Hardness of fully dense problems

  • Authors:
  • Nir Ailon;Noga Alon

  • Affiliations:
  • School of Mathematics, Institute for Advanced Study, Princeton, NJ 08540, USA;Schools of Mathematics and Computer Science, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel and IAS, Princeton, NJ 08540, USA

  • Venue:
  • Information and Computation
  • Year:
  • 2007

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Abstract

In the past decade, there has been a stream of work in designing approximation schemes for dense instances of NP-Hard problems. These include the work of Arora, Karger and Karpinski from 1995 and that of Frieze and Kannan from 1996. We address the problem of proving hardness results for (fully) dense problems, which has been neglected despite the fruitful effort put in upper bounds. In this work, we prove hardness results of dense instances of a broad family of CSP problems, as well as a broad family of ranking problems which we refer to as CSP-Rank. Our techniques involve a construction of a pseudorandom hypergraph coloring, which generalizes the well-known Paley graph, recently used by Alon to prove hardness of feedback arc-set in tournaments.