In this talk, using the local Ricci flow, we prove the short-time
existence of the Ricci flow on noncompact manifolds, whose Ricci curvature
has global lower bound and sectional curvature has only local average integral
bound. The short-time existence of the Ricci flow on noncompact manifolds
was studied by Wan-Xiong Shi in 1990s, who required a point-wise bound of
curvature tensors. As a corollary of our main theorem, we get the short-time existence part of Shis theorem in this more general context.
In this talk by using the idea in the proof of Perelman's pseudo locality theorem we will derive a local curvature bound in Ricci flow assuming only local sectional curvature bound and local volume lower bound for the initial metric.
This result is closely related to Theorem 10.3 in Perelman's entropy paper.
This is a joint work with Lu Xu. We establish a geometric lower bound for the principal curvature of the level surfaces of solutions to $F(D^2u, Du, u, x)=0$ in convex ring domains, under a refined structural condition introduced by Bianchini-Longinetti-Salani.
We show the convergence of Kahler Ricci flow on every 2-dimensional orbifold if the underlying orbifold has big $\alpha_{\nu, 1}$
or $\alpha_{\nu, 2}$ (Tian's invariants). We then find some new Kahler Einstein metrics on orbifolds by calculating Tian's invariants.
We construct smooth forward Ricci flow evolutions of singular initial metrics resulting from rotationally symmetric neckpinches, without performing an intervening surgery. In the restrictive context of rotational symmetry, the construction gives evidence in favor of Perelman's hope for a "canonically defined Ricci flow through singularities". This is joint work with Sigurd Angenent and Cristina Caputo.