Egyptian integral domains

Abstract

The notion of an Egyptian domain (where the analogue of Egyptian fractions works appropriately), first explored by Guerrieri-Loper-Oman, is extended to the more general notions of generically and locally Egyptian domains. Results from the previous paper are extended, as well as reinterpreted in the new expanded context. It is shown that localizations of polynomial rings are typically Egyptian, that positive semigroup-graded domains are not Egyptian, and that affine semigroup rings are not Egyptian unless the semigroup is a group. However, any finitely generated algebra over a field or $\mathbb Z$ is shown to be locally Egyptian. It is further shown that if $R$ is a pullback of $S$, then $R$ is Egyptian if and only if $S$ is.