Understanding moduli spaces is one of the central questions in
algebraic geometry. This talk will survey one of the main aspects of
research in moduli theory — the compactification problem. Roughly speaking,
most naturally occurring moduli spaces are not compact and so the goal is to
come up with geometrically meaningful compactifications. We will begin by
looking at the case of algebraic curves (i.e. Riemann surfaces) and progress
to higher dimensions, where the theory is usually divided into three main
categories: general type (i.e. negatively curved), Calabi-Yau (i.e. flat),
and Fano (i.e. positively curved, where the theory is connected to the
existence of KE metrics). Time permitting, we will use this motivation to
discuss moduli spaces of K3 surfaces (simply connected compact complex
surfaces with a no-where vanishing holomorphic 2-form).

(A joint seminar with the Geometry & Topology Seminar series.)

Typical comparison results in Riemannian geometry, such as for
volume or for spectrum of the Laplacian, require Ricci curvature lower
bounds. In dimension three, we can prove several sharp comparison estimates
assuming only a scalar curvature bound. The talk will present these results,
their applications, and describe how dimension three is used in the proofs.
Joint work with Jiaping Wang.

In this talk, I will present parts of a recent paper written
jointly with Mario Garcia-Fernandez and Jeff Streets ("NonKahler Calabi-Yau
Geometry and Pluriclosed Flow" arxiv:2106.13716). In particular, I intend to
discuss long-time existence and convergence of solutions to pluriclosed flow
on manifolds satisfying a flatness condition. As the pluriclosed flow does
not admit a scalar reduction in general, I will introduce the language of
holomorphic Courant algebroids and a result of J.M. Bismut that will allow
us to derive apriori estimates for an equivalent coupled
Hermitian-Yang-Mills-type flow.

The equations of flux compactifications of Type IIA superstrings were written down by Tomasiello and Tseng-Yau. To study these equations, we introduce a natural geometric flow on symplectic Calabi-Yau 6-manifolds. We prove the wellposedness of this flow and establish the basic estimates. We show that the Type IIA flow can be applied to find optimal almost complex structures on certain symplectic manifolds. It can also be used to prove a stability result about Kahler structures. This is based on joint work with Phong, Picard and Zhang.