Dyon Spectrum in CHL Models
arXiv:hep-th/0510147 · doi:10.1088/1126-6708/2006/04/018
Abstract
We propose a formula for the degeneracy of quarter BPS dyons in a class of CHL models. The formula uses a modular form of a subgroup of the genus two modular group Sp(2,Z). Our proposal is S-duality invariant and reproduces correctly the entropy of a dyonic black hole to first non-leading order for large values of the charges.
LaTeX file, 38 pages, minor changes in section 3.3(v2), minor changes in introduction, appendix A and C(v3)