Title: Flows of signed graphs)
Speaker: Prof. Rong Luo (West Virginia University, USA)
Time: 2019-11-18 (Monday) 15:00
Inviter: Prof. Liying Kang
It was observed by Tutte that the problem of the face-coloring (map coloring) of a graph embedded on an orientable surface can be formulated in terms of integer flows of the graph. It was further extended by Bouchet (JCTB 1983) for graphs on non-orientable surfaces. For graphs embedded on non-orientable surfaces, the dual version of vertex-coloring is the flow problem for signed graphs. An edge is negative if it passes through an odd number of crosscaps. Bouchet (JCTB 1983) conjectured that every flow admissible signed graph admits a nowhere-zero 6-flow. In this talk, I will report the progresses we make toward Bouchet's 6-flowo conjecture.