报告题目：On the second out-neighborhood and the girth of digraphs
报告人：李瑞娟
报告时间：2023年6月18日09:00-12:00
报告地点：科技园一号楼南815
邀请单位：福州大学数学与统计学院，离散数学及其应用省部共建教育部重点实验室
报告摘要：
Seymour's Second Neighborhood Conjecture asserts that for an oriented graph 
, there exists a vertex 
in such that 
. Caccetta-Häggkvist conjecture asserts that for an 
-vertex digraph with minimum out-degree 
, the girth is at most 
. As we know SSNC is the special case of C-H conjecture when both in- and out-degrees are at least 
. In this talk, we discuss the second out-neighborhood and the girth in a local tournament, bipartite tournament, quasi-tournament, oriented graph of order with minimum degree at least 
and so on. We also introduce the current research status and progress, the approaches and technique as well as open problems related to the topics.
报告人简介：
李瑞娟，山西大学数学科学学院教授，博士生导师，毕业于德国亚琛工业大学。山西省高校优秀青年学术带头人，山西省高校131领军人才，山西省 “三晋英才”支持计划青年优秀人才。主要从事图论领域中的结构图论、有向图等方向的理论研究，多次主持国家自然科学基金和省部级的项目。在Journal of Graph Theory, Discrete Mathematics, Discrete Applied Mathematics, Graphs and Combinatorics等学术期刊上发表论文40余篇，撰写专著2部。
