Adjoint functors and tree duality - Inria - Institut national de recherche en sciences et technologies du numérique Access content directly
Journal Articles Discrete Mathematics and Theoretical Computer Science Year : 2009

Adjoint functors and tree duality

Abstract

A family T of digraphs is a complete set of obstructions for a digraph H if for an arbitrary digraph G the existence of a homomorphism from G to H is equivalent to the non-existence of a homomorphism from any member of T to G. A digraph H is said to have tree duality if there exists a complete set of obstructions T consisting of orientations of trees. We show that if H has tree duality, then its arc graph delta H also has tree duality, and we derive a family of tree obstructions for delta H from the obstructions for H. Furthermore we generalise our result to right adjoint functors on categories of relational structures. We show that these functors always preserve tree duality, as well as polynomial CSPs and the existence of near-unanimity functions.
Fichier principal
Vignette du fichier
987-4374-2-PB.pdf (172.78 Ko) Télécharger le fichier
Origin : Files produced by the author(s)
Loading...

Dates and versions

hal-00988207 , version 1 (07-05-2014)

Identifiers

Cite

Jan Foniok, Claude Tardif. Adjoint functors and tree duality. Discrete Mathematics and Theoretical Computer Science, 2009, Vol. 11 no. 2 (2), pp.97--109. ⟨10.46298/dmtcs.458⟩. ⟨hal-00988207⟩

Collections

TDS-MACS
66 View
667 Download

Altmetric

Share

Gmail Facebook X LinkedIn More