English

$s$-almost $t$-intersecting families for vector spaces

Combinatorics 2024-12-18 v3

Abstract

Let VV be a finite dimensional vector space over a finite field, and F\mathcal{F} a family consisting of kk-subspaces of VV. The family F\mathcal{F} is called tt-intersecting if dim(F1F2)t\dim(F_{1}\cap F_{2})\geq t for any F1,F2FF_{1}, F_{2}\in \mathcal{F}. We say F\mathcal{F} is ss-almost tt-intersecting if for each FFF\in \mathcal{F} there are at most ss members FF^{\prime} of F\mathcal{F} such that dim(FF)<t\dim(F\cap F^{\prime})<t. In this paper, we prove that ss-almost tt-intersecting families with maximum size are tt-intersecting. We also consider ss-almost tt-intersecting families which are not tt-intersecting, and characterize such families with maximum size for (s,t)(1,1)(s,t)\neq(1,1). The result for 11-almost 11-intersecting families provided by Shan and Zhou is generalized.

Keywords

Cite

@article{arxiv.2406.05840,
  title  = {$s$-almost $t$-intersecting families for vector spaces},
  author = {Lijun Ji and Dehai Liu and Kaishun Wang and Tian Yao and Shuhui Yu},
  journal= {arXiv preprint arXiv:2406.05840},
  year   = {2024}
}
R2 v1 2026-06-28T16:58:51.754Z