Heterochromatic Geometric Transversals of Convex sets (2212.14091v5)

Abstract: An infinite sequence of sets $\left{B_{n}\right}{n\in\mathbb{N}}$ is said to be a heterochromatic sequence from an infinite sequence of families $\left{ \mathcal{F}{n} \right}{n \in \mathbb{N}}$, if there exists a strictly increasing sequence of natural numbers $\left{ i{n}\right}{n \in \mathbb{N}}$ such that for all $n \in \mathbb{N}$ we have $B{n} \in \mathcal{F}{i{n}}$. In this paper, we have proved that if for each $n\in\mathbb{N}$, $\mathcal{F}n$ is a family of {\em nicely shaped} convex sets in $\mathbb{R}^d$ such that each heterochromatic sequence $\left{B{n}\right}{n\in\mathbb{N}}$ from $\left{ \mathcal{F}{n} \right}{n \in \mathbb{N}}$ contains at least $k+2$ sets that can be pierced by a single $k$-flat ($k$-dimensional affine space) then all but finitely many families in $\left{\mathcal{F}{n}\right}_{n\in \mathbb{N}}$ can be pierced by finitely many $k$-flats. This result can be considered as a {\em countably colorful} generalization of the $(\aleph_0, k+2)$-theorem proved by Keller and Perles (Symposium on Computational Geometry 2022). We have also established the tightness of our result by proving a number of no-go theorems.