IS13: Recent Developments in Branching Structures

Organizer: Sarah Penington (University of Bath)

Sharp LlogL condition for supercritical Galton-Watson processes with countable types

Mathilde André

We investigate Kesten–Stigum-like results for multi-type Galton–Watson processes with a countable number of types in a general setting, allowing us in particular to consider processes with an infinite total population at each generation. Specifically, a sharp \(L\log L\) condition is found under the only assumption that the mean reproduction matrix is positive recurrent in the sense of \([1]\). The type distribution is shown to always converge in probability in the recurrent case, and under conditions covering many cases it is shown to converge almost surely.

This is a joint work with Jean-Jil Duchamps (Université de Franche-Comté).

Bibliography

\([1]\) Vere-Jones, D. (1967) Ergodic properties of nonnegative matrices. I. Pacific Journal of Mathematics, 22(2):361–386.