OA/GAMP seminar by Hermann Schulz-Baldes (U Erlangen-Nuernberg)

OA (Operator Algebra)/GAMP (Geometric Analysis and Mathematical Physics) joint seminar

Speaker: Hermann Schulz-Baldes (University of Erlangen-Nuernberg)

Title: Flat bands of surface states via index theory of Toeplitz operators with Besov symbols

Abstract: The scope of the index-theoretic approach to the bulk-boundary correspondence is extended to a pseudo-gap regime. For the case of a half-space graphene model with an edge of arbitrary cutting angle, this allows to express the density of surface as a linear combination of the winding numbers of the bulk. The new technical element is an index theorem for Toeplitz operators with non-commutative symbols from a  Besov space for operators in a finite von Neumann algebra equipped with an R-action. For such operators a type II1 analogue of Peller's traceclass characterization for Toeplitz operators is proved. This is joint work with Tom Stoiber.