The sharp threshold for maximum-size sum-free subsets in even-order abelian groups

Abstract

We study sum-free sets in sparse random subsets of even order abelian groups. In particular, we determine the sharp threshold for the following property: the largest such set is contained in some maximum-size sum-free subset of the group. This theorem extends recent work of Balogh, Morris and Samotij, who resolved the case G = Z_{2n}, and who obtained a weaker threshold (up to a constant factor) in general.

29 pages, revised version, to appear in Combinatorics, Probability & Computing