Speaker: Prof. Todd Hyster (Princeton University)Inviter: Prof. JI Pengfei (Zhejiang University)Venue: C225, Building 5, Haina Court, Zijingang Campus

Venue: Room 210, Building 2, Haina Court, Zijingang CampusSpeaker: Prof. WANG Buotuo (University of Wisconsin–Madison)Abstract: Many important posets (partially ordered sets) in combinatorics have algebriac interpretations. We will go over three families of examples: toric varieties, Schubert varieties and matroid Schubert varieties. We will discuss how to translate some of the combinatorical invariants into the geometric ones, and the application of intersection cohomology groups in solving combinatorical problems.

Speaker: Dr. LIU Qicheng (Peking University)Venue: Room 101, Building 2, Haina Court, Zijingang CampusAbstract: In this talk, I will introduce the reconstructed discontinuous approximation (RDA) method for solving second-order elliptic problem with an efficient preconditioner. The RDA method uses a reconstructed high-order approximation space which is constructed by solving a local constrained least squares problem. One attractive feature for the reconstructed space is that it has only one degree of freedom per element. This space can be directly used with the symmetric/nonsymmetric interior penalty discontinuous Galerkin method. Further, an efficient preconditioner can be constructed from the piecewise constant space. The upper bound of the condition number to the preconditioned symmetric/nonsymmetric system is shown to be independent of the mesh size. Numerical experiments are provided to demonstrate the validity of the theory and the efficiency of the proposed method.Contact person: Prof. ZHANG Qinghai （0015089@zju.edu.cn）

Speaker: Dohan Kim (Seoul National University, Korea)Venue: Room 105, Building 2, Haina Court, Zijingang CampusAbstract: 1) From Almost Nothing to Fields Medal;2) Academic Exchange between China and Korea in Mathematics.Contact person: Junde Wu (wjd@zju.edu.cn)Curriculum vitae of speaker:1) PersonalBirth Date: May 15, 1950.2) EducationB.S. in Electronics Engineering, Seoul National University, 1972M.S. in Mathematics, Seoul National University, 1974Ph. D. in Mathematics, Rutgers University (Thesis Adviser, F. Treves), 19813) Experience in Seoul National UniversityProfessor, 1992~Chairman, Department of Mathematics, 2003~ 2005Deputy Director & Director, BK21 Mathematical Science Division SNU, 1999~20064) Professional Organization Korean Mathematical SocietyVice President 1997~ 2006President, 2007~ 20105) National Academy of Science, Republic of KoreaMember, since 2016Chair, Division I of Science, 2018~ 20196) Korean Academy of Science and TechnologyMember, since 2006Chair, Division of Science, 2016~2019Chair, Prize Committee, since 20197) International Congress of Mathematicians, Seoul 20142011~2014 Chair, Advisory Committee, Organizing Committee for 2014 ICM at Seoul2013 Chair, Organizing Committee, AMC 2013 (Asian Mathematical Conference) at Busan8) Area of SpecializationDistributions and HyperfunctionsFourier AnalysisLinear Partial Differential EquationsOrdinary Differential Equations

Venue: Room 210, Building 2, Haina Court, Zijingang Campus

Speaker: Prof. JI Rurong (Duke University)Venue: Room 205, Complex Building, School of Medicine, Zijingang CampusHost: Prof. GAO Zhihua (Zhejiang University)

Speaker: Prof. TU Yundong (Peking University)Venue: Room 206, Building 2, Haina Court, Zijingang CampusAbstract: This paper explores the group structure in large dimensional approximate factor models, which portrays homogeneous effects of the common factors on the individuals that fall into the same group. With the initial principle component estimates, we identify the unknown group structure by a combination of the agglomerative hierarchical clustering algorithm and an information criterion. The loadings and factors are then re-estimated conditional on the identified groups. Under some regularity conditions, we establish the consistency of the membership estimator as well as that of the group number estimator obtained from the information criterion. The new estimators under the group structure are shown to achieve efficiency gain compared to those obtained without this information. Numerical simulations and empirical applications demonstrate the nice finite sample performance of our proposed approach when group structure presents.Contact person: Prof. ZHANG Rongmao (rmzhang@zju.edu.cn)

Speaker: Dr. LI Mingxiang (Nanjing University)Venue: Room 105, Building 2, Haina Court, Zijingang CampusAbstract: In this talk, we will introduce some rigidity theorems on complete and conformally flat manifolds with help of Q-curvature. We introduce a new volume entropy to give a sufficient and necessary condition for the ”normal” metric. Meanwhile, with help of geometric measure theory, we give a distance comparison identity on such manifolds which generalize the result of Li-Tam(1991, JDG) to higher dimensions. Finally, we want to talk about higher order Bol’s inequality which is a joint work with Professor Juncheng Wei.Contact person: Prof. JIANG Wenshuai (wsjiang@zju.edu.cn)

Speaker: Prof. Jianfeng Lin (Tsinghua University)Venue: Lecture Hall, East Building 7, Zijingang Campus