直径为2与3的符号图的上可嵌入

The Upper Embeddable of Signed Graphs with Diameter two and three

设Σ=（G,σ）是直径为2和3连通的简单符号图,G是Σ的基础图.若Σ扭转等价Δ2-图或Δ3-图,则Σ的Betti亏数ξ（Σ）=2,否则Σ是上可嵌入的,即ξ（Σ）≤1.

Let Σ =（G,σ） be a simple signed graph with diameter two and three,G is the underlying graph of Σ. If Σ is switched to be equivalent of Δ2-graph or Δ3-graph,then betti deficiency number ξ（Σ） = 2,otherwise Σ is upper-embeddable,i.e.,ξ（Σ） ≤ 1.