English

Combinatorics of $q$-Mahonian numbers of type $B$ and log-concavity

Combinatorics 2024-08-06 v1

Abstract

This paper is a continuation of earlier work of Arslan \cite{Ars}, who introduced the Mahonian number of type BB by using a new statistic on the hyperoctahedral group BnB_{n}, in response to questions he suggested in his paper entitled "{\it A combinatorial interpretation of Mahonian numbers of type BB}" published in arXiv:2404.05099v1. We first give the Knuth-Netto formula and generating function for the subdiagonals on or below the main diagonal of the Mahonian numbers of type BB, then its combinatorial interpretations by lattice path/partition and tiling. Next, we propose a qq-analogue of Mahonian numbers of type BB by using a new statistics on the permutations of the hyperoctahedral group BnB_n that we introduced, then we study their basic properties and their combinatorial interpretations by lattice path/partition and tiling. Finally, we prove combinatorially that the qq-analogue of Mahonian numbers of type BB form a strongly qq-log-concave sequence of polynomials in kk, which implies that the Mahonian numbers of type BB form a log-concave sequence in kk and therefore unimodal.

Keywords

Cite

@article{arxiv.2408.02424,
  title  = {Combinatorics of $q$-Mahonian numbers of type $B$ and log-concavity},
  author = {Ali Kessouri and Moussa Ahmia and Hasan Arslan and Salim Mesbahi},
  journal= {arXiv preprint arXiv:2408.02424},
  year   = {2024}
}