Li-Yau estimates under new curvature conditions and their applications

Speaker: 

Meng Zhu

Institution: 

UC Riverside

Time: 

Tuesday, October 6, 2015 - 4:00pm

Location: 

RH 306

We will introduce two new Li-Yau estimates for the heat equation
on manifolds under some new curvature conditions. The first one is obtained
for n-dimensional manifolds with fixed Riemannian metric under the
condition that the Ricci curvature being L^p bounded for some p>n/2. The
second one is proved for manifolds evolving under the Ricci flow with
uniformly bounded scalar curvature. Moreover, we will also apply the first
Li-Yau estimate to generalize Colding-Naber's results on parabolic
approximations of local Busemann functions to weaker curvature condition
setting. This is a recent joint work with Richard Bamler and Qi S. Zhang.

Geometry of shrinking Ricci solitons

Speaker: 

Jiaping Wang

Institution: 

University of Minnesota

Time: 

Tuesday, November 3, 2015 - 4:00pm

Location: 

RH 306

Ricci solitons, as self-similar solutions to the Ricci flows, are important for understanding both the dynamic and singularity formation of the Ricci flows. The talk will primarily focus on the four dimensional shrinking Ricci solitons. We will explain some of the recent progress, made jointly with Ovidiu Munteanu, toward the structure at infinity of such solitons.

On pseudo-holomorphic curves in contact manifolds

Speaker: 

Rui Wang

Institution: 

UC Irvine

Time: 

Tuesday, September 29, 2015 - 4:00pm

Location: 

RH 306

In this talk, I will begin with introducing the method of
pseudo-holomorphic curves (which are defined by Cauchy-Riemnn type elliptic
systems) in the study of symplectic and contact topology. Then I will focus
on discussing the one studied by Yong-Geun Oh and myself recently, including
its potential, drawbacks and possible improvements towards the goal of a
better understanding in contact topology. (The similar elliptic system named
the generalized pseudo-holomorphic curves in symplectizations was introduced
by Hofer and studied by Abbas-Cieliebak-Hofer, Abbas in the proposal of
proving the Weinstein conjecture for dimension three.)

Classification of gravitational instantons

Speaker: 

Gao Chen

Institution: 

SUNY Stony Brook

Time: 

Tuesday, October 20, 2015 - 4:00pm

Host: 

Location: 

RH 306

A gravitational instanton is a noncompact complete hyperkahler manifold of real dimension 4 with faster than quadratic curvature decay. In this talk, I will discuss the recent work towards the classification of gravitational instantons. This is a joint work with X. X. Chen.

Minimal surfaces with bounded index

Speaker: 

Davi Maximo

Institution: 

Stanford University

Time: 

Tuesday, October 27, 2015 - 4:00pm

Host: 

Location: 

RH 306

We prove a structural theorem that provides a precise local picture of how a sequence of closed embedded minimal surfaces with bounded index on a given three-manifold might degenerate. We then discuss several applications, including some compactness results. Time permitting, we discuss how our strategy can be extended to ambient dimensions 4,5,6 and 7. (This is joint work with O. Chodosh and D. Ketover) 

Mathematical theory of gauged linear sigma model

Speaker: 

Guangbo Xu

Institution: 

UC Irvine

Time: 

Tuesday, May 19, 2015 - 4:00pm

Location: 

RH 306

In this talk I will review some mathematical theories of
A-models, including Gromov-Witten theory, FJRW theory and Gauged
Gromov-Witten theory. Then I will describe the project with Tian on the
construction of Gauged Linear Sigma Model which was introduced by Witten
in 1993.

Alexandrov's isodiametric conjecture and the cut locus of a surface

Speaker: 

David Krejcirik

Institution: 

Nuclear Physics Institute, Academy of Sciences, Czech Republic

Time: 

Tuesday, June 2, 2015 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

We prove that Alexandrov's conjecture relating the area and diameter of a convex surface holds for the surface of a general ellipsoid. This is a direct consequence of a more general result which estimates the deviation from the optimal conjectured bound in terms of the length of  the cut locus of a point on the surface. We also prove that the natural extension of the conjecture to general dimension holds among closed convex spherically symmetric Riemannian manifolds. Our results are based on a new symmetrisation procedure which we believe to be interesting in its own right.

This is joint work with Pedro Freitas accepted for publication in the Tohoku Mathematical Journal, preprint on http://arxiv.org/abs/1406.0811.

Witten deformations, scattering and mirror symmetry

Speaker: 

Conan Leung

Institution: 

Chinese University of Hong Kong

Time: 

Thursday, April 9, 2015 - 4:00pm

Location: 

Natural Sciences II 1201

In this talk, I will explain Morse category as a
Witten deformation of algebra structures on the space
of differential forms. Applications to symplectic geometry and
mirror symmetry will also be described. These are joint works with
K.L. Chan, K.W. Chan and Z.M. Ma.

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