Extremal properties of regular and affine generalized m-gons as tactical configurations

  • Authors:
  • V. A. Ustimenko;A. J. Woldar

  • Affiliations:
  • Department of Mathematics and Statistics, Sultan Qaboos University, Muscat, Sultanate of Oman;Department of Mathematical Sciences, Villanova University, Villanova, PA

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2003

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Abstract

The purpose of this paper is to derive bounds on the sizes of tactical configurations of large girth which provide analogues to the well-known bounds on the sizes of graphs of large girth. Let exα(v,g) denote the greatest number of edges in a tactical configuration of order v, bidegree a, aα and girth at least g. We establish the upper bound exα (v,g) = 0(v1+1/τ), where τ = 1/4(α + 1)g -1 for g = 0(mod 4) and τ = 1/4(α + 1)g + ½(α - 3) for g ≡ = 2(mod 4). We further demonstrate this bound to be sharp for the regular and affine generalized m-gons but not for the nonregular generalized m-gons. Finally, we derive lower bounds on exα(v, g) via explicit group theoretic constructions.