# The lattice structure of sets of surjective hyper-operations

Martin, Barnaby
(2010)
*The lattice structure of sets of surjective hyper-operations.*
In:
Principles and practice of constraint programming – CP 2010.
Lecture Notes in Computer Science
(6308)
.
Springer-Verlag, pp. 368-382.
ISBN 9783642153952.
(doi:10.1007/978-3-642-15396-9_31)

## Abstract

[NB some mathematical symbols may have been omitted from this abstract due to software limitations]. We study the lattice structure of sets (monoids) of surjective hyper-operations on an n-element domain. Through a Galois connection, these monoids form the algebraic counterparts to sets of relations closed under definability in positive first-order (fo) logic without equality. Specifically, for a countable set of relations (forming the finite-domain structure) B , the set of relations definable over B in positive fo logic without equality consists of exactly those relations that are invariant under the surjective hyper-endomorphisms (shes) of B . The evaluation problem for this logic on a fixed finite structure is a close relative of the quantified constraint satisfaction problem (QCSP).

We study in particular an inverse operation that specifies an automorphism of our lattice. We use our results to give a dichotomy theorem for the evaluation problem of positive fo logic without equality on structures that are she-complementative, i.e. structures B whose set of shes is closed under inverse. These problems turn out either to be in L or to be Pspace-complete.

We go on to apply our results to certain digraphs. We prove that the evaluation of positive fo without equality on a semicomplete digraph is always Pspace-complete. We go on to prove that this problem is NP-hard for any graph of diameter at least 3. Finally, we prove a tetrachotomy for antireflexive and reflexive graphs, modulo a known conjecture as to the complexity of the QCSP on connected non-bipartite graphs. Specifically, these problems are either in L, NP-complete, co-NP-complete or Pspace-complete.

Item Type: | Book Section |
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Additional Information: | Online ISBN: 9783642153969 |

Research Areas: | A. > School of Science and Technology > Computer Science A. > School of Science and Technology > Computer Science > Foundations of Computing group |

Item ID: | 9754 |

Useful Links: | |

Depositing User: | Devika Mohan |

Date Deposited: | 01 Feb 2013 15:54 |

Last Modified: | 24 Apr 2018 15:32 |

URI: | https://eprints.mdx.ac.uk/id/eprint/9754 |

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