校 级 学 术 报 告

题目： The Sum of Unitary Similarity Orbits
Containing Only Special Operators
报告人：Chi-Kwong Li 教授
College of William and Mary, USA
时间：5月21日 （周三）下午3：00
地点：闵行校区4号教学楼 214
摘要：Let BH be the algebra of bounded linear operators acting on a Hilbert space H (over the complex or real field). Characterization is given to A_1, …, A_k in BH such that for any unitary operators U_1, …, U_k, sum_{j=1}^k U_j^*A_jU_j is always in a special class S of operators such as normal operators,self-adjoint operators, unitary operators. As corollaries, characterizations are given to A in BH such that the (real) linear or nonnegative combinations of operators in its unitary orbits U(A) = {U^*AU: U unitary} always lie in S.

报告人简介：
Chi-Kwong Li 教授是美国威廉和玛丽学院的Ferguson教授、国际线性代数学会副主席、 Linear and Multilinear Algebra 和 Operators and Matrices 两本杂志的主编、 Linear Algebra and its Applications 和 J. of Inequalities in Pure and Applied Mathematics 两本杂志的编委、矩阵分析和算子理论领域领头的专家之一。