Structure theory of homologically trivial and annihilator locally C*-algebras

TL;DR

This paper characterizes the structure of certain homologically trivial locally C*-algebras, showing their relation to elementary C*-algebras, annihilator properties, and biprojective and superbiprojective structures.

Contribution

It provides a complete characterization of homologically trivial locally C*-algebras, including conditions for projectivity, annihilator properties, and structure of biprojective and superbiprojective algebras.

Findings

All irreducible Hermitian modules are projective iff A is a sum of elementary C*-algebras.

Characterization of annihilator σ-C*-algebras.

Every superbiprojective locally C*-algebra is a product of matrix algebras.

Abstract

We study the structure of certain classes of homologically trivial locally C*-algebras. These include algebras with projective irreducible Hermitian A-modules, biprojective algebras, and superbiprojective algebras. We prove that, if A is a locally C*-algebra, then all irreducible Hermitian A-modules are projective if and only if A is a direct topological sum of elementary C*-algebras. This is also equivalent to A being an annihilator (dual, complemented, left quasi-complemented, or topologically modular annihilator) topological algebra. We characterize all annihilator $\sigma$-C*-algebras and describe the structure of biprojective locally C*-algebras. Also, we present an example of a biprojective locally C*-algebra that is not topologically isomorphic to a Cartesian product of biprojective C*-algebras. Finally, we show that every superbiprojective locally C*-algebra is topologically *-isomorphic to a Cartesian product of full matrix algebras.