The Complexity of Approximately Counting Tree Homomorphisms
نویسندگان
چکیده
منابع مشابه
Complexity of Tree Homomorphisms
For a fixed oriented tree T, we consider the complexity of deciding whether or not a given digraph G is homomorphic to T. It was shown by Gutjahr, Woeginger and Welzl that there exist trees T for which this homomorphism problem is NP-complete. However, it seems difficult to decide just which trees T yield NP-complete homomorphism problems. In this paper, we first identify a class of simple tree...
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The problem of counting homomorphisms from a general graph G to a fixed graph H is a natural generalisation of graph colouring, with important applications in statistical physics. The problem of deciding whether any homomorphism exists was considered by Hell and Nešetřil. They showed that decision is NPcomplete unless H has a loop or is bipartite; otherwise it is in P. We consider the problem o...
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We close a gap in the proof of Theorem 4.1 in our paper “The complexity of counting graph homomorphisms” [Random Structures and Algorithms 17 (2000), 260– 289]. Our paper [2] analysed the complexity of counting graph homomorphisms from a given graph G into a fixed graph H. This problem was called #H. A crucial step in our argument, Theorem 4.1, was to prove that the counting problem #H is #P -c...
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ژورنال
عنوان ژورنال: ACM Transactions on Computation Theory
سال: 2014
ISSN: 1942-3454,1942-3462
DOI: 10.1145/2600917