English

Resilience of ranks of higher inclusion matrices

Combinatorics 2017-10-02 v3

Abstract

Let nrs0n \geq r \geq s \geq 0 be integers and F\mathcal{F} a family of rr-subsets of [n][n]. Let Wr,sFW_{r,s}^{\mathcal{F}} be the higher inclusion matrix of the subsets in F{\mathcal F} vs. the ss-subsets of [n][n]. When F\mathcal{F} consists of all rr-subsets of [n][n], we shall simply write Wr,sW_{r,s} in place of Wr,sFW_{r,s}^{\mathcal{F}}. In this paper we prove that the rank of the higher inclusion matrix Wr,sW_{r,s} over an arbitrary field KK is resilient. That is, if the size of F\mathcal{F} is "close" to (nr){n \choose r} then \mboxrankK(Wr,sF)=\mboxrankK(Wr,s)\mbox{rank}_{K}(W_{r,s}^{\mathcal{F}}) = \mbox{rank}_{K}(W_{r,s}), where KK is an arbitrary field. Furthermore, we prove that the rank (over a field KK) of the higher inclusion matrix of rr-subspaces vs. ss-subspaces of an nn-dimensional vector space over Fq\mathbb{F}_q is also resilient if char(K){\rm char}(K) is coprime to qq.

Keywords

Cite

@article{arxiv.1612.08124,
  title  = {Resilience of ranks of higher inclusion matrices},
  author = {Rafael Plaza and Qing Xiang},
  journal= {arXiv preprint arXiv:1612.08124},
  year   = {2017}
}

Comments

17 pages, to appear in Journal of Algebraic Combinatorics