On the Laplacian Eigenvalues of Gn,p

  • Authors:
  • Amin Coja-Oghlan

  • Affiliations:
  • Carnegie Mellon University, Department of Mathematical Sciences, Pittsburgh, PA 15213, USA (e-mail: coja@informatik.hu-berlin.de)

  • Venue:
  • Combinatorics, Probability and Computing
  • Year:
  • 2007

Quantified Score

Hi-index 0.00

Visualization

Abstract

We investigate the Laplacian eigenvalues of sparse random graphsGnp. We show that in the case that the expected degree d= (n-1)p is bounded, the spectral gap of thenormalized Laplacian ℒ(Gn,p) iso(1). Nonetheless, w.h.p. G = Gnp has a largesubgraph core(G) such that the spectral gap ofℒ(core(G)) is as large as 1-O(d1/2). We derive similar results regarding the spectrumof the combinatorial Laplacian L(Gnp). Thepresent paper complements the work of Chung, Lu and Vu [8] on theLaplacian spectra of random graphs with given expected degreesequences. Applied to Gnp, their results imply that inthe dense case d ≥ ln2n the spectral gap ofℒ(Gn,p)is 1-O(d1/2) w.h.p.