报告题目：Kempe equivalence of $3$-edge-colorings in cubic graphs on the projective plane报告人：Kenta Ozeki (Yokohama National University, Japan) 

报告时间：5月3日周四 下午4:30-5:30
地点：5教 5307
摘要：
Let G be a cubic graph having a 3-edge-coloring c.For a 2-edge-colored cycle D, a Kempe switch (at D) is an operation to obtain another 3-edge-coloring by switching the colors of E(D). Two 3-edge-colorings in G are Kempe equivalent if one is obtained from the other by a sequence of Kempe switches. We partially answer this question, showing that a bipartite cubic graph G on the projective-plane admits only one Kempe equivalent class if and only if the dual G^* is not vertex-4-colorable. Mohar asked in 2007 which cubic graphs have only one Kempe equivalence class.