{ "id": "math/0112029", "version": "v1", "published": "2001-12-04T01:49:44.000Z", "updated": "2001-12-04T01:49:44.000Z", "title": "The diameter of a long range percolation graph", "authors": [ "Don Coppersmith", "David Gamarnik", "Maxim Sviridenko" ], "comment": "To appear in Symposium on Discrete Algorithms, 2002", "categories": [ "math.PR", "math-ph", "math.CO", "math.MP" ], "abstract": "We consider the following long range percolation model: an undirected graph with the node set $\\{0,1,...,N\\}^d$, has edges $(\\x,\\y)$ selected with probability $\\approx \\beta/||\\x-\\y||^s$ if $||\\x-\\y||>1$, and with probability 1 if $||\\x-\\y||=1$, for some parameters $\\beta,s>0$. This model was introduced by Benjamini and Berger, who obtained bounds on the diameter of this graph for the one-dimensional case $d=1$ and for various values of $s$, but left cases $s=1,2$ open. We show that, with high probability, the diameter of this graph is $\\Theta(\\log N/\\log\\log N)$ when $s=d$, and, for some constants $0<\\eta_1<\\eta_2<1$, it is at most $N^{\\eta_2}$, when $s=2d$ and is at least $N^{\\eta_1}$ when $d=1,s=2,\\beta<1$ or $s>2d$. We also provide a simple proof that the diameter is at most $\\log^{O(1)}N$ with high probability, when $d