A Refined Count of BPS States in the D1/D5 System

TL;DR

This paper investigates the refined counting of BPS states in the D1/D5 system by analyzing the spectrum of a 2d conformal field theory at different moduli space points, revealing detailed spectral growth and symmetry structures.

Contribution

It provides a detailed analysis of the low-lying BPS spectrum in the D1/D5 system, including refined counts and spectral decompositions at various moduli space points.

Findings

Spectrum growth at symmetric orbifold point

Spectrum growth at supergravity point

Decomposition into $ abla=4$ characters and symmetry insights

Abstract

We examine the low-lying quarter BPS spectrum of a 2d conformal field theory with target Sym$^N(K3)$ at various points in the moduli space, and look at a more refined count than the ordinary elliptic genus. We compute growth of the spectrum at both the symmetric orbifold point, as well as at the supergravity point in the moduli space. Finally we do a decomposition of the spectra into $\mathcal{N}=4$ characters and discuss possible relations to interesting symmetry groups. A similar analysis is done with $T^4$.