Forest volume decompositions and Abel---Cayley---Hurwitz multinomial expansions

  • Authors:
  • Jim Pitman

  • Affiliations:
  • Department of Statistics, University of California, 367 Evans Hall #3860, Berkeley, California

  • Venue:
  • Journal of Combinatorial Theory Series A
  • Year:
  • 2002

Quantified Score

Hi-index 0.01

Visualization

Abstract

This paper presents a systematic approach to the discovery, interpretation and verification of various extensions of Hurwitz's multinomial identities, involving polynomials defined by sums over all subsets of a finite set. The identities are interpreted as decompositions of forest volumes defined by the enumerator polynomials of sets of rooted labeled forests. These decompositions involve the following basic forest volume formula, which is a refinement of Cayley's multinomial expansion: for R ⊑ S the polynomial enumerating out-degrees of vertices of rooted forests labeled by S whose set of roots is R, with edges directed away from the roots, is (Σxr)(Σxs)|S|-|R|-1.