Theoretical Physics Seminar: Alessandro Tanzini

Title: Surface defects, Toda equations and BPS spectra

Abstract: We show that the partition functions of 4d supersymmetric gauge theories with 8 supercharges in presence of surface defects obey a non-autonomous version of Toda system and we comment on its M-theory origin. The solution to the corresponding equations provides new recursion relations allowing for instanton counting for all simple groups from A to E. The uplift to 5d is a discrete flow generated by automorphisms of the associated BPS quiver. We show that for a class of theories, the 4d reduction of these discrete flows displays an intriguing new relation with Argyres-Douglas SCFTs.