Exact semiclassical and nonperturbative BPS spectra in N = 2 susy QCD
Abstract
These notes are based on work done in collaboration with Frank Ferrari. We show how to determine the spectra of stable BPS states in N = 2 supersymmetric SU (2) YangMills theories that are asymptotically free, i.e. without and with N_{f} = 1, 2, 3 quark hypermultiplets. In all cases: ∙ There is a curve of marginal stability diffeomorphic to a circle and going through all (finite) singular points of moduli space.
∙ The BPS spectra are discontinuous across the curves.
∙ The strongcoupling spectra (inside the curves) contain only those BPS states that can become massless and are responsible for the singularities. Except for N_{f} = 3, they form a multiplet (with different masses) of the broken global discrete symmetry.
∙ All other semiclassical BPS states must and do decay consistently when crossing the curves.
∙ The weakcoupling, i.e. semiclassical BPS spectra, contain no magnetic charges larger than one for N_{f} = 0, 1, 2 and no magnetic charges larger than two for N_{f} = 3.
 Publication:

Nuclear Physics B Proceedings Supplements
 Pub Date:
 July 1997
 DOI:
 10.1016/S09205632(97)003277
 Bibcode:
 1997NuPhS..56..199B