报告名称：Flows of signed graphs

主办单位：英国威廉希尔体育公司

报告专家：罗荣

专家所在单位：WestVirginia University

报告时间：2021年5月13日9：00

报告地点：腾讯会议（会议ID：826 899 282）

专家简介：罗荣，美国西弗吉尼亚大学（WestVirginia University，USA）数学系教授。主要研究图的染色理论和流的理论，是国际知名的染色问题专家。发表近60余篇论文，多数是发表在图论顶尖杂志如Journal ofCominatorial Theory Ser. B, Journal of Graph Theory, SIAM Journal on DiscreteMath, and European J. of Combinatorics. 在Vizing上世纪60年代末提出的四个关于边染色的猜想取得了一系列突破性进展。解决了几个著名公开问题如Erdos、Gould、Jacobson以及Lehel提出的一个关于可图序列猜想，Borodin提出的边面染色的问题，Archdeacon关于三流可图序列的问题。

报告摘要：Nowhere-zero flows of unsigned graphs were introduced by Tutte in 1954 as a dual problem to vertex-coloring of (unsigned) planar graphs. The definition of nowhere-zero flows on signed graphs naturally comes from the study of embeddings of graphs in non-orientable surfaces, where nowhere-zero flows emerge as the dual notion to local tensions. Nowhere-zero flows in signed graphs were introduced by Edmonds and Johnson in 1970 for expressing algorithms on matchings, but systematically studied first by Bouchet in 1983. Bouchet also stated a conjecture which occupies a central place in the area of signed graphs: Every flow-admissible signed graph admits a nowhere-zero 6-flow. There is significant difference on the flows of signed graphs and unsigned graphs. In this talk I will talk about the progress on the development of the flow theory of signed graphs.

邀请人：刘慧清

（审稿：郑大彬）