Sparse universal graphs for bounded-degree graphs

  • Authors:
  • Noga Alon;Michael Capalbo

  • Affiliations:
  • Schools of Mathematics and Computer Science, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel/ IAS, Princeton, NJ 08540;DIMACS, Rutgers University, Piscataway, NJ

  • Venue:
  • Random Structures & Algorithms
  • Year:
  • 2007

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Abstract

Let ℋ be a family of graphs. A graph T isℋ-universal if it contains a copy of eachHεℋ as a subgraph. Letℋ(k,n) denote the family of graphs on nvertices with maximum degree at most k. For all positiveintegers k and n, we construct anℋ(k,n)-universal graph T withOk(n2-2/klog4/kn)edges and exactly n vertices. The number of edges is almostas small as possible, as Ω(n2-2/k) is alower bound for the number of edges in any such graph. Theconstruction of T is explicit, whereas the proof ofuniversality is probabilistic and is based on a novel graphdecomposition result and on the properties of random walks onexpanders. © 2006 Wiley Periodicals, Inc. Random Struct. Alg.,2007