Root of unity quantum cluster algebras and Cayley-Hamilton algebras

TL;DR

This paper demonstrates that many root of unity quantum cluster algebras are maximal orders and Cayley-Hamilton algebras, providing explicit formulas and new methods based on cluster algebra theory.

Contribution

It introduces a novel approach using cluster algebra techniques to establish maximal order and Cayley-Hamilton structures in root of unity quantum cluster algebras.

Findings

Root of unity quantum cluster algebras are maximal orders.

Explicit formula for the reduced trace of these algebras.

Classification of monomial subalgebras that are Cayley-Hamilton and maximal orders.

Abstract

We prove that large classes of algebras in the framework of root of unity quantum cluster algebras have the structures of maximal orders in central simple algebras and Cayley-Hamilton algebras in the sense of Procesi. We show that every root of unity upper quantum cluster algebra is a maximal order and obtain an explicit formula for its reduced trace. Under mild assumptions, inside each such algebra we construct a canonical central subalgebra isomorphic to the underlying upper cluster algebra, such that the pair is a Cayley-Hamilton algebra; its fully Azumaya locus is shown to contain a copy of the underlying cluster $\mathcal{A}$-variety. Both results are proved in the wider generality of intersections of mixed quantum tori over subcollections of seeds. Furthermore, we prove that all monomial subalgebras of root of unity quantum tori are Cayley-Hamilton algebras and classify those ones that are maximal orders. Arbitrary intersections of those over subsets of seeds are also proved to be Cayley-Hamilton algebras. Previous approaches to constructing maximal orders relied on filtration and homological methods. We use new methods based on cluster algebras.