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
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.
|Sidansvarig: Filip Lindskog