Actions and identities on set partitions

Eric Marberg

The electronic journal of combinatorics, Tome 19 (2012) no. 1

Résumé

A labeled set partition is a partition of a set of integers whose arcs are labeled by nonzero elements of an abelian group $\mathbb{A}$. Inspired by the action of the linear characters of the unitriangular group on its supercharacters, we define a group action of $\mathbb{A}^n$ on the set of $\mathbb{A}$-labeled partitions of an $(n+1)$-set. By investigating the orbit decomposition of various families of set partitions under this action, we derive new combinatorial proofs of Coker's identity for the Narayana polynomial and its type B analogue, and establish a number of other related identities. In return, we also prove some enumerative results concerning André and Neto's supercharacter theories of type B and D.

Détail

DOI : 10.37236/1992

Classification : 05A18, 05E18
Mots-clés : labeled set partition, Coker's identity for the Narayana polynomial