Recent advances in arrow relations and traces of sets

Abstract

The arrow relation, a central concept in extremal set theory, captures quantitative relationships between families of sets and their traces. Formally, the arrow relation $(n,m)\to (a,b)$ signifies that for any family $\mathcal{F}\subseteq 2^{[n]}$ with $|\mathcal{F}|⩾m$, there exists an $a$-element subset $T\subseteq [n]$ such that the trace ${\mathcal{F}}_{|T}=\{F\cap T:F\in \mathcal{F}\}$ contains at least $b$ distinct sets. This survey highlights recent progress on a variety of problems and results connected to arrow relations. We explore diverse topics, broadly categorized by different extremal perspectives on these relations, offering a cohesive overview of the field.

A survey contributed to the volume for the conference Summit280