On the black-box complexity of sperner's lemma

  • Authors:
  • Katalin Friedl;Gábor Ivanyos;Miklos Santha;Yves F. Verhoeven

  • Affiliations:
  • BUTE, Budapest, Hungary;MTA SZTAKI, Budapest, Hungary;CNRS–LRI, UMR 8623, Université Paris XI, Orsay, France;CNRS–LRI, UMR 8623, Université Paris XI, Orsay, France

  • Venue:
  • FCT'05 Proceedings of the 15th international conference on Fundamentals of Computation Theory
  • Year:
  • 2005

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Abstract

We present several results on the complexity of various forms of Sperner's Lemma in the black-box model of computing. We give a deterministic algorithm for Sperner problems over pseudo-manifolds of arbitrary dimension. The query complexity of our algorithm is linear in the separation number of the skeleton graph of the manifold and the size of its boundary. As a corollary we get an $O(\sqrt{n})$ deterministic query algorithm for the black-box version of the problem 2D-SPERNER, a well studied member of Papadimitriou's complexity class PPAD. This upper bound matches the $\Omega(\sqrt{n})$ deterministic lower bound of Crescenzi and Silvestri. The tightness of this bound was not known before. In another result we prove for the same problem an $\Omega(^{4}\sqrt{n})$ lower bound for its probabilistic, and an $\Omega(^{8}\sqrt{n})$ lower bound for its quantum query complexity, showing that all these measures are polynomially related.