Projective freeness and Hermiteness of complex function algebras

TL;DR

This paper investigates conditions under which complex function algebras are projectively free and Hermite, introducing new cohomology criteria and a class of Banach algebras that preserve these properties under tensor products.

Contribution

It provides new cohomology-based conditions for projective freeness and Hermiteness, and introduces a novel class of Banach algebras that maintain these properties.

Findings

New cohomology conditions guarantee projective freeness and Hermiteness.

A class of Banach algebras preserves these properties under tensor products.

Examples include Douglas algebras and algebras of holomorphic functions.

Abstract

The paper studies projective freeness and Hermiteness of algebras of complex-valued continuous functions on topological spaces, Stein algebras, and commutative unital Banach algebras. New sufficient cohomology conditions on the maximal ideal spaces of the algebras are given that guarantee the fulfilment of these properties. The results are illustrated by nontrivial examples. Based on the Borsuk theory of shapes, a new class $\mathscr{C}$ of commutative unital complex Banach algebras is introduced (an analog of the class of local rings in commutative algebra) such that the projective tensor product with algebras in $\mathscr C$ preserves projective freeness and Hermiteness. Some examples of algebras of class $\mathscr{C}$ and of other projective free and Hermite function algebras are assembled. These include, e.g., Douglas algebras, finitely generated algebras of symmetric functions, Bohr-Wiener algebras, algebras of holomorphic semi-almost periodic functions, and algebras of bounded holomorphic functions on Riemann surfaces.