Massless BPS-Saturated States on the Two-Torus Moduli Sub-Space of Heterotic String

TL;DR

This paper investigates massless BPS-saturated states in heterotic string theory compactified on a two-torus, identifying charge vectors and supersymmetry preservation conditions at points of gauge symmetry enhancement.

Contribution

It uniquely characterizes the charge vectors of BPS states that become massless at specific moduli space points, detailing their supersymmetry preservation and gauge symmetry enhancement.

Findings

Identifies charge vectors of 1/2 BPS states at gauge enhancement surfaces.

Describes charge vectors of 1/4 BPS states at maximal gauge symmetry points.

Analyzes massless conditions for BPS states in the moduli space.

Abstract

Within a four-dimensional, toroidally compactified heterotic string, we identify (quantized) charge vectors of electrically charged BPS-saturated states (along with the tower of SL(2,Z) related dyonic states), which preserve 1/2 of N=4 supersymmetry and become massless along the hyper-surfaces of enhanced gauge symmetry of the two-torus moduli sub-space. In addition, we identify charge vectors of the dyonic BPS-saturated states (along with the tower of SL(2,Z) related states), which preserve 1/4 of N=4 supersymmetry, and become massless at two points with the maximal gauge symmetry enhancement.