UW Combinatorics Talk

UW Combinatorics Seminar

Title: Counting in Thompson's group F - enumeration and experimentation

Andrew Rechnitzer

University of British Columbia

December 7, 4:00pm
Padelford C-401

refreshments at 3:30pm
Pre-Seminar at 2:30pm in Padelford C-401

ABSTRACT 

Richard Thompson's group F is a widely studied group which has provided examples of and counter-examples to a variety of conjectures in group theory. It is also an extremely combinatorially appealing object which has a beautiful description in terms of binary trees. In this talk I will describe two important enumerative problems associated with F. The first is the problem of computing the growth-series of F - the number of elements with geodesic length n. I will describe the polynomial time algorithm that "solves" the problem and a couple of associated conjectures. The second problem is the cogrowth series - the number of words of length n equivalent to the identity. This second problem important because of its connections to the amenability of F and I will describe some of our recent experimental explorations of this problem using techniques from enumeration and statistical mechanics.


Speaker's Contact Info: http://www.math.ubc.ca/~andrewr/


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Sara Billey, Combinatorics Seminar, Mathematics Department, University of Washington,

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