Videos

The Distribution of Sandpile Groups of Random Graphs

Presenter
September 29, 2014
Keywords:
  • Extremal Combinatorics
MSC:
  • 05Dxx
Abstract
We determine the distribution of the sandpile group (a.k.a. Jacobian) of the Erdős–Rényi random graph G(n,q) as n goes to infinity. Since any particular abelian group appears with asymptotic probability 0 (as we show), it is natural ask for the asymptotic distribution of Sylow p-subgroups of sandpile groups. We prove the distributions of Sylow p-subgroups converge to specific distributions conjectured by Clancy, Leake, and Payne. These distributions are related to, but different from, the Cohen-Lenstra distribution. Our proof involves first finding the expected number of surjections from the sandpile group to any finite abelian group (the "moments" of a random variable valued in finite abelian groups). To achieve this, we show a universality result for the moments of cokernels of random symmetric integral matrices that is strong enough to handle dependence in the diagonal entries. We then show these moments determine a unique distribution despite their p^{k^2}-size growth.