Tail asymptotics for the total progeny of the critical killed branching random walk

Abstract

We consider a branching random walk on $R$ with a killing barrier at zero. At criticality, the process becomes eventually extinct, and the total progeny $Z$ is therefore finite. We show that $P(Z>n)$ is of order $(n\ln^2(n))^{-1}$, which confirms the prediction of Addario-Berry and Broutin [1].