English

Property $(\diamond)$ for Ore extensions of small Krull dimension

Rings and Algebras 2025-05-28 v1

Abstract

This paper is a continuation of a project to determine which skew polynomial algebras S=R[θ;α]S = R[\theta; \alpha] satisfy property ()(\diamond), namely that the injective hull of every simple SS-module is locally artinian, where kk is a field, RR is a commutative noetherian kk-algebra, and α\alpha is a kk-algebra automorphism of RR. Earlier work (which we review) and further analysis done here leads us to focus on the case where SS is a primitive domain and RR has Krull dimension 1 and contains an uncountable field. Then we show first that if Spec(R)|\mathrm{Spec}(R)| is infinite then SS does not satisfy ()(\diamond). Secondly we show that when R=k[X]<X>R = k[X]_{<X>} and α(X)=qX\alpha (X) = qX where qk{0}q \in k \setminus \{0\} is not a root of unity then SS does not satisfy ()(\diamond). This is in complete contrast to our earlier result that, when R=k[[X]]R = k[[X]] and α\alpha is an arbitrary kk-algebra automorphism of infinite order, SS satisfies ()(\diamond). A number of open questions are stated.

Keywords

Cite

@article{arxiv.2403.09239,
  title  = {Property $(\diamond)$ for Ore extensions of small Krull dimension},
  author = {Ken Brown and Paula A. A. B. Carvalho and Jerzy Matczuk},
  journal= {arXiv preprint arXiv:2403.09239},
  year   = {2025}
}

Comments

15pages, comments welcome