11 April 2016 to 15 July 2016
Institut Henri Poincaré
Europe/Paris timezone


Sameer Murthy, King's College

Title: Single-centered black hole degeneracies from brane-instantons

Abstract: I shall begin by reviewing the computation of exact black hole entropy using localization in supergravity. I shall then discuss how to include the effects of string worldsheet instantons in the effective action of N=4 supergravity. This leads to a formula consisting of a sum over Bessel functions with successively sub-leading arguments, as in the Rademacher expansion of Jacobi forms -- but begins to disagree with such a structure near an order where the single-centered nature of the black hole becomes relevant. This leads to a systematic method to recover the polar terms of the microscopic black hole degeneracies from the degeneracy of instantons (the Gromov-Witten invariants). The formula can be checked explicitly against expressions for the microscopic BPS counting functions that are known in terms of certain mock modular forms. 

Your browser is out of date!

Update your browser to view this website correctly. Update my browser now