Homomorphisms to oriented paths
نویسندگان
چکیده
منابع مشابه
Homomorphisms to oriented cycles
We discuss the existence of homomorphisms to oriented cycles and give, for a special class of cycles C, a characterization of those digraphs that admit a homomorphism to C. Our characterization can be used to prove the multiplicativity of these cycles, as well as the membership of the corresponding decision problem in the class NP∩coNP . We also mention a conjecture on the existence of homomorp...
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A homomorphism of an oriented graph G = (V,A) to an oriented graph G = (V , A) is a mapping φ from V to V ′ such that φ(u)φ(v) is an arc in G whenever uv is an arc in G. A homomorphism of G to G is said to be T -preserving for some oriented graph T if for every connected subgraph H of G isomorphic to a subgraph of T , H is isomorphic to its homomorphic image in G. The T -preserving oriented chr...
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We show that the 2-edge-colored chromatic number of a class of simple graphs is bounded if and only if the acyclic chromatic number is bounded for this class. Recently, the CSP dichotomy conjecture has been reduced to the case of 2-edge-colored homomorphism and to the case of 2-vertex-colored homomorphism. Both reductions are rather long and follow the reduction to the case of oriented homomorp...
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ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 1994
ISSN: 0012-365X
DOI: 10.1016/0012-365x(94)90235-6