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Geometric Group Theory

GeoGT Session #1.2

Subevent of GeoGT Session #1

Heritage Hall Building 125

Times: 2026 Mar 11 from 10:45AM to 11:05AM (Central Time (US & Canada))

Dense Conjugacy Classes in the Mapping Class Group of Graphs

Rocky Klein <klein@brandeis.edu>, Brandeis University

Abstract:

The mapping class group of a locally finite graph Maps$(X)$ is the set of proper homotopy equivalences of $X$ up to proper homotopy. It is meant to be the analogue of the mapping class group of an infinite-type surface one dimension lower, but it also generalizes Out$(F_n)$ to a much larger class of possibly infinitely generated groups, establishing a “Big Out$(F_n)$.” In this talk, I plan to define the mapping class group for a locally finite graph, discuss its topology, and give motivation. I will then discuss which locally finite graphs $X$ are such that Maps$(X)$ contains a dense conjugacy class. Along the way, we will discuss end spaces and their structures.

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