Counting dyons in N = 4 string theory

Robbert Dijkgraaf, Erik Verlinde, Herman Verlinde

Research output: Contribution to journalArticlepeer-review

243 Scopus citations


We present a microscopic index formula for the degeneracy of dyons in four-dimensional N = 4 string theory. This counting formula is manifestly symmetric under the duality group, and its asymptotic growth reproduces the macroscopic Bekenstein-Hawking entropy. We give a derivation of this result in terms of the type II five-brane compactified on K3, by assuming that its fluctuations are described by a closed string theory on its world-volume. We find that the degeneracies are given in terms of the denominator of a generalized super Kac-Moody algebra. We also discuss the correspondence of this result with the counting of D-brane states.

Original languageEnglish (US)
Pages (from-to)543-561
Number of pages19
JournalNuclear Physics B
Issue number3
StatePublished - Jan 27 1997

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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