By a celebrated theorem of Coburn, the C*-algebra generated by a proper isometry on Hilbert space is unique, in the sense that it is isomorphic to the C*-algebra generated by any other proper isometry, for example, the unilateral shift on $\ell^2(\mathbb{N})$. In this talk I will consider uniqueness for C*-algebras generated by semigroups of isometries, and discuss how this property is related to the ideal structure of C*-algebras built from actions and partial actions of groups on compact spaces. I will discuss examples arising from number theory and group theory.

16:15 - tea