Chennai Mathematical Institute


2.15 p.m.
Mathieu Moonshine from counting dyonic states in string theory

Suresh Govindarajan
IIT Madras.


Four-dimensional N=4 string theories have provided us with examples where the Bekenstein-Hawking entropy of dyonically charged black holes can be understood in terms of the degeneracy of microstates carrying the same charges. The sporadic Mathieu group, M_24, made a somewhat mysterious appearance in counting problems associated with these examples. We will see that it leads to a moonshine for two Mathieu groups, M_24 as well as M_12, that relates their conjugacy classes to modular forms as well as Borcherds-Kac-Moody Lie superalgebras.