Sergei Alexandrov, Université de Montpellier
Title: D-instantons, mock modular forms and BPS partition functions
Abstract: I'll discuss the modular properties of D3-brane instantons
appearing in Calabi-Yau string compactifications. I'll show that
the D3-instanton contribution to a certain geometric potential on
the hypermultiplet moduli space can be related to the elliptic
genus of (0,4) SCFT. The modular properties of the potential imply
that the elliptic genus associated with non-primitive divisors
of Calabi-Yau is only mock modular. I'll show how to construct
its modular completion and prove the modular invariance of the
twistorial construction of D-instanton corrected hypermultiplet
moduli space.
