The Grothendieck constant of random and pseudo-random graphs

  • Authors:
  • Noga Alon;Eli Berger

  • Affiliations:
  • Schools of Mathematics and Computer Science, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel;Department of Mathematics, University of Haifa, Haifa 31905, Israel

  • Venue:
  • Discrete Optimization
  • Year:
  • 2008

Quantified Score

Hi-index 0.00

Visualization

Abstract

The Grothendieck constant of a graph G=(V,E) is the least constant K such that for every matrix A:VxV-R, maxf:V-S^|^V^|^-^1@?{u,v}@?EA(u,v)@?@?Kmax@e:V-{-1,+1}@?{u,v}@?EA(u,v)@?@e(u)@e(v). The investigation of this parameter, introduced in [N. Alon, K. Makarychev, Y. Makarychev, A. Naor, Quadratic forms on graphs, in: Proc. of the 37th ACM STOC, ACM Press, Baltimore, 2005, pp. 486-493 (Also: Invent. Math. 163 (2006) 499-522)], is motivated by the algorithmic problem of maximizing the quadratic form @?"{"u","v"}"@?"EA(u,v)@e(u)@e(v) over all @e:V-{-1,1}, which arises in the study of correlation clustering and in the investigation of the spin glass model. In the present note we show that for the random graph G(n,p) the value of this parameter is, almost surely, @Q(log(np)). This settles a problem raised in [N. Alon, K. Makarychev, Y. Makarychev, A. Naor, Quadratic forms on graphs, in: Proc. of the 37th ACM STOC, ACM Press, Baltimore, 2005, pp. 486-493 (Also: Invent. Math. 163 (2006) 499-522)]. We also obtain a similar estimate for regular graphs in which the absolute value of each nontrivial eigenvalue is small.