报告人：王卫 教授
报告题目： On the Spectral Characterizations of Tournaments
报告时间：2022年1月21日（周五）上午09:00
报告地点：腾讯会议（会议ID：582-237-196）
主办单位：数学与统计学院、科学技术研究院
报告人简介：
王卫，西安交通大学教授、博士生导师。1991年于浙江大学应用数学专业获理学学士学位，分别于1994年及2002年于西安交通大学获理学硕士及博士学位。主要研究领域为代数图论与组合最优化。在图谱理论的研究中对图的广义谱刻画问题做出了一些原创性的工作，在组合优化领域中对一些NP-困难组合优化问题设计出了一些好的近似算法。目前在J. Combin. Theory, Ser B, European J. Combinatorics, 以及IEEE/ACM Transactions系列等刊物上发表研究论文80余篇。主持（完成）国家自然科学基金面上项目三项。
报告摘要：
Characterizing graphs by various spectra has long been a centraltopic in spectral graph theory. However, it is generally very hard to show agiven graph to be determined by its spectrum. In this talk, we shall give asimple criterion for a tournament to be determined by its adjacency spectrum.More precisely, let G be a tournament of order n with adjacency matrix A, andW(G)=[e,Ae,…,A^{n-1}e] its walk matrix, where e is the all-one vector. We showthat, for any self-converse tournament G, if det W(G) is square-free, then G isuniquely determined by its adjacency spectrum among all tournaments. The resultis somewhat unexpected, which was achieved by employing some recent tools forshowing graphs being determined by their generalized spectra. This is a jointwork with Wei Wang and Lihong Qiu.
邀请人：卢勇