Title
Dense subgroups of automorphism groups of homogeneous countable structures
Abstract
Given a Polish group G (for us, the automorphism group of a countable homogeneous structure), it is interesting to understand which countable groups are isomorphic to a dense subgroup of G; and to what extent this class of groups characterizes G (a question which seems largely unexplored at the moment). I will discuss some facts related to these questions, focusing on automorphism groups of countable Urysohn spaces (an infinite set and the random graph are already interesting examples). The talk will be based on two papers: on joint with P. Fima, F. Le Maître and S. Moon, the other joint with M. Etedadialiabadi, S. Gao, and F. Le Maître.
Access to the event
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