澳门新葡萄京997755

1月18日 王周宁馨博士学术报告(数学与统计学院)

编辑:时间:2019-01-15浏览:201设置

报 告 人:王周宁馨 博士

报告题目:Homomorphisms of signed $K_4$-subdivisions

报告时间:2019年1月18日(周五)上午9:00-10:30

报告地点:静远楼1508报告厅

主办单位:数学与统计学院、科学技术研究院

报告摘要:

  A homomorphism of a signed graph $(G, \Sigma)$ to $(H, \Pi)$ is a mapping from the vertices and edges of $G$, respectively, to the vertices and edges of $H$ such that adjacencies, incidences, and signs of closed walks are preserved. Given a class $\mathcal{C}$ of signed graphs, we say signed graph $(H, \Pi)$ homomorphically bounds the class $\mathcal{C}$  if every signed graph in $\mathcal{C}$ admits a homomorphism to $(H, \Pi)$.The core of a signed graph $(G, \Sigma)$ is the minimal subgraph $(G, \Sigma’)$ of this signed graph, such that there exists a homomorphism of $(G, \Sigma)$ to $(G, \Sigma’)$. Motivated by studies on bounds of sparse signed graphs, such as Jaeger-Zhang Conjecture or its bipartite analogue introduced by Charpentier, Naserasr and Sopena, we characterize those signed $K_4$-subdivisions which are cores. We also characterize those signed graphs which would homomorphically bound the class of signed $K_4$-minor free graphs.

  This is joint work with Reza Naserasr.


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