Rational polyhedra and projective lattice-ordered abelian groups with order unit
The paper is devoted to characterizing the finitely generated projectives in the category \(U\) of unital lattice-ordered groups (\(\ell\)-groups), i.e., \(\ell\)-groups with distinguished order unit. The authors solve this problem and show that it is much more complicated than the corresponding problem for \(\ell\)-groups. In fact, in the paper it is shown that various arithmetical, geometric and topological conditions must be imposed to ensure that a finitely presented unital \(\ell\)-group is projectable in \(U\).
scientific article; zbMATH DE number 6072527