Nonlinear Supersymmetry Without the GSO Projection and Unstable D9-Brane

TL;DR

This paper investigates the nonlinear N=2 supersymmetry in orientable open string theories without GSO projection, confirming low-energy theorems for 4-fermion amplitudes and exploring the link to open-open string duality.

Contribution

It provides the first explicit confirmation of low-energy theorems for non-GSO projected open strings and reveals a connection between hidden supersymmetry and string duality.

Findings

4-fermion amplitudes obey low-energy theorems

Hidden supersymmetry relates to open-open string duality

Confirmed nonlinear N=2 supersymmetry in unstable D9-brane context

Abstract

Orientable open string theories containing both bosons and fermions without the GSO projection are expected to have the 10 dimensional N=2(A) space-time supersymmetry in a spontaneously broken phase. We study the low-energy theorem for the nonlinearly realized N=2 supersymmetry using the effective action for an unstable D9-brane. It is explicitly confirmed that the 4-fermion open string amplitudes without the GSO projection obey the low-energy theorem derived from the nonlinear N=2 supersymmetry. An intimate connection between the existence of the hidden supersymmetry and the open-open string (s-t) duality is pointed out.