Tight integrality gaps for Lovasz-Schrijver LP relaxations of vertex cover and max cut

  • Authors:
  • Grant Schoenebeck;Luca Trevisan;Madhur Tulsiani

  • Affiliations:
  • UC Berkeley, Berkeley, CA;UC Berkeley, Berkeley, CA;UC Berkeley, Berkeley, CA

  • Venue:
  • Proceedings of the thirty-ninth annual ACM symposium on Theory of computing
  • Year:
  • 2007

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Abstract

We study linear programming relaxations of Vertex Cover and Max Cutarising from repeated applications of the "lift-and-project" method of Lovasz and Schrijver starting from the standard linear programming relaxation. For Vertex Cover, Arora, Bollobas, Lovasz and Tourlakis prove thatthe integrality gap remains at least 2-ε after Ωε(log n) rounds, where n is the number ofvertices, and Tourlakis proves that integrality gap remains at least 1.5-ε after Ω((log n)2) rounds. Fernandez de laVega and Kenyon prove that the integrality gap of Max Cut is at most 12 + ε after any constant number of rounds. (Theirresult also applies to the more powerful Sherali-Adams method. We prove that the integrality gap of Vertex Cover remains at least 2-ε after Ωε (n) rounds, and that theintegrality gap of Max Cut remains at most 1/2 +ε after Ωε(n) rounds.