U(1) Charges and Moduli in the D1-D5 System

TL;DR

This paper explores the spectrum of U(1) charged excitations in the D1-D5 system, analyzing how their properties depend on the moduli space and revealing multiple weak-coupling limits connected through strong coupling regions.

Contribution

It provides a detailed analysis of the moduli dependence of charges and entropy in the D1-D5 system, identifying multiple weak-coupling regimes in the conformal field theory.

Findings

Mass formula depends on compactification moduli.

Multiple weak-coupling limits identified for different charge factorizations.

Regions of strong coupling connect different weak-coupling regimes.

Abstract

The decoupling limit of the D1-D5 system compactified on T^4\times S^1 has a rich spectrum of U(1) charged excitations. Even though these states are not BPS in the limit, BPS considerations determine the mass and the semiclassical entropy for a given charge vector. The dependence of the mass formula on the compactification moduli situates the symmetric orbifold Sym^N(T^4) x T^4 conformal field theory in the moduli space. A detailed analysis of the global identifications of the moduli space yields a picture of multiple weak-coupling limits - one for each factorization of N into D1 and D5 charges d1 and d5=N/d1 - joined through regions of strong coupling in the CFT moduli space.