English

The poset of king permutations on a cylinder

Combinatorics 2020-06-09 v1

Abstract

A permutation σ=[σ1,,σn]Sn\sigma=[\sigma_1,\dots,\sigma_n] \in S_n is called a {\em cylindrical king permutation} if σi+1σi>1 |\sigma_{i+1}-\sigma_{i}|>1 for each 1in11\leq i \leq n-1 and σ1σn>1|\sigma_1-\sigma_n|>1. The name comes from the the way one can see these permutations as describing locations of nn kings on a chessboard of order n×nn\times n in such a way that (each row and each column contains exactly one king and) no two kings are attacking each other, with the additional condition that a king can move off a certain row and reappear at the beginning of that row. In a recent paper, we dealt with the more general set of 'king permutations' i.e. the ones which satisfy only the first of the two conditions above. This set constitutes a poest under the well known containment relation on permutations. In this article we investigate the sub-poset of the cylindrical king permutations and its structure. We examine those cylindrical king permutations whose downset is as large as possible in the upper ranks. We use a modification of Manhattan distance of the plot of a permutation and some of its applications to the cylindrical context to find a criterion for such a permutation to be kk- prolific. One of our main results is that the maximal gap between two permutations in the poset of cylindrical permutations is 44.

Keywords

Cite

@article{arxiv.2006.04268,
  title  = {The poset of king permutations on a cylinder},
  author = {Eli Bagno and Estrella Eisenberg and Shulamit Reches ans Moriah Sigron},
  journal= {arXiv preprint arXiv:2006.04268},
  year   = {2020}
}