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A Dichotomy Theorem for Nonuniform CSPs

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TLDR
In this paper, the authors confirm the Dichotomy Conjecture for the non-uniform CSP, which states that for every constraint language \Gm the problem is either solvable in polynomial time or is NP-complete.
Abstract
In a non-uniform Constraint Satisfaction problem CSP(Γ), where G is a set of relations on a finite set A, the goal is to find an assignment of values to variables subject to constraints imposed on specified sets of variables using the relations from Γ. The Dichotomy Conjecture for the non-uniform CSP states that for every constraint language \Gm the problem CSP(Γ) is either solvable in polynomial time or is NP-complete. It was proposed by Feder and Vardi in their seminal 1993 paper. In this paper we confirm the Dichotomy Conjecture.

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Structure Meets Power Workshop

Anuj Dawar
TL;DR: In this paper , Chen et al. investigated the expressive power of query algorithms in identifying classes of graphs using a fixed number of left homomorphism counts and compared it with the expression of the data join, the most important construct of a query language.
Journal ArticleDOI

A Tetrachotomy of Ontology-Mediated Queries with a Covering Axiom

TL;DR: In this article , the problem of determining the data complexity of answering queries mediated by description logic ontologies and constructing their optimal rewritings to standard database queries is considered, which is known to be computationally very complex in general, with no explicit syntactic characterisations available.
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Boolean symmetric vs. functional PCSP dichotomy

TL;DR: A dichotomy is established for PCSP( A, B), where A is Boolean and symmetric and B is functional (on a domain of any size), and it is shown that the combined basic linear programming relaxation (BLP) and the affine integer Programming relaxation (AIP) of Brakensiek et al. is no more powerful than the (in general strictly weaker) AIP relaxation of Brakeniek and Guruswami.
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Accessible set endofunctors are universal

Libor Barto
TL;DR: It was shown in this article that every concretizable category can be fully embedded into the category of accessible set functors and natural transformations, and that every set functor can be embedded in the class of natural transformations.
Posted Content

The lattice of clones of self-dual operations collapsed

TL;DR: In this article, the existence of clones of self-dual operations on a three-element set was shown to be a property of primitive positive constructability, i.e., there exists a minor-preserving map from the polymorphism clone of a finite structure to the corresponding clone if and only if there is a primitive positive construction of the clone in the structure.
References
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Proceedings ArticleDOI

The complexity of satisfiability problems

TL;DR: An infinite class of satisfiability problems is considered which contains these two particular problems as special cases, and it is shown that every member of this class is either polynomial-time decidable or NP-complete.
Journal ArticleDOI

The Computational Structure of Monotone Monadic SNP and Constraint Satisfaction: A Study through Datalog and Group Theory

TL;DR: This paper isolates a class (of problems specified by) "monotone monadic SNP without inequality" which may exhibit a dichotomy, and explains the placing of all these restrictions by showing, essentially using Ladner's theorem, that classes obtained by using only two of the above three restrictions do not show this dichotomy.
Journal ArticleDOI

On the complexity of H -coloring

TL;DR: The natural conjecture, formulated in several sources, asserts that the H-coloring problem is NP-complete for any non-bipartite graph H, and a proof of this conjecture is given.
Journal ArticleDOI

Classifying the Complexity of Constraints Using Finite Algebras

TL;DR: It is shown that any set of relations used to specify the allowed forms of constraints can be associated with a finite universal algebra and how the computational complexity of the corresponding constraint satisfaction problem is connected to the properties of this algebra is explored.
Journal ArticleDOI

Undirected connectivity in log-space

TL;DR: A deterministic, log-space algorithm that solves st-connectivity in undirected graphs and implies a way to construct in log- space a fixed sequence of directions that guides a deterministic walk through all of the vertices of any connected graph.
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