Regular algebras of dimension four associated to coordinate rings of rank-two quadrics

TL;DR

This paper classifies certain four-dimensional algebraic structures called AS-regular algebras that relate to rank-two quadrics, expanding previous classifications to include this specific case.

Contribution

It provides a classification of connected graded quadratic AS-regular algebras of dimension four associated with rank-two quadrics, extending prior work on higher rank quadrics.

Findings

Classification of AS-regular algebras of dimension four linked to rank-two quadrics

Extension of previous classifications to include rank-two cases

Identification of algebraic structures mapping onto coordinate rings of rank-two quadrics

Abstract

In this paper, we classify connected graded quadratic Artin-Schelter regular (AS-regular, henceforth) algebras of global dimension four that have a Hilbert series the same as that of the polynomial ring on four generators and that map onto a twisted homogeneous coordinate ring of a rank-two quadric. A twisted homogeneous coordinate ring is a construction that was defined by Artin, Tate, and Van den Bergh in \cite{ATV1, ATV2, AVdB1990} in the context of the classification of AS-regular algebras of global dimension three. In \cite{SV99,VVr}, the authors classified AS-regular algebras of global dimension four that map onto the twisted homogeneous coordinate ring of a rank-three and a rank-four quadric, respectively. We expand on their work to include the case of coordinate rings of a rank-two quadric.