Student Arithmetic Geometry Seminar: Witt vectors, semirings and total positivity

Seminar | April 7 | 2-3 p.m. | 736 Evans Hall

 Martin Speirs, University of Copenhagen

 Department of Mathematics

The goal of this talk is to explain recent results of James Borger on extending the Witt vector functor from rings to semirings. This is achieved by using various positivity results from the study of symmetric functions. I will introduce a convenient algebraic set-up (introduced by Borger and Wieland under the name of plethories) for dealing with such questions, and finally I will also discuss some examples.