Quasidiagonality and amenability

31.01.2018 16:15 - 17:15

Stuart White (University of Glasgow)

In finite dimensions we’re familiar with various canonical forms for matrices, such as diagonalisation or more generally, the Jordan normal form which allows us to present a general matrix in a block diagonal picture.  In infinite dimensions things become more tricky, and exact block diagonal representations of operators on infinite dimensional spaces do not generally exist, though we can look for some kind of approximate block diagonalisation.

This talk will be concerned with one such approximation property: quasidiagonality. Introduced by Halmos in the 70’s it’s has a somewhat mysterious topological flavour, and unexpected connections to other concepts. In this talk I’ll survey quasidiagonality, and explore one such connection — to amenability of groups -- through the so called Rosenberg conjecture.  All terminology in the abstract will be carefully explained during the talk.

Martin Finn-Sell

Sky Lounge, 12. OG, OMP 1