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CORR
2010
Springer

Dichotomy for tree-structured trigraph list homomorphism problems

13 years 10 months ago
Dichotomy for tree-structured trigraph list homomorphism problems
Trigraph list homomorphism problems (also known as list matrix partition problems) have generated recent interest, partly because there are concrete problems that are not known to be polynomial time solvable or NP-complete. Thus while digraph list homomorphism problems enjoy dichotomy (each problem is NP-complete or polynomial time solvable), such dichotomy is not necessarily expected for trigraph list homomorphism problems. However, in this paper, we identify a large class of trigraphs for which list homomorphism problems do exhibit a dichotomy. They consist of trigraphs with a tree-like structure, and, in particular, include all trigraphs whose underlying graphs are trees. In fact, we show that for these tree-like trigraphs, the trigraph list homomorphism problem is polynomially equivalent to a related digraph list homomorphism problem. We also describe a few examples illustrating that our conditions defining the tree-like trigraphs are necessary at least for some trigraphs. Key wor...
Tomás Feder, Pavol Hell, David G. Schell, J
Added 09 Dec 2010
Updated 09 Dec 2010
Type Journal
Year 2010
Where CORR
Authors Tomás Feder, Pavol Hell, David G. Schell, Juraj Stacho
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