Vertex operator algebras (VOAs) and their modules define sheaves of conformal blocks over the moduli space of stable curves, generalizing sheaves of conformal blocks attached to Lie algebras. In this talk I will discuss how these sheaves are constructed and which properties they satisfy. I will in particular describe conditions that guarantee that these sheaves are actually vector bundles of finite rank and related open questions. This is based on a joint work with A. Gibney, N. Tarasca and D. Krashen.

I will explain something of the theory of homogeneous Einstein metrics and why certain generalizations of this equation occur naturally in the study of homogeneous spaces.

It is well-known that on a non-projective complex manifold, a
coherent sheaf may not have a resolution by a complex of holomorphic vector
bundles. Nevertheless, J. Block showed that such resolution always exists if
we allow anti-holomorphic flat superconnections which generalize complexes
of holomorphic vector bundles. Block's result makes it possible to study
coherent sheaves with differential geometric and analytic tools. For
example, in a joint work with J.M Bismut, S, Shen, and I, we give an
analytic proof of the Grothendieck-Riemann-Roch theorem for coherent sheaves
on complex manifolds. In this talk I will present the ideas and applications
of anti-holomorphic flat superconnections. I will also talk about analogous
constructions of superconnections in other areas of geometry.

There is a generalization of Lie theory from Lie algebras to differential graded Lie algebras. Ordinary Lie theory involves first order ordinary differential equations. Higher Lie theory may be understood as a non-linear generalization of the de Rham theorem on simplicial complexes (in Dupont's formulation), as against graphs. In this talk, we present an alternate approach to this theory, using the more elementary de Rham theorem on cubical complexes.

Along the way, we will need an interesting relationship between cubical and simplicial complexes, which has recently become better known due to its use in Lurie's theory of straightening for infinity categories.

Gravitational instantons are defined as non-compact hyperKahler
4-manifolds with L^2 curvature decay. They are all bubbling limits of K3
surfaces and thus serve as stepping stones for understanding the K3 metrics.
In this talk, we will focus on a special kind of them called
ALH*-gravitational instantons. We will explain the Torelli theorem, describe
their moduli spaces and some partial compactifications of the moduli spaces.
This talk is based on joint works with T. Collins, A. Jacob, R. Takahashi,
X. Zhu and S. Soundararajan.

Earlier time and joint seminar with Differential Geometry Seminar.