Exponential Dowling structures

  • Authors:
  • Richard Ehrenborg;Margaret A. Readdy

  • Affiliations:
  • Department of Mathematics, University of Kentucky, Lexington, KY 40506, USA;Department of Mathematics, University of Kentucky, Lexington, KY 40506, USA

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2009

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Abstract

The notion of exponential Dowling structures is introduced, generalizing Stanley's original theory of exponential structures. Enumerative theory is developed to determine the Mobius function of exponential Dowling structures, including a restriction of these structures to elements whose types satisfy a semigroup condition. Stanley's study of permutations associated with exponential structures leads to a similar vein of study for exponential Dowling structures. In particular, for the extended r-divisible partition lattice we show that the Mobius function is, up to a sign, the number of permutations in the symmetric group on rn+k elements having descent set {r,2r,...,nr}. Using Wachs' original EL-labeling of the r-divisible partition lattice, the extended r-divisible partition lattice is shown to be EL-shellable.