BPS States of Strings in 3-Form Flux

TL;DR

This paper counts BPS string states in a type IIB flux compactification using supersymmetric quantum mechanics, revealing how flux units influence the spectrum and how orientifolds modify it.

Contribution

It introduces a method to count BPS states in flux backgrounds via supersymmetric quantum mechanics derived from D-brane actions.

Findings

Number of BPS multiplets equals the square of flux units on the torus.

Orientifold projection reduces the number of multiplets by about half.

Provides a pedagogical example with a superparticle on T^2.

Abstract

We count the BPS states of strings in uniform 3-form fluxes, using supersymmetric quantum mechanics derived from the kappa-symmetric action for D-branes. This problem is relevant to the stringy physics of warped compactifications. We work on a type IIB T^6/Z_2 orientifold with imaginary self-dual, quantized, 3-form flux. Ignoring the orientifold projection, the number of short multiplets living on a single string is the square of the units of 3-form flux present on the torus; the orientifold removes roughly half of the multiplets. We review the well-known case of a superparticle on T^2 as an pedagogical example.