Abstract. For positive integers n and d, and the probability function 0 ≤ p(n) ≤ 1, we let Y n,p,d denote the probability space of all at most d-dimensional simplicial complexes on n vertices, which contain the full (d − 1)-dimensional skeleton, and whose d-simplices appear with probability p(n). In this paper we determine the threshold function for vanishing of the top homology group in Y n,p,d , for all d ≥ 1.
Thresholds for vanishing of the (d − 1)st homology group of random d-complexesIn 1959 Erdős and Rényi defined a natural model for random graphs which has since become classical. In this model, which we call 1 Y n,p,1 , the random graph has n vertices, and the edges are chosen uniformly and independently at random with probability p. Usually, one is interested in questions concerning various statistics on this probability space, in the situation when n goes to infinity, and p is a function of n. One of the main results of Erdős-Rényi concerning Y n,p,1 was the discovery of the threshold function for the connectivity of the graph. More precisely, reformulated in our language, they have shown the following theorem.
Theorem 1.1 (Erdős-Rényi Theorem, [4]). Assume that w(n) is any functionw : N → R, such that lim n→∞ w(n) = ∞, and p = p(n) is the probability depending on n. Then we haveMore recently, the two-dimensional analog Y n,p,2 of the Erdős-Rényi model was considered by Linial-Meshulam in [11], and, further, the d-dimensional model Y n,p,d , for d ≥ 3, was considered by Meshulam-Wallach in [13].