Every monotone graph property has a sharp threshold

In their seminal work which initiated random graph theory Erdos and Renyi discovered that many graph properties have sharp thresholds as the number of vertices tends to infinity. We prove a conjecture of Linial that every monotone graph property has a sharp threshold. This follows from the following theorem. Let V-n(p) = {0, 1}(n) denote the Hamming space endowed with the probability measure mu(p) defined by mu(p)(epsilon(1), epsilon(2), ..., epsilon(n)) = p(k) . (1 - p)(n-k), where k = epsilon(1) + epsilon(2) + ... + epsilon(n). Let A be a monotone subset of V-n. We say that A is symmetric if there is a transitive permutation group Gamma on {1, 2,..., n} such that A is invariant under Gamma.