*主持人：叶东 教授

*讲座内容简介：
Motivated by studies of axially symmetric stationary solutions of the Einstein vacuum equations in general relativity, we study singular harmonic maps from domains of the 3-dimensional Euclidean space to the hyperbolic plane, with bounded hyperbolic distance to extreme Kerr harmonic maps. We prove that every such harmonic map has a unique tangent map at the black hole horizon. As an application, we establish an explicit and optimal lower bound for the ADM mass in terms of the total angular momentum, in asymptotically flat, axially symmetric, and maximal initial data sets for the Einstein equations with multiple black holes.

*主讲人简介：
韩青，美国圣母大学数学系教授。美国纽约大学库朗数学研究所博士，美国芝加哥大学博士后，曾在德国莱比锡马普所和美国纽约大学库朗数学研究所进行科研，获美国Sloan Research Fellowship。 韩青教授长期致力于非线性偏微分方程和几何分析的研究工作，在等距嵌入、Monge-Ampere方程、调和函数的零点集和奇异集、退化方程等方面做出了一系列原创性的重要研究成果。