A Linear Round Lower Bound for Lovasz-Schrijver SDP Relaxations of Vertex Cover

14 years 5 months ago

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We study semideﬁnite programming relaxations of Vertex Cover arising from repeated applications of the LS+ “lift-and-project” method of Lovasz and Schrijver starting from the standard linear programming relaxation. Goemans and Kleinberg prove that after one round of LS+ the integrality gap remains arbitrarily close to 2. Charikar proves an integrality gap of 2 for a stronger relaxation that is, however, incomparable with two rounds of LS+ and is strictly weaker than the relaxation resulting from a constant number of rounds. We prove that the integrality gap remains at least 7/6 − ε after cεn rounds, where n is the number of vertices and cε > 0 is a constant that depends only on ε.

Grant Schoenebeck, Luca Trevisan, Madhur Tulsiani

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