide general estimates for semigroups which become asymptotically homogeneous, which are applied to an age-structured population model. Finally, we obtain a speed of convergence for periodic semi-groups and new bounds in the homogeneous setting. They are are illustrated on the renewal equation.