Explicit homomorphisms of hexagonal graphs to one vertex deleted Petersen graph∗
نویسندگان
چکیده
The problem of deciding whether an arbitrary graph G has a homomorphism into a given graph H has been widely studied and has turned out to be very difficult. Hell and Nešetril proved that the decision problem is NP-complete unless H is bipartite. We consider a restricted problem where G is an arbitrary triangle-free hexagonal graph and H is a Kneser graph or its induced subgraph. We give an explicit construction which proves that any triangle-free hexagonal graph has a homomorphism into one-vertex deleted Petersen graph. AMS subject classifications: 05C60, 05C15, 05C85, 94C15, 68R10
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