Linear Growth for Greedy Lattice Animals
Abstract
Let $d\geq 2$, and let ${X_\bv, \bv\in\ZZ^d$ be an i.i.d.\ family of non-negative random variables with common distribution $F$. Let $N(n)$ be the maximum value of $\sum_\bv\in\xiX_\bv$ over all connected subsets $\xi$ of $\ZZ^d$ of size $n$ which contain the origin. This model of «greedy lattice animals» was introduced by Cox et al.\ (1993) and Gandolfi and Kesten (1994), who showed that if $î X_\bzero^d (\log^+ X_\bzero)^d+\epsilon<\infty$ for some $\epsilon>0$, then $N(n)/n\to N$ a.s.\ and in $\cL_1$ for some $N<\infty$. Using related but partly simpler methods, we derive the same conclusion under the slightly weaker condition that $\int_0^\infty- \big(1-F(x)\big)^1/ddx<\infty$, and show that $N\leq c\int_0^\infty\big(1-F-(x)\big)^1/ddx$ for some constant $c$. We also give analogous results for the related «greedy lattice paths» model.