如果空间图G的两个嵌入可以由自交叉变换和空间合痕相互转化,则称这两个嵌入是边同伦的.将证明:空间图D3的任意两个空间嵌入f和g是边同伦的当且仅当α(f)=α(g),并且给出了D3的边同伦分类列表.
Two embeddings of a spatial graph G are said to be edge - homotopic if they are transformed into each other by self - crossings and ambient isotopies. It is shown that two spatial embeddings of D3 are edge - homotopic if and only if they have the same α - invariant. Then a complete list of edge - homotopy classes of D3 is given.