Spectral gaps for random Schreier graphs
- đ¤ Speaker: Ewan Cassidy (University of Cambridge)
- đ Date & Time: Wednesday 08 October 2025, 10:15 - 11:15
- đ Venue: Seminar Room 1, Newton Institute
Abstract
I will discuss a generalization of Friedman’s theorem, focusing on the spectral gap of the random regular Schreier graphs associated with the action of S_n on K_n—tuples of distinct elements in {1,...,n}. The proof relies on the `polynomial method’, a new approach to strong convergence of Chen, Garza—Vargas, Tropp and van Handel, combined with new group theoretic inputs. A key ingredient is a new asymptotic bound on the expected character of a random permutation obtained via a word map, which is expressed in terms of the dimension of the corresponding representation.
Series This talk is part of the Isaac Newton Institute Seminar Series series.
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Ewan Cassidy (University of Cambridge)
Wednesday 08 October 2025, 10:15-11:15