Maximum displacement of critical centered branching random walks under minimal assumptions

Abstract

We study the critical centered branching random walk with offspring and displacement distributions having finite variance, under minimal assumptions on its structure. We show that the probability that the position of the right-most particle is larger than $r$ decays like an explicit constant times $r^{-2}$; this generalizes an earlier result by Lalley and Shao. In addition, we obtain the convergence in distribution of the progeny of the branching random walk conditioned on the position of the right-most particle being large. Our results are applied to multitype branching random walks under minimal assumptions.