BPS spectra of dyons in four-dimensional N=2 supersymmetric theories

Analysing the kinematics and monodromies around singularities in quantum mo duli space of four-dimensional N = 2 supersymmetric theory without as well as with hypermultiplets, spectra of BPS states have been obtained separatel y in weak and strong coupling regions. It has been shown that in the absenc e of hypermultiplets, the weak coupling spectrum contains all dyons with in tegral electric charges and unit magnetic charge, while the strong coupling spectrum consists of only the particles responsible for the monodromies at singularities. Demonstrating electric-magnetic flavour duality in the pres ence of supermultiplets with non-zero bare masses, it has been shown that i n the presence of a single flavour, the Coulomb branch of moduli space exhi bits Z(3)-symmetry with dyonic states of single unit of magnetic charge exi sting in the weak and strong coupling regions. It has also been shown that the strong coupling spectrum, in the presence of two flavours, consists of one Z(2)-pair and that, in the presence of three flavours, it consists of d yons with one and two units of magnetic charge.