SL(2, Z) duality and magnetically charged strings

Abstract

The postulate of SL(2, Z) invariance of toroidally compactified heterotic string theory in four dimensions implies the existence of new string (dual string) states carrying both electric and magnetic charges. In this paper we study the interaction between these dual strings. In particular, we consider the scattering of two such strings in the limit where one string passes through the other string without touching it, and show that such scattering leads to the exchange of a fixed amount of electric and magnetic charge between the two strings.