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16.30-17.10, Sal D33, Michael Björklund (KTH):
Entropy of Algebraic Actions of the Discrete Heisenberg Group

**Abstract.**
In 1989, B.Kitchens and K. Schmidt introduced an algebraic approach to
the study
of abelian actions of automorphisms of compact groups. One year
later, D.Lind, T.Ward and
K. Schmidt were able to compute entropy in this new language. In the
case of principal
actions the entropy is given by a logarithmic Mahler measure.
Recently, C. Deninger and K. Schmidt could compute the entropy of
certain non-abelian actions in terms of the Fuglede-
Kadison determinant of the associated von Neumann-algebras. These are
however
notoriously hard to estimate. I will discuss a new approach to get lower
estimates of the entropy
of actions of the discrete Heisenberg group using potential theory.
Joint work with D. Lind.