Logical compactness and constraint satisfaction problems

  title={Logical compactness and constraint satisfaction problems},
  author={Danny Rorabaugh and Claude Tardif and David L. Wehlau},
  journal={Log. Methods Comput. Sci.},
We investigate a correspondence between the complexity hierarchy of constraint satisfaction problems and a hierarchy of logical compactness hypotheses for finite relational structures. It seems that the harder a constraint satisfaction problem is, the stronger the corresponding compactness hypothesis is. At the top level, the NP-complete constraint satisfaction problems correspond to compactness hypotheses that are equivalent to the ultrafilter axiom in all the cases we have investigated. At… 

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