Schedule 
Rooms 
Topics 
Tue 09/12 2:00 PM 
数理楼661 
Organizational meeting.

Tue 09/19 2:30 PM 
数理楼661 
Siyuan Ma (Albert Einstein Institute) "On Maxwell field and linearized gravity in Kerr spacetime"
Abstract: After the publication of Einstein's theory of General Relativity in 1915, many predictions have been confirmed in the latest one century, culminating at the recent observations of gravitational waves emitted during the merging of binary black holes by LIGO and VIRGO collaborations. Black holes are one of the fundamental predictions, and the one of most interests is the Kerr black hole spacetimes. The metric of a Kerr spacetime describes a rotating, stationary, axisymmetric, asymptotically flat solution to vacuum Einstein equations. One of the most important open problems in mathematical General Relativity is to address the fully nonlinear stability conjecture of Kerr solutions. In this talk, I will present recent results in obtaining energy estimates for both Maxwell field and linearized gravity on Kerr backgrounds, which will advance the field towards this conjecture. 
Tue 09/19 3:40 PM 
数理楼661 
Chao Liu (Monash University) "Cosmological Newtonian limits on large scales"
Abstract: In this talk, I will rigorously answer one basic question in cosmological simulation: on what space and time scales Newtonian cosmological simulations can be trusted to approximate relativistic cosmologies? We resolve this question under a small initial data condition. 
Tue 09/26 2:30 PM 
数理楼661 
Guofang Wang (Freiburg University) "Local Lagrangian embeddings and Hessian surfaces"
Abstract: We will talk about Local Lagrangian embeddings and Hessian surfaces. This is a joint work with Qing Han.

Tue 10/17 2:30 PM 
数理楼661 
Bo Yang (Xiamen University) "KahlerRicci flow on noncompact manifolds (after HuangTam and LeeTam)"
Abstract: This talk is purely expository. We explain recent works on KahlerRicci flow on complete noncompact Kahler manifolds with non collapsed volume and nonnegative bisectional curvature.

Tue 10/24 2:30 PM 
数理楼661 
Fei He (Xiamen University) "Existence of Ricci flow on noncompact manifolds"
Abstract: This will be a continuation of Bo Yang's talk from last week. We will discuss the shorttime existence of Ricci flow on noncompact manifolds with a focus on the recent work of Lee and Tam.

Fri 11/03 2:30 PM 
实验楼105 
Xi Zhang (University of Science and Technology of China) "Canonical metrics and The HermitianYangMills flow on reflexive sheaves"
Abstract: In this talk, we will introduce our recent work
on the existence of canonical metrics, Bogomolov type inequalities and the limiting behavior of the HermitianYangMills flow on reflexive sheaves. These work are joint with JiaYu Li, YanCi Nie and ChuanJing Zhang.

Fri 11/10 2:30 PM 
实验楼105 
Bin Zhou (Peking University) "Kenergy on polarized compactifications of Lie groups"
Abstract: In this paper, we study Mabuchi’s Kenergy on a compactification M of a reductive Lie group G, which is a complexification of its maximal compact subgroup K. We give a criterion for the properness of Kenergy on the space of K × Kinvariant Kahler potentials. In particular, it turns to give an alternative proof of Delcroix’s theorem for the existence of KahlerEinstein metrics in case of Fano manifolds M . We also study the existence of minimizers of Kenergy for general Kahler classes of M.

Fri 11/10 3:40 PM 
实验楼105 
Weiming Shen (BICMR, Peking University) "On The Negativity of Ricci Curvatures of Complete Conformal Metrics"
Abstract: A version of the singular Yamabe problem in bounded domains yields complete conformal metrics with negative constant scalar curvatures. In this talk, I will disscuss whether these metrics have negative Ricci curvatures. We will provide a general construction of domains in compact manifolds and demonstrate that the negativity of Ricci curvatures does not hold if the boundary is close to certain sets of low dimension. The expansion of the Green's function and the positive mass theorem play essential roles in certain cases. On the other hand, we prove that these metrics indeed have negative Ricci curvatures in bounded convex domains in the Euclidean space.

Fri 11/17 3:30 PM 
实验楼105 
Xiao Zhang (AMSS, Beijing) " The positive energy theorem for asymptotically hyperbolic manifolds"
Abstract: In general relativity, asymptotically hyperbolic manifolds serve as the initial data sets in two cases:
(i) asymptotically null infinity for asymptotically flat spacetimes where the cosmological constant is zero;
(ii) asymptotically spatial infinity for asymptotically AdS spacetimes where the cosmological constant is negative.
The difference is that, in case (i), the second fundamental forms are asymptotic to hyperbolic metrics while in case (ii), the second fundamental forms are asymptotic to zero. We will discuss the positive energy theorem in the two cases. The talk is based on the early work of the speaker as well as the joint work with Wang Yuahua and Xie Naqing.

Fri 11/24 2:30 PM 
实验楼105 
Zhizhang Wang (Fudan University) "The curvature estimates for convex solutions of some fully nonlinear Hessian type equations"
Abstract: The curvature estimates of quotient curvature equation do not always exist even for convex setting. Thus it is natural question to find other type of elliptic equations possessing curvature estimates. In this paper,
we discuss the existence of curvature estimate for fully nonlinear elliptic equations defined by symmetric polynomials, mainly, the linear combination of elementary symmetric polynomials. This is a joint work with Chunhe Li and Changyu Ren.

Fri 11/24 3:40 PM 
实验楼105 
Naqing Xie (Fudan University) "Toroidal marginally outer trapped surfaces in the closed FriedmannLemaitreRobertsonWalker universe"
Abstract: We explicitly construct toroidal MOTS in the closed FLRW universe. This construction is used to assess the quality of certain isoperimetric inequalities recently proved in axial symmetry. We also show that these constructed toroidal MOTS are unstable. This talk is based on a joint work with Patryk Mach.

Fri 12/01 2:30 PM 
实验楼105 
Frederick TszHo Fong (Hong Kong University of Science and Technology) "Rigidity of SelfExpanders of Inverse Curvature Flows"
Abstract: In this talk, the speaker will investigate a large class of curvature flows by degree 1 homogeneous functions of principal curvatures in Euclidean spaces. This class curvature flows include the wellknown inverse mean curvature flow and many others in the current literature. Selfexpanding solutions to these curvature flows are solutions that expanding homothetically without changing their shapes. We will talk about uniqueness, rigidity, and constructions of both compact and noncompact selfexpanding solutions to these flows. Part of these are joint work with G. Drugan, H. Lee; P. McGrath; and A. Chow, K. Chow.

Fri 12/08 3:30 PM 
实验楼105 
Hui Ma (Tsinghua University) "Uniqueness of closed selfsimilar solutions to $\sigma_k^{\alpha}$curvature flow"
Abstract: In this talk we will show the uniqueness of closed selfsimilar solutions to $\sigma_k^{\alpha}$curvature flow. It is based on the joint work with Shanze Gao and Haizhong Li.

Fri 12/22 3:00 PM 
实验楼105 
Daniel Zhuangdan Guan (UC Riverside) "Recent progress on compact KaehlerEinstein manifolds with cohomogeneity one metrics"
Abstract: Although there are many known K\"ahlerEinstein manifolds, there is so far no very practical method to check a given compact Fano manifold to be K\"ahlerEinstein or not.This is also true for the K\"ahler metrics with constant scalar curvatures or Calabi extremal metrics. The situation for a cohomogeneity one metrics was completely resolved.For the type III case, it was solved in my dissertation in 1992. For the remain type I and II case, the existence is equivalent to the negativity of a topological integral.The type I case was published in 2011. Therefore, the problem is reduced to check the negativity for classes of Fano manifolds. Recently, we use computer to get some insight into a class of type I Fano manifolds. This work is a joint work with a group of students. .

Wed 12/27 3:00 PM 
行政楼313 
Daniel Zhuangdan Guan (UC Riverside) "Recent Progress in the classification of complex homogeneous spaces"
Abstract: A manifold M is a homogeneous space if M=G/H with G a finite dimensional group and H a closed subgroup. M is a complex homogeneous space if J is the given complex structure on M such that J is invariant under the action of G. Homogeneous space is a classical area of differential geometry.The most famous work was the classification of real (and complex) semisimple Lie groups and the symmetric spaces. The K\"ahler homogeneous space was classified by Dorfmeister and Nakajima in 1988. The pseudok\"ahler homogeneous space with reductive G was classified by Dorfmeister and Guan in 1989. In the general compact complex homogeneous case, the classification reduced to the parallelizable case, i.e., in which H is discrete. In the late 1990's we proved that if G/H is a compact complex parallelizable manifold,then the semisimple part of G is locally a product of complex simple Lie group of type A.A classification of the compact complex homogeneous space with an invariant volume was also finally classified.A complete classification of the compact complex space with a pseudok\"ahler structure (nonnecessary invariant) was given in 2007. Recently, compact complex homogeneous space with an invariant locally conformal K\"ahler structure was classified and similarly for the cohomogeneity one case.

Fri 12/29 2:30 PM 
实验楼105 
Yunhui Wu (Tsinghua University) "The WeilPetersson geometry of the moduli of curves for large genus"
Abstract: We study the systole function along WeilPetersson geodesics. We show that the square root of the systole function is uniform Lipschitz on the Teichmuller space endowed with the WeilPetersson metric. As an application, we study the growth of the WeilPetersson inradius of the moduli space of Riemann surfaces of genus $g$ with $n$ punctures as a function of $g$ and $n$. We show that the WeilPetersson inradius is comparable to $\sqrt{\ln{g}}$ with respect to $g$, and is comparable to $1$ with respect to $n$.

Fri 12/29 3:30 PM 
实验楼105 
Qing Han (University of Notre Dame) "Nonexistence of PoincareEinstein Fillings on Spin Manifolds"
Abstract: In this talk, we discuss whether a conformal class on the boundary M of a given compact manifold X can be the conformal infinity of a PoincareEinstein metric in X. We construct an invariant of conformal classes on the boundary M of a compact spin manifold X of dimension 4k with the help of the Dirac operator. We prove that a conformal class cannot be the conformal infinity of a PoincareEinstein metric if this invariant is not zero. Furthermore, we will prove this invariant can attain values of infinitely many integers if one invariant is not zero on the above given spin manifold. This talk is based on a joint work with Gursky and Stolz.

Tue 01/09 2:30 PM 
数理楼661 
Guohuan Qiu (McGill University) "Interior Hessian estimates for sigma2 equations in dimension three"
Abstract: The interior regularity for solutions of the sigma_2 Hessian equation is a longstanding problem.Heinz first derived this interior estimate in dimension two. For higher dimensional MongeAmpere equations, Pogorelov constructed his famous counterexamples even for f constant and convex solutions. CaffarelliNirenbergSpruck studied more general fully nonlinear equations such as \sigma_{k} equations in their seminal work. And Urbas also constructed counterexamples with k greater than 3. The only unknown case is k=2. A major breakthrough was made by WarrenYuan, they obtained a prior interior Hessian estimate for the equation \sigma_2=1 in dimension three.In this talk, I will present my recent work on how to deal this problem for a more general case in dimension three.

Fri 01/12 3:30 PM 
实验楼105 
Xingwang Xu (Nanjing University) "Q and R"
Abstract: In this talk, I should focus on the conformal invariant equations of higher order. We interpolate them in terms of conformal geometry. Natural geometric information provides the maximum principle for such equations. This is a joint work with Mr. Weixi Wang.

Fri 01/12 4:30 PM 
实验楼105 
Robert Kusner (University of Massachusetts at Amherst) "Coplanar CMC surfaces, complex projective structures, and polynomial quadratic differentials"
Abstract: Complete embedded constant mean curvature (CMC) surfaces of fixed, finite topology form a finitedimensional moduli space. This moduli space is a realanalytic variety parametrized by the asymptotic data of the surfaces, and possibly by some squareintegrable Jacobi fields. For coplanar CMC surfaces of genus 0 with k ends, such Jacobi fields must vanish, and this moduli space can be explicitly described: it is diffeomorphic to the space of kpoint spherical metrics; these can be described, in turn, by holomorphic immersions from the plane to the 2sphere whose Schwarzian is a polynomial with degree depending on k. The CMC surfaces corresponding to the polynomials 0 and 1 are, respectively, the round sphere and the 1parameter family of unduloids, while those which correspond to the polynomial z are the 3parameter family of triunduloids. Byviewing the Schwarzian as a quadratic differential and its real foliations, a compelling picture of this correspondence emerges. (If time permits, a new construction of coplanar CMC surfaces with genus 1, all of whose ends are cylindrical, will also be described.).

Thu 01/18 2:30 PM 
实验楼108 
Miaomiao Zhu (Shanghai Jiaotong University) "Existence of solutions of a boundary value problem for Diracharmonic maps"
Abstract: In this talk, we shall present some recent progresses on the heat flow approach to the existence of solutions of a boundary value problem for Diracharmonic maps. These are joint works with Jurgen Jost and Lei Liu.
