This series consists of talks in the area of Superstring Theory.
Resent research seems to indicate that charged extremal black holes in D=4 supersymmetric theories should be most naturally described in terms of more primitive atomic constituents. I will briefly describe what I mean by these atomic constituents and how they appear to play a role in both BPS and non-BPS extremal black holes.
It has been known for a long time that instanton effects control the large order behavior of the perturbation series in quantum mechanics and gauge theories. I present a study of this connection in the context of matrix models in 1/N-expansion and topological strings.
I'll discuss a reformulation of twistor-string theory as a heterotic string. This clarifies why conformal supergravity arises and provides a link between the Berkovits and Witten pictures. The talk is based on
arXiv:0708:2276 with Lionel Mason.
I will discuss a solution generating technique that allows to generate
stationary axisymmetric solutions of five-dimensional gravity, starting
from static ones. This technique can be used to add angular momentum
to static configurations. It can also be used to add KK-monopole charge
to asymptotically flat five-dimensional solutions, thus generating geometries
that interpolate between five-dimensional and four-dimensional solutions.