讲座题目：Density and spanning trees of A-connected graphs

主讲人：Prof. Rong Luo（罗荣教授）

主持人：吕长虹教授

开始时间：2016-3-20  10:00-11:00

讲座地址：闵行数学楼126室

报告人简介：

罗荣教授是美国West Virginia University数学系教授，国际知名图论研究专家。他主要研究兴趣在图的整数流、图的染色、图的连通性等图论重要研究领域，发表了40多篇学术论文，多发表在J. of Combin. Theory (B)、Euorp. J. Combin、SIAM J. Discret. Math等组合图论领域顶尖期刊上。

报告内容简介：

Let A be an Abelian group. It is known that an A-connected graph cannot be very sparse. We study the extremal problem: find the maximum integer k, denoted ex(n, A), such that every graph with at most k edges is not A-connected. We determine the exact values for all finite cyclic groups.  As a corollary, we present a characterization of all Z_k-connected graphic sequences. It is also known that there are Z_5-connected graph that are not Z_6-connected. We prove that every Z_3-connected graph contains two edge-disjoint spanning trees, which implies that every Z_3-connected graph is also A-connected for any A with order at least 4.

数学系

核心数学与实践重点实验室