Geometric Flows, Geometric Inequalities, and Rigidity of Embeddings

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This project is focused on questions in differential geometry. The aim of differential geometry is to study higher-dimensional shapes and their curvature. In particular, these concepts provide a mathematical framework for general relativity. Geometric flows are a key tool in differential geometry. The idea here is to take a geometric object and evolve it by a differential equation in order to smooth it out. These differential equations share common features with heat diffusion. However, the differential equations that arise in geometry tend to be nonlinear, which presents challenges in their analysis. A main focus is to understand the behavior of these equations when the solution becomes singular, that is, when the curvature becomes very large. An important problem is to classify the singularity models; these are the limiting shapes that occur at a singularity. Another major goal in geometry is to understand geometric inequalities. A basic example is the isoperimetric inequality (which states that balls have smallest surface area among all shapes that enclose a given amount of volume), but many other types of inequalities are of importance in differential geometry. The project also includes training of PhD students and mentoring of post-doctoral researchers.The primary examples of geometric flows are the Ricci flow and the mean curvature flow. The mean curvature flow is the most natural evolution equation for a surface embedded in Euclidean space, while the Ricci flow is the most natural evolution equation for a Riemannian metric. The Ricci flow has become an indispensable tool in differential geometry. Among other things, the Ricci flow lies at the heart of Perelman's proof of the Poincare conjecture. The PI will study what types of singularities can form under these evolution equations. For example, it would be very interesting to understand whether a plane of multiplicity 2 can arise as a singularity model under the mean curvature flow. In another direction, the PI will study problems related to geometric inequalities. In particular, it would be very interesting to understand isoperimetric inequalities in negatively curved manifolds. Moreover, many geometric inequalities come with an associated rigidity statement which characterizes the case of equality. The PI will study the near-equality case in such inequalities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.