In the above example, each vertex of H has exactly 2 preimages in C. Hence H is a 2-fold cover or a double cover of C.
For any graph G, it is possible to construct the bipartite double cover of G, which is a bipartite graph and a double cover of G. The bipartite double cover of G is the tensor product of graphs G × K2:
If G is already bipartite, its bipartite double cover consists of two disjoint copies of G. A graph may have many different double covers other than the bipartite double cover.
Read more about this topic: Covering Graph
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