Testing Expansion in Bounded-Degree Graphs

  • Authors:
  • Artur Czumaj;Christian Sohler

  • Affiliations:
  • -;-

  • Venue:
  • FOCS '07 Proceedings of the 48th Annual IEEE Symposium on Foundations of Computer Science
  • Year:
  • 2007

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Abstract

We consider the problem of testing expansion in bounded degree graphs. We focus on the notion of vertex-expansion: an \alpha- \expander is a graph G = (V; E) in which every subset U \subseteq V of at most \left| V \right|/2 vertices has a neighborhood of size at least \alpha\cdot \left| U \right|. Our main result is that one can distinguish good expanders from graphs that are far from being weak expanders in time \mathop O\limits^\~ (\sqrt n ). We prove that the property testing algorithm proposed by Goldreich and Ron (2000) with appropriately set parameters accepts every \alpha- \exp ander with probability at least \frac{2} {3} and rejects every graph that is\in- far from an \alpha * - \exp ander with probability at least \frac{2} {3}, where \alpha * = \Theta (\frac{{\alpha ^2 }} {{d^2 \log (n/ \in )}}) and d is the maximum degree of the graphs. The algorithm assumes the bounded- degree graphs model with adjacency list graph representation and its running time is O(\frac{{d^2 \sqrt n \log (n/ \in )}} {{\alpha ^2\in ^3 }}).