Quasi-Randomness and Algorithmic Regularity for Graphs with General Degree Distributions

  • Authors:
  • Noga Alon;Amin Coja-Oghlan;Hiêp Hàn;Mihyun Kang;Vojtěch Rödl;Mathias Schacht

  • Affiliations:
  • noga@math.tau.ac.il;A.Coja-Oghlan@warwick.ac.uk;hhan@informatik.hu-berlin.de;kang@math.tu-berlin.de;rodl@mathcs.emory.edu;schacht@math.uni-hamburg.de

  • Venue:
  • SIAM Journal on Computing
  • Year:
  • 2010

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Abstract

We deal with two intimately related subjects: quasi-randomness and regular partitions. The purpose of the concept of quasi-randomness is to express how much a given graph “resembles” a random one. Moreover, a regular partition approximates a given graph by a bounded number of quasi-random graphs. Regarding quasi-randomness, we present a new spectral characterization of low discrepancy, which extends to sparse graphs. Concerning regular partitions, we introduce a concept of regularity that takes into account vertex weights, and show that if $G=(V,E)$ satisfies a certain boundedness condition, then $G$ admits a regular partition. In addition, building on the work of Alon and Naor [Proceedings of the 36th ACM Symposium on Theory of Computing (STOC), Chicago, IL, ACM, New York, 2004, pp. 72-80], we provide an algorithm that computes a regular partition of a given (possibly sparse) graph $G$ in polynomial time. As an application, we present a polynomial time approximation scheme for MAX CUT on (sparse) graphs without “dense spots.”