Quantization of Dyon Charge and Electric-Magnetic Duality in String Theory

摘要

We analyze the allowed spectrum of electric and magnetic charges carried bydyons in (toroidally compactified) heterotic string theory in four dimensionsat arbitrary values of the string coupling constant and $\theta$ angle. Thespectrum is shown to be invariant under electric-magnetic dualitytransformation, thereby providing support to the conjecture that this is anexact symmetry in string theory.