Constructing equivalence bimodules between noncommutative solenoids: a two-pronged approach

TL;DR

This paper generalizes a method for constructing Morita equivalence bimodules between noncommutative solenoid C*-algebras by using direct limits of rotation algebras and fixed projections, establishing criteria for Morita equivalence.

Contribution

It introduces a two-pronged approach to construct equivalence bimodules between noncommutative solenoids, extending previous methods and connecting different bimodule constructions.

Findings

Morita equivalence of irrational noncommutative solenoids characterized by existence of a fixed projection.

Constructed directed systems of bimodules satisfying compatibility conditions.

Connected Heisenberg bimodules with the new construction.

Abstract

We revisit and generalize the application of a method introduced by Latr\'emoli\`ere and Packer for constructing finitely generated projective modules over the noncommutative solenoid C*-algebras. By realizing them as direct limits of rotation algebras, the method constructs directed systems of equivalence bimodules between rotation algebras that satisfy the necessary compatibility conditions to build Morita equivalence bimodules between the direct limit C*-algebras. In the irrational case, we use a fixed projection in a matrix algebra over the rotation algebra satisfying a key condition to build an equivalence bimodule at each stage following a construction of Rieffel. From this, our main result shows that two irrational noncommutative solenoids are Morita equivalent if and only if such a projection exists. We also make additional observations about the Heisenberg bimodules construction studied by the aforementioned two authors and connect the two constructions.