Enumerative problems for minimal surfaces of prescribed genus. It was conjectured by B. White (1989) that every Riemannian 3-sphere contains at least 5 minimal tori. Joint with Y. Li, we confirmed this for metrics of positive Ricci curvature using min-max theory [link]. Recently, I also showed that every Ricci-positive 3-sphere contains a genus g minimal surface for every g [link]. See this page for an introduction.
Gluing construction for minimal surfaces. Joint with D. Stern, we proved that every Riemannian 3-manifold with generic metric contains infinitely minimal surfaces with bounded area [link]. Our proof uses the doubling construction developed by Kapouleas-McGarth. In particular, this gives a new solution to Yau's conjecture (1982) in the generic metric setting.
Singularities in geometric flow. Together with A. Sun, we found some topological criteria that ensures the appearance of some genus one singularity in mean curvature flow [link]. As an application, we constructed a genus one self-shrinker with entropy less than the shrinking doughnut.