Isomorphism problems and groups of automorphisms for Ore extensions $K[x][y; f\frac{d}{dx} ]$ (prime characteristic)

Abstract

Let $Λ(f) = K[x][y; f\frac{d}{dx} ]$ be an Ore extension of a polynomial algebra $K[x]$ over an arbitrary field $K$ of characteristic $p>0$ where $f\in K[x]$. For each polynomial $f$, the automorphism group of the algebras $Λ(f)$ is explicitly described. The automorphism group ${\rm Aut}_K(Ł(f))=S\rtimes G_f$ is a semidirect product of two explicit groups where $G_f$ is the {\em eigengroup} of the polynomial $f$ (the set of all automorphisms of $K[x]$ such that $f$ is their common eigenvector). For each polynomial $f$, the eigengroup $G_f$ is explicitly described. It is proven that every subgroup of ${\rm Aut}_K(K[x])$ is the eigengroup of a polynomial. It is proven that the Krull and global dimensions of the algebra $Λ(f)$ are 2. The prime, completely prime, primitive and maximal ideals of the algebra $Λ(f)$ are classified.