The theory of Gromov-Witten invariants is a curve counting theory defined by integration on the moduli of stable maps. Varying the stability condition gives alternative compactifications of the moduli space and defines similar invariants. One example is epsilon-stable quasimaps, defined for a large class of GIT quotients. When epsilon tends to infinity, one recovers Gromov-Witten invariants. When epsilon tends to zero, the invariants are closely related to the B-model in physics. The space of epsilon's has a wall-and-chamber structure. In this talk, I will explain how wall-crossing helps to compute the Gromov-Witten invariants and sketch a proof of the wall-crossing formula.

Combustion or ignition equation is a special reaction diffusion equation which is used to describe the propagation of flames. In this talk we consider the Cauchy problem and the Stefan free boundary problem for such equations. We will specify the asymptotic behavior for the solutions, in particular, the spreading phenomena and its feature in these problems.

题目：Variance Reduced Median-of-Means Estimator for Byzantine-Robust Distributed Inference报告人：刘卫东 教授（上海交通大学）地点：腾讯会议室时间：2021年10月13日（周三） 晚上19:30摘要：This talk develops an efficient distributed inference algorithm,  which is robust against a moderate fraction of Byzantine nodes, namely arbitrary and possibly adversarial machines in a distributed learning syst...

在这个数据科学越来越受到重视，数据越来越受到重视的今天，数据的科学治理与合规使用，也变得越来越重要。本次报告，围绕以下几个方面：第一、目前我们看到的数据合规案例和问题有哪些。第二、目前我国同数据合规使用相关的法律条文有哪些。第三、在过去的这些年里，同数据相关的司法诉讼经典案例，做有挑选的探讨。最后，对我国数据合规使用有指导性的基本原则做了总结。

I will present some recent work on the heat equation and the biharmonic heat equation on complete Riemannian manifolds, including: uniqueness criteria for the heat equation and the biharmonic heat equation, estimates of the biharmonic heat kernel, and a uniform L-infinite estimate for solutions of the biharmonic heat equation with bounded initial data.

We develop a dynamic tractable model where an investor derives realization utility as in Barberis and Xiong (2012) and Ingersoll and Jin (2013), but importantly can dynamically rebalance her portfolio between a risky asset and a risk-free asset. We show that the option of investing in the risk-free asset is quite valuable, even though the investor only derives utility from realized gains and losses of trading the risky asset. We also find that the investor may realize losses after a slight rally following a crash. This work is jointly with Cong Qin and Neng Wang

本报告主要讨论了空间周期介质中，双稳型方程周期行波解的波速对方向的依赖性。对于一维空间中的Fisher-KPP方程，由最小波速的变分表达式可知左右两个相反方向上的最小波速一定是相同的。但对于双稳方程，我们发现两个相反方向上的（唯一）波速可以相差很大。这个结论也被推广到高维情形和多稳定情形。在高维空间中，我们证明了在任意有限多个方向上，行波解波速可以相差很大，并由此指出：渐近传播速度可以严格小于行波解波速。在多稳态情形，我们发现左右两个方向上递归型行波解（propagating terrace）的形状、中间平衡态的个数、传播速度等都可以不同。报告是基于与Thomas Giletti 合作的工作。

We introduce a class of functional analogs of the symmetric difference metric on the space of coercive convex functions on R^n with full-dimensional domain. We show that convergence with respect to these metrics is equivalent to epi-convergence. Furthermore, we give a full classification of all isometries with respect to some of the new metrics. Moreover, we introduce two new functional analogs of the Hausdorff metric on the spaces of coercive convex functions and super-coercive convex functions, respectively, and prove equivalence to epiconvergence.