The symmetries of a dynamical system \(X\) form an interesting and often
quite complicated group called its automorphism group. A celebrated result
of Boyle, Lind, and Rudolph is that the automorphism group of even very
easily described (but positive entropy) systems frequently contains
isomorphic copies of all of the following (among many others): every finite
group, the free group on two generators, and the direct sum of countably
many copies of \(\mathbb{Z}\). This rich subgroup structure makes it
challenging to find groups that don't embed into \(\mathrm{Aut}(X)\) or
even to prove when two systems have non-isomorphic automorphism groups. By
contrast, a number of strong algebraic results have been obtained in recent
years for symbolic dynamical systems with zero entropy. I will survey a
number of these and discuss recent joint work with B. Kra in which we
obtain strong restrictions on \(\mathrm{Aut}(X)\) for subshifts of
polynomial growth.
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Last modified: April 11 2016 - 18:14:43