We present an index formula that counts the number of dyonic BPS particles of given charges (qe, qm) in four dimensional N = 4 string theory. The formula is invariant under the duality group, and its asymptotic growth matches with the Bekenstein-Hawking entropy. We give a derivation of this result in terms of the type II fivebrane.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Nuclear and High Energy Physics