Posets of width two and skew Young diagrams

Abstract

Let $P$ be a finite poset of width two, i.e., with no three-element antichain. We associate with $P$ a skew Young diagram ${\rm Y}(P)$ and discuss some of the properties of the map ${\rm Y}$. In particular, if we regard ${\rm Y}(P)$ as a poset in a standard way, then the linear extensions of $P$ are in bijection with the order ideals of ${\rm Y}(P)$.

Several people pointed out that most of my results had already been published elsewhere