Towards a trichotomy for quantified H-coloring

  • Authors:
  • Barnaby Martin;Florent Madelaine

  • Affiliations:
  • Department of Computer Science, University of Durham, U.K.;Department of Computer Science, University of Durham, U.K.

  • Venue:
  • CiE'06 Proceedings of the Second conference on Computability in Europe: logical Approaches to Computational Barriers
  • Year:
  • 2006

Quantified Score

Hi-index 0.00

Visualization

Abstract

Hell and Nešetřil 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 of the quantified constraint satisfaction problem to undirected graphs). We introduce this problem using a new two player colouring game. We prove that the quantified H-colouring problem is: 1. tractable, if H is bipartite; 2. NP-complete, if H is not bipartite and not connected; and, 3. Pspace-complete, if H is connected and has a unique cycle, which is of odd length. We conjecture that the last case extends to all non-bipartite connected graphs.