Superstrings in Graviphoton Background and N=1/2+3/2 Supersymmetry

TL;DR

This paper investigates superstrings in a flat space with a graviphoton background, revealing a deformation of supersymmetry algebra and a noncommutative superspace structure on D-branes, contributing to understanding supersymmetry breaking.

Contribution

It introduces a novel analysis of superstrings in a graviphoton background, showing how supersymmetry is partially broken and how noncommutative superspace arises on D-branes.

Findings

Supersymmetry algebra is deformed to include N=1/2 and N=3/2 components.

D-branes preserve a quarter of the original supercharges.

Chiral fermionic coordinates satisfy a Clifford algebra, indicating noncommutative superspace.

Abstract

Motivated by Ooguri and Vafa, we study superstrings in flat R^4 in a constant self-dual graviphoton background. The supergravity equations of motion are satisfied in this background which deforms the N=2 d=4 flat space super-Poincare algebra to another algebra with eight supercharges. A D-brane in this space preserves a quarter of the supercharges; i.e. N=1/2 supersymmetry is realized linearly, and the remaining N=3/2 supersymmetry is realized nonlinearly. The theory on the brane can be described as a theory in noncommutative superspace in which the chiral fermionic coordinates $\theta^\alpha$ of N=1 d=4 superspace are not Grassman variables but satisfy a Clifford algebra.