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We show the singular ideal in a non-Hausdorff \'etale groupoid C*-algebra is zero if and only if every unit is contained, at the level of group representation theory, in the collection of subgroups of the unit's isotropy group obtained as…

Operator Algebras · Mathematics 2025-10-28 Jeremy B. Hume

We give a complete classification of the ideals of the core of the C*-algebras associated with self-similar maps under a certain condition. Any ideal is completely determined by the intersection with the coefficient algebra C(K) of the…

Operator Algebras · Mathematics 2013-06-11 Tsuyoshi Kajiwara , Yasuo Watatani

We characterise, in several complementary ways, \'etale groupoids with locally compact Hausdorff space of units whose essential groupoid C*-algebra has the ideal intersection property, assuming that the groupoid is topologically transitive…

Operator Algebras · Mathematics 2024-09-04 Matthew Kennedy , Se-Jin Kim , Xin Li , Sven Raum , Dan Ursu

Let $B \subseteq A$ be an inclusion of C$^*$-algebras. We study the relationship between the regular ideals of $B$ and regular ideals of $A$. We show that if $B \subseteq A$ is a regular C$^*$-inclusion and there is a faithful invariant…

Operator Algebras · Mathematics 2023-11-30 Jonathan H. Brown , Adam H. Fuller , David R. Pitts , Sarah A. Reznikoff

We prove that if a connected and simply connected Lie group $G$ admits connected closed normal subgroups $G_1\subseteq G_2\subseteq \cdots \subseteq G_m=G$ with $\dim G_j=j$ for $j=1,\dots,m$, then its group $C^*$-algebra has closed…

Operator Algebras · Mathematics 2025-04-15 Ingrid Beltita , Daniel Beltita

We define a notion of Property (T) for an arbitrary $C^*$-algebra $A$ admitting a tracial state. We extend this to a notion of Property (T) for the pair $(A,B),$ where $B$ is a $C^*$-subalgebra of $A.$ Let $\Gamma$ be a discrete group and…

Operator Algebras · Mathematics 2015-02-04 Bachir Bekka

We define a basis property that an inclusion of C*-algebras $\mathcal O_\infty\subset A$ may have, and give various conditions for the property to hold. Some applications are considered. We also give a characterization of open projections…

Operator Algebras · Mathematics 2023-06-28 Dan Kucerovsky

In this paper, we will define the reduced cross-sectional $C^*$-algebras of $C^*$-algebraic bundles over locally compact groups and show that if a $C^*$-algebraic bundle has the approximation property (defined similarly as in the discrete…

Operator Algebras · Mathematics 2007-05-23 Ruy Exel , Chi-Keung Ng

We show that every proper, dense ideal in a C*-algebra is contained in a prime ideal. It follows that a subset generates a C*-algebra as a not necessarily closed ideal if and only if it is not contained in any prime ideal. This allows us to…

Operator Algebras · Mathematics 2023-08-11 Eusebio Gardella , Hannes Thiel

Let $p\in(1,\infty)\backslash\{2\}$. We show that every homomorphism from a $C^{*}$-algebra $\mathcal{A}$ into $B(l^{p}(J))$ satisfies a compactness property where $J$ is any set. As a consequence, we show that a $C^{*}$-algebra…

Functional Analysis · Mathematics 2019-09-13 March T. Boedihardjo

A classification is given of certain separable nuclear C*-algebras not necessarily of real rank zero, namely, the class of separable simple C*-algebras which are inductive limits of continuous-trace C*-algebras whose building blocks have…

Operator Algebras · Mathematics 2007-05-23 George A. Elliott , Cristian Ivanescu

We characterize the lifting property (LP) of a separable $C^*$-algebra $A$ by a property of its maximal tensor product with other $C^*$-algebras, namely we prove that $A$ has the LP if and only if for any family $(\{D_i\mid i\in I\}$ of…

Operator Algebras · Mathematics 2023-04-05 Gilles Pisier

With each Fell bundle over a discrete group G we associate a partial action of G on the spectrum of the unit fiber. We discuss the ideal structure of the corresponding full and reduced cross-sectional C*-algebras in terms of the dynamics of…

Operator Algebras · Mathematics 2015-04-23 Beatriz Abadie , Fernando Abadie

For a locally convex $^*$-algebra $A$ equipped with a fixed continuous $^*$-character $\varepsilon$, we define a cohomological property, called property $(FH)$, which is similar to character amenability. Let $C_c(G)$ be the space of…

Functional Analysis · Mathematics 2015-09-08 Xiao Chen , Anthony To-Ming Lau , Chi-Keung Ng

We investigate the ideal structures of the C^*-algebras arising from topological graphs. We give the complete description of ideals of such C^*-algebras which are invariant under the so-called gauge action, and give the condition on…

Operator Algebras · Mathematics 2007-05-23 Takeshi Katsura

We introduce the notion of relative topological principality for a family $\{H_\alpha\}$ of open subgroupoids of a Hausdorff \'etale groupoid $G$. The C*-algebras $C^*_r(H_\alpha)$ of the groupoids $H_\alpha$ embed in $ C^*_r(G)$ and we…

Operator Algebras · Mathematics 2024-11-06 Chris J. Eagle , Gavin Goerke , Marcelo Laca

We study the topology of the primitive ideal space of groupoid C*-algebras for groupoids with abelian isotropy. Our results include the known results for action groupoids with abelian stabilizers. Furthermore, we obtain complete results…

Operator Algebras · Mathematics 2021-08-26 Daniel W. van Wyk , Dana P. Williams

For every $p\geq 2$, we give a characterization of positive definite functions on a free group with finitely many generators, which can be extended to the positive linear functionals on the free group $C^*$-algebra associated with the ideal…

Operator Algebras · Mathematics 2012-07-13 Rui Okayasu

We introduce a notion of a uniform structure on the set of all representations of a given separable, not necessarilly commutative $C^*$-algebra $\mathfrak{A}$ by introducing a suitable family of metrics on the set of representations of…

Operator Algebras · Mathematics 2018-05-17 Adam Wegert

Inspired by results for graph $C^*$-algebras, we investigate connections between the ideal structure of an inverse semigroup $S$ and that of its tight $C^*$-algebra by relating ideals in $S$ to certain open invariant sets in the associated…

Operator Algebras · Mathematics 2019-01-29 Scott M. LaLonde , David Milan , Jamie Scott