Surjective H-Colouring over Reflexive Digraphs
Surjective H-Colouring over Reflexive Digraphs
The S urjective H-C olouring problem is to test if a given graph allows a vertex-surjective homomorphism to a fixed graph H. The complexity of this problem has been well studied for undirected (partially) reflexive graphs. We introduce endo-triviality , the property of a structure that all of its endomorphisms …