Almost $t$-intersecting families for vector spaces

Dehai Liu, Kaishun Wang, Tian Yao

Published 2024-06-09Version 1

Let $V$ be a finite dimensional vector space over a finite field. A family $\mathcal{F}$ consisting of $k$-subspcaes of $V$ is called almost $t$-intersecting if for each $F\in \mathcal{F}$ there is at most one $F^{\prime}\in \mathcal{F}$ with $\dim(F\cap F^{\prime})\leq t-1$. In this paper, we determine the maximum value and the extremal structure of almost $t$-intersecting families. We also solve the same problems for almost $t$-intersecting families but not $t$-intersecting.