Expansion Of Product Replacement Graphs

  • Authors:
  • Alexander Gamburd;Igor Pak

  • Affiliations:
  • Department of Mathematics, Stanford University, Stanford, CA 94305, USA;Department of Mathematics, MIT, Cambridge, MA 02139, USA

  • Venue:
  • Combinatorica
  • Year:
  • 2006

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Abstract

We establish a connection between the expansion coefficient of the product replacement graph Γk(G) and the minimal expansion coefficient of a Cayley graph of G with k generators. In particular, we show that the product replacement graphs Γk(PSL(2,p)) form an expander family, under assumption that all Cayley graphs of PSL(2,p), with at most k generators are expanders. This gives a new explanation of the outstanding performance of the product replacement algorithm and supports the speculation that all product replacement graphs are expanders [42,52].