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NYGT Spring Seminar Feb 24: Benjamin Steinberg, CCNY/CUNY

posted Feb 17, 2012, 8:45 AM by Office Manager   [ updated Feb 17, 2012, 8:46 AM ]
Benjamin Steinberg of The City College of New York/CUNY will speak at the New York Group Theory Spring Seminar on February 24, 2012.  His talk will begin at 4pm in Room 5417.  Join us for tea and cookies at 3:30pm in the the Mathematics Lounge on the 4th floor.

Measure-theoretic aspects of boundary actions of groups on regular rooted trees

We survey some results concerning measure theoretic aspects of
spherically transitive actions of groups on regular rooted trees, in
particular focusing on automaton groups.  In particular, we present a
result obtained jointly with Kambites and Silva characterizing when
the action ion the boundary is essentially free in terms of the KNS
spectral measure introduced by Grigorchuk and Zuk as well as a
refinement of our result due to Miklos Abert. For groups of finite
state automorphisms we showed that essential freeness  boils down to a
topological condition.  We also discuss a recent result obtained
jointly with Mariya and Yaroslav Vorobets on the essential freeness of
actions of bireversible automaton groups.  All known realizations of
free groups as automaton groups are via bireversible automata.  We
discuss connections of these results with Schreier graphs of the level
actions exhibiting a spectral gap.

New York Group Theory Spring 2012 Seminar
CUNY Graduate Center, 365 Fifth Avenue at 34th Street, Room 5417