35, route de Chartres, F-91440 Bures-sur-Yvette (France)
Description
I’ll present a general prescription for the 4d-2d partition function of half-BPS surface defects in d = 4, N = 2 gauge theories in Omega-background which is applicable for any surface defect obtained by gauging a 2d flavour symmetry using a 4d gauge group and reproduces known results obtained via the Higgsing procedure and Kanno-Tachikawa orbifold calculation for Gukov-Witten defects. The role of “negative vortices” which appear in the background of instantons will be emphasized.