Nica-Toeplitz algebras associated with right tensor $C^{\ast }$-precategories over right LCM semigroups

Abstract

We introduce and analyze the full ${\mathcal{N}\mathcal{T}}_{\mathcal{L}}(\mathcal{K})$ and the reduced ${\mathcal{N}\mathcal{T}}_{\mathcal{L}}^r(\mathcal{K})$ Nica-Toeplitz algebra associated to an ideal $\mathcal{K}$ in a right tensor $C^{\ast }$-precategory $\mathcal{L}$ over a right LCM semigroup $P$. Our main results are uniqueness theorems in the spirit of classical Coburn's theorem, generalizing uniqueness results for Toeplitz-type $C^{\ast }$-algebras associated to single $C^{\ast }$-correspondences, quasi-lattice ordered semigroups, and crossed products twisted by product systems of $C^{\ast }$-correspondences obtained by Fowler, Laca and Raeburn. We formulate geometric conditions on a representation $\Phi$ of $\mathcal{K}$ so that the $C^{\ast }$-algebra it generates, $C^{\ast }(\Phi (\mathcal{K}))$, naturally lies between ${\mathcal{N}\mathcal{T}}_{\mathcal{L}}^r(\mathcal{K})$ and ${\mathcal{N}\mathcal{T}}_{\mathcal{L}}(\mathcal{K})$. Under suitable amenability hypotheses, $C^{\ast }(\Phi (\mathcal{K}))$ and ${\mathcal{N}\mathcal{T}}_{\mathcal{L}}(\mathcal{K})$ are isomorphic. The geometric conditions are necessary for our uniqueness result when the right tensoring preserves $\mathcal{K}$ and in general they capture uniqueness of the $C^{\ast }$-algebra generated by a natural extension of $\Phi$ to $\mathcal{L}$. In particular, the latter algebra could be viewed as a Doplicher-Roberts version of ${\mathcal{N}\mathcal{T}}_{\mathcal{L}}(\mathcal{K})$.

arXiv commentTitle shortened, introduction and abstract rewritten. Reference [20] to the article with applications added