A dichotomy theorem for homomorphism polynomials

  • Authors:
  • Nicolas de Rugy-Altherre

  • Affiliations:
  • Institut de Mathématiques de Jussieu, UMR 7586 CNRS, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France

  • Venue:
  • MFCS'12 Proceedings of the 37th international conference on Mathematical Foundations of Computer Science
  • Year:
  • 2012

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Abstract

In the present paper we show a dichotomy theorem for the complexity of polynomial evaluation. We associate to each graph H a polynomial that encodes all graphs of a fixed size homomorphic to H. We show that this family is computable by arithmetic circuits in constant depth if H has a loop or no edges and that it is hard otherwise (i.e., complete for VNP, the arithmetic class related to #P). We also demonstrate the hardness over ℚ of cut eliminator, a polynomial defined by Bürgisser which is known to be neither VP nor VNP-complete in $\mathbb F_2$, if VP ≠ VNP (VP is the class of polynomials computable by arithmetic circuits of polynomial size).