"Exponential Dowling Structures"

Richard Ehrenborg
University of Kentucky

Monday, February 11, 2008
4:00 pm, 112 Patterson Office Tower

Abstract:

We introduce exponential Dowling structures, 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. In particular, for the extended r-divisible partition lattice we show 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}.

This is joint work with Margaret Readdy.