Published online by Cambridge University Press: 20 November 2018
An integral domain $R$ is IDPF (Irreducible Divisors of Powers Finite) if, for every non-zero element
$a$ in
$R$, the ascending chain of non-associate irreducible divisors in
$R$ of
${{a}^{n}}$ stabilizes on a finite set as
$n$ ranges over the positive integers, while
$R$ is atomic if every non-zero element that is not a unit is a product of a finite number of irreducible elements (atoms). A ring extension
$S$ of
$R$ is a root extension or radical extension if for each
$s$ in
$S$, there exists a natural number
$n\left( s \right)$ with
${{s}^{n\left( s \right)}}$ in
$R$. In this paper it is shown that the ascent and descent of the IDPF property and atomicity for the pair of integral domains
$\left( R,\,S \right)$ is governed by the relative sizes of the unit groups
$\text{U}\left( R \right)$ and
$\text{U}\left( S \right)$ and whether
$S$ is a root extension of
$R$. The following results are deduced from these considerations: An atomic IDPF domain containing a field of characteristic zero is completely integrally closed. An affine domain over a field of characteristic zero is IDPF if and only if it is completely integrally closed. Let
$R$ be a Noetherian domain with integral closure
$S$. Suppose the conductor of
$S$ into
$R$ is non-zero. Then
$R$ is IDPF if and only if
$S$ is a root extension of
$R$ and
$\text{U}\left( S \right)/\text{U}\left( R \right)$ is finite.