[AN] Felix Schwenninger: Spectral constants and Crouzeix's conjecture

21 November 2023 16:00 till 17:00 - Location: EWI-Lecture hall Chip | Add to my calendar

Crouzeix's conjecture postulates that the largest singular value of any polynomial of a complex-square matrix is bounded by 2 times the polynomial's sup-norm taken over the matrix's numerical range.
We review methods to study more general spectral constants through Cauchy integral estimates and discuss recent abstract results which allow for a unified approach to several established results, by exploiting so-called extremal vectors and functions. Joint work with Jens de Vries (Twente).