Non-integrally closed Kronecker function rings and integral domains with a unique minimal overring

Abstract

It is well-known that an integrally closed domain $D$ can be express as the intersection of its valuation overrings but, if $D$ is not a Prüfer domain, the most of valuation overrings of $D$ cannot be seen as localizations of $D$. The Kronecker function ring of $D$ is a classical construction of a Prüfer domain which is an overring of $D[t]$, and its localizations at prime ideals are of the form $V(t)$ where $V$ runs through the valuation overrings of $D$. This fact can be generalized to arbitrary integral domains by expressing them as intersections of overrings which admit a unique minimal overring. In this article we first continue the study of rings admitting a unique minimal overring extending known results obtained in the 70's and constructing examples where the integral closure is very far from being a valuation domain. Then we extend the definition of Kronecker function ring to the non-integrally closed setting by studying intersections of Nagata rings of the form $A(t)$ for $A$ an integral domain admitting a unique minimal overring.

30 pages, comments are welcome