Remarks on BPS bound state “decay”

In N=2 super Yang-Mills theory the charges of a Bogomol’nyi-Prasad-Sommerfield (BPS) state shift under the transition to a dual description of the theory. In particular, in the theory with matter duality, transformations may convert a bound state to an unbound one as predicted by Seiberg and Witten from considerations of the monodromies around the moduli space singularities. The physical mechanism of such behavior on the semiclassical level can be established explicitly through the consideration of soliton-fermion classical field configurations. The problem reduces to the investigation of the fermion spectrum in a slowly varying background monopole field. The behavior of the solutions to classical equations allows one to observe the BPS bound state “decay” in vivo.