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We propose a proof-theoretic approach for gaining evidence that certain parameterized problems are not fixed-parameter tractable. We consider proofs that witness that a given propositional formula… Expand
We survey known results about the complexity of surjective homomorphism problems, studied in the context of related problems in the literature such as list homomorphism, retraction and compaction. In… Expand
We consider a proof (more accurately, refutation) system based on the Sherali-Adams (SA) operator associated with integer linear programming. If F is a CNF contradiction that admits a Resolution… Expand
The universal-algebraic approach has proved a powerful tool in the study of the computational complexity of constraint satisfaction problems (CSPs). This approach has previously been applied to the… Expand
OBJECTIVE
To review changes that occurred in gestational trophoblastic tumor (GTT) patients treated over four decades and to identify factors leading to the changes.
STUDY DESIGN
A retrospective… Expand
For a connected graph G = (V,E), a subset U ⊆ V is called a disconnected cut if U disconnects the graph and the subgraph induced by U is disconnected as well. We show that the problem to test whether… Expand
Hell and Nesetřil proved that the H-colouring problem is NP-complete if, and only if, H is bipartite. In this paper, we investigate the complexity of the quantified H-colouring problem (a restriction… Expand
48th Annual IEEE Symposium on Foundations of…
We propose a proof-theoretic approach for gaining evidence that certain parameterized problems are not fixed-parameter tractable. We consider proofs that witness that a given propositional CNF… Expand
Using a SAT-solver on top of a partial previously-known solution we improve the upper bound of the packing chromatic number of the infinite square lattice from 17 to 15. We discuss the merits of… Expand
We study two containment problems related to the quantified constraint satisfaction problem (QCSP). Firstly, we give a combinatorial condition on finite structures A and B that is necessary and… Expand