Fall 2014, Thursdays, Blocker 506A, 4:00-4:50 PM

Date: September 25

"  Mini-Talks

* Weak Huygens' principles and geometry

* One group and three problems "

* Prof. Dean Baskin

* Prof. Rostislav Grigorchuk


D. Baskin: "Weak Huygens' principles and geometry"

: The behavior of waves on manifolds is intimately linked with the underlying geometry. One of the ways they are linked is through various generalized Huygens' principles. In this talk, I will formulate the weak Huygens' principle and explain what it can tell us about geometry. I will also describe some of my recent work (joint with J. Wunsch) on a "very weak" Huygens' principle.

R. Grigorchuk: "One group and three problems"

: I will tell how the group G constructed by the speaker in 1980 solves three famous problems: a (general) Burnside problem (1904), Day's problem on elementary amenability (1957) and Milnor's problem on group growth (1968). The general Burnside problem was already solved in 1964 before the group G was constructed, but G gives the most short and elegant solution to it, and additionally solves two other problems solutions of which were unknown.