时间：2024.5.17（周五）上午10:00-11.30

地点：数学楼112会议室

题目：An isoperimetric problem on graphs: q-Kneser graph and derangement graph

摘要：In the late 1960's, Kruskal and Katona solved independently an isoperimetric problem in the high-dimensional simplex. A general Kruskal-Katona-type problem on graphs is to describe subsets of the vertex set of a graph with minimum number of neighborhoods with respect to their own sizes. We report a Kruskal-Katona-type theorem for the derangement graph of the symmetric group on a finite set. Our result not only implies the Erdos-Ko-Rado theorem for intersecting families in the symmetric group but also leads to a short proof of the Cameron-Ku conjecture on nontrivial intersecting families in the symmetric group.

报告人简介：王军，上海师范大学数理学院教授（二级）， 曾任中国数学会组合与图论专业委员会副主任（2006-2018）以及上海师范大学数理学院学术委员会主任等职。主要的研究领域是组合数学，近年来工作重点在有限集上的组合，解决了其中一些引人注目的问题和猜想。曾多次参加或主持国家级和省部级自然科学基金项目，曾被选为辽宁省百千万人才工程百人层次人选并享受政府特殊津贴。