Pietro Longhi (Uppsala U.), “BPS Graphs of Class S Theories”

Seminar Organizer

Event Details

ABSTRACT: BPS quivers and Spectral Networks are two powerful tools for computing BPS spectra in 4d N=2 theories. On the Coulomb branches of these theories, the BPS spectrum is well-defined only away from walls of marginal stability, where wall-crossing phenomena take place.
Surprisingly, while BPS spectra are ill-defined, there is a lot of information hidden in spectral networks at maximal intersections of MS walls. In this talk I will describe how they give rise to BPS graphs, and how the relation of the latter to BPS quivers emerges naturally. I will also present a novel construction of the wall-crossing invariant of Kontsevich and Soibelman, a.k.a the BPS monodromy, based entirely on topological data of BPS graphs, and derived by wall-crossing in presence of surface defects.