Construction of lattice orders on the semigroup ring of a positive rooted monoid

Abstract

Lattice orders on the semigroup ring of a positive rooted monoid are constructed, and it is shown how to make the monoid ring into a lattice-ordered ring with squares positive in various ways. It is proved that under certain conditions these are all of the lattice orders that make the monoid ring into a lattice-ordered ring. In particular, all of the partial orders on the polynomial ring A [ x ] in one positive variable are determined for which the ring is not totally ordered but is a lattice-ordered ring with the property that the square of every element is positive. In the last section some basic properties of d -elements are considered, and they are used to characterize lattice-ordered division rings that are quadratic extensions of totally ordered division rings.