Dear all,
Please join us for the following talk on Friday, May 20 at 9AM (Central US time).
Zoom link https://unt.zoom.us/j/83247072014
Speaker: Martin Doležal, The Czech Academy of Sciences
Title: Descriptive complexity of Banach spaces.
Abstract: We introduce a new natural coding of separable Banach spaces. The set of codes consists of (pseudo)norms on a certain vector space and is equipped with a canonical Polish topology. We use this coding to investigate the descriptive complexities of some classical Banach spaces. Among other results, we show that $\ell_2$ is
a) the unique (up to isometry) separable Banach space with a closed isometry class,
b) the unique (up to isomorphism) separable Banach space with an $F_\sigma$ isomorphism class.
This is a joint work with Marek C'uth, Michal Doucha and Ond\v rej Kurka.