Tid: 12 oktober 2009 kl 15.15-16.30

Plats : Seminarierummet 3733, Institutionen för matematik, KTH, Lindstedts väg 25, plan 7. Karta!

Föredragshållare: Michael Björklund

Titel: The ergodic theory of sumsets

Abstract

Additive combinatorics is concerned with the structure of sumsets in countable abelian groups. In this talk I will try to sketch a recent approach to problems in additive combinatorics via ergodic theory. Our main result is an estimate of the size of the sum of two sets in a countable abelian group when one of the sets is open in the Bohr topology, along with sharp characterizations of the end cases. The proofs demand a very good understanding of return time ergodic theorems in the spirit of Bourgain.

Joint work with A. Fish.

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