The Aharoni--Korman conjecture is false

Abstract

A poset $P$ is said to satisfy the finite antichain condition, or FAC, if it has no infinite antichain. It was conjectured by Aharoni and Korman in 1992 that any FAC poset $P$ possesses a chain $C$ and a partition into antichains such that $C$ meets every antichain of the partition. In this work we provide a counterexample to this conjecture, demonstrating that it is false. We also discuss variations of the conjecture which may yet be true.