Spontaneously Broken Space-Time Supersymmetry in Open String Theory without GSO Projection

TL;DR

This paper demonstrates that orientable open string theory without GSO projection exhibits spontaneously broken N=2 space-time supersymmetry, supported by formulations in both NS-R and Green-Schwarz frameworks and implications for D-brane stability.

Contribution

It provides the first explicit demonstration of spontaneous supersymmetry breaking in open string theory without GSO projection, including a formal supersymmetry transformation law in string field theory.

Findings

Open string theory without GSO has N=2 supersymmetry in a broken phase.

Supersymmetry transformations are explicitly formulated in string field theory.

Supports the topological approach to stable D-branes from unstable D9-branes.

Abstract

We argue that orientable open string theory without GSO projection has N=2 space-time supersymmetry in a spontaneously broken phase. The arguments are presented both in Neveu-Schwarz-Ramond and Green-Schwarz formulations. The formal but explicit supersymmetry transformation law for string field is given in the framework of Witten's open string field theory. Our results support a fundamental assumption which lies behind the topological construction of stable D-branes starting from the unstable systems of D9-branes.