Alladi Ramakrishnan Hall

Applications of moonshine in string compactifications and black holes

Justin R. David

IISc, Bangalore

The discovery of Mathieu moonshine in the elliptic genus
of K3 allows the construction of
twisted elliptic genera to every conjugacy class of the
Mathieu group M23. We show how these twisted elliptic
genera plays play an important role in
both N=2 and N=4 string compactifictions.
In N=2 string compactifications they point to the existence
of a class of Calabi-Yau geometries. In N=4 compactifications
they are inputs to degeneracies of 1/4 BPS states,
which at large values of charges are black holes.
We then study properties of these states at small values
of charges which provide insight to their geometric description
as black holes.