Strong-Weak Coupling Duality in Four Dimensional String Theory

TL;DR

This paper provides evidence for a strong-weak coupling duality in four-dimensional heterotic string theory, showing it exchanges electric and magnetic states and predicts new stable monopole and dyon states with specific degeneracies.

Contribution

It demonstrates the existence of a strong-weak coupling duality in heterotic string theory, linking it to target space duality and predicting new stable monopole and dyon states.

Findings

Symmetry of low energy effective action under duality

Allowed spectrum of electric and magnetic charges matches duality predictions

Existence of stable monopole and dyon states with specific degeneracies

Abstract

We present several pieces of evidence for strong-weak coupling duality symmetry in the heterotic string theory, compactified on a six dimensional torus. These include symmetry of the 1) low energy effective action, 2) allowed spectrum of electric and magnetic charges in the theory, 3) allowed mass spectrum of particles saturating the Bogomol'nyi bound, and 4) Yukawa couplings between massless neutral particles and massive charged particles saturating the Bogomol'nyi bound. This duality transformation exchanges the electrically charged elementary string excitations with the magnetically charged soliton states in the theory. It is shown that the existence of a strong-weak coupling duality symmetry in four dimensional string theory makes definite prediction about the existence of new stable monopole and dyon states in the theory with specific degeneracies, including certain supersymmetric bound states of monopoles and dyons. The relationship between strong-weak coupling duality transformation in string theory and target space duality transformation in the five-brane theory is also discussed. (Based on a talk given at the workshop on Strings and Gravity, Madras, India.)