Maximum linearizations of lower sets in ${\mathbb{N}}^m$ with application to monomial ideals

Abstract

We compute the type (maximum linearization) of the well partial order of bounded lower sets in ${\mathbb{N}}^m$, ordered under inclusion, and find it is $\ddot{I}{‰}^{\ddot{I}{‰}^{m-1}}$. Moreover we compute the type of the set of all lower sets in ${\mathbb{N}}^m$, a topic studied by Aschenbrenner and Pong, and find that it is equal to \[ ω^{\sum_{k=1}^{m} ω^{m-k}\binom{m}{k-1} }+ 1. \] As a consequence we deduce corresponding bounds on effectively given sequences of monomial ideals in $F[X,Y]$ where $F$ is a field.

10 pages