Stable Non-BPS Bound States of BPS D-branes

TL;DR

This paper predicts and calculates the mass of a stable non-BPS state in type IIB string theory on an orbifold, using S-duality symmetry and D-string configurations to identify bound states.

Contribution

It introduces a method to determine the mass of a non-BPS state via D-string pairs and tachyonic mode analysis, confirming the state’s stability.

Findings

Prediction of a stable non-BPS state on an orbifold five plane.

Calculation of the state’s mass through D-string analysis.

Identification of tachyonic modes indicating bound state formation.

Abstract

S-duality symmetry of type IIB string theory predicts the existence of a stable non-BPS state on an orbifold five plane of the type IIB theory if the orbifold group is generated by the simultaneous action of (-1)^{F_L} and the reversal of sign of the four coordinates transverse to the orbifold plane. We calculate the mass of this state by starting from a pair of D-strings carrying the same charge as this state, and then identifying the point in the moduli space where this pair develops a tachyonic mode, signalling the appearance of a bound state of this configuration into the non-BPS state.