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Convolution semigroups of states on a quantum group form the natural noncommutative analogue of convolution semigroups of probability measures on a locally compact group. Here we initiate a theory of weakly continuous convolution semigroups…

Operator Algebras · Mathematics 2009-10-28 J. Martin Lindsay , Adam Skalski

An amalgam of inverse semigroups [S,T,U] is full if U contains all of the idempotents of S and T. We show that for a full amalgam [S,T,U], the C*-algebra of the inverse semigroup amaglam of S and T over U is the C*-algebraic amalgam of…

Operator Algebras · Mathematics 2010-07-08 Allan P Donsig , Steven P. Haataja , John C. Meakin

We consider representations of the free group $F_2$ on two generators such that the norm of the sum of the generators and their inverses is bounded by $\mu\in[0,4]$. These $\mu$-constrained representations determine a C*-algebra $A_{\mu}$…

Operator Algebras · Mathematics 2015-05-19 Vladimir Manuilov , Chao You

We introduce a $C^*$-algebra $\mathscr{A}_V$ of a variety $V$ over the number field $K$ and a $C^*$-algebra $\mathscr{A}_G$ of a reductive group $G$ over the ring of adeles of $K$. Using Pimsner's Theorem we construct an embedding…

Number Theory · Mathematics 2021-04-07 Igor Nikolaev

We introduce a notion of ellipticity of complexes of linear pseudodifferential operators acting on sections of $A$-Hilbert bundles over smooth manifolds, $A$ being a $C^*$-algebra. We prove that the cohomology groups of an $A$-elliptic…

Operator Algebras · Mathematics 2022-08-23 Svatopluk Krýsl

We determine the structure of the weak*-closed $G$-invariant ideals in the Fourier-Stieltjes algebra $B(G)$ of certain groups $G$ by means of a $K$-theoretical obstruction. The groups to which this applies are groups whose only irreducible…

Operator Algebras · Mathematics 2020-05-06 Timo Siebenand

The recently developed theory of partial actions of discrete groups on $C^*$-algebras is extended. A related concept of actions of inverse semigroups on $C^*$-algebras is defined, including covariant representations and crossed products.…

funct-an · Mathematics 2008-02-03 Nandor Sieben

We prove index formulas for elliptic operators acting between sections of C*-vector bundles on a closed manifold. The formulas involve Karoubi's Chern character from K-theory of a C*-algebra to de Rham homology of smooth subalgebras. We…

K-Theory and Homology · Mathematics 2009-01-03 Charlotte Wahl

We prove a complete analog of the Borsuk Homotopy Extension Theorem for arbitrary semiprojective C*-algebras. We also obtain some other results about semiprojective C*-algebras: a partial lifting theorem with specified quotient, a lifting…

Operator Algebras · Mathematics 2015-05-05 Bruce Blackadar

The relation between representations and positive definite functions is a key concept in harmonic analysis on topological groups. Recently this relation has been studied on topological groupoids. This is the first in a series of papers in…

Operator Algebras · Mathematics 2007-05-23 Massoud Amini , Alireza Medghalchi

We prove a new uniqueness theorem for the tight C*-algebras of an inverse semigroup by generalizing the uniqueness theorem given for \'etale groupoid C*-algebras by Brown, Nagy, Reznikoff, Sims, and Williams. We use this to show that in the…

Operator Algebras · Mathematics 2022-08-18 Charles Starling

Let G be a locally compact Abelian group. Following Ruy Exel, we view Fell bundles over the Pontrjagin dual of G as continuous spectral decompositions of G-actions on C*-algebras. We classify such spectral decompositions using certain dense…

Operator Algebras · Mathematics 2015-10-23 Alcides Buss , Ralf Meyer

Groupoid actions on C*-bundles and inverse semigroup actions on C*-algebras are closely related when the groupoid is r-discrete.

Operator Algebras · Mathematics 2007-05-23 John Quigg , Nandor Sieben

In recent times a new kind of representations has been used to describe superselection sectors of the observable net over a curved spacetime, taking into account of the effects of the fundamental group of the spacetime. Using this notion of…

Mathematical Physics · Physics 2015-05-27 Giuseppe Ruzzi , Ezio Vasselli

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

We study $C^*$-algebras arising from $C^*$-correspondences, which was introduced by the author. We prove the gauge-invariant uniqueness theorem, and obtain conditions for our $C^*$-algebras to be nuclear, exact, or satisfy the Universal…

Operator Algebras · Mathematics 2007-05-23 Takeshi Katsura

We study Blackadar and Kirchberg's matricial field (MF) property and quasidiagonality in cross-sectional C*-algebras constructed from Fell Bundles and, in particular, from partial C*-dynamical systems. In doing so we generalize Kerr and…

Operator Algebras · Mathematics 2023-07-04 Timothy Rainone

We study C*-algebra endomorphims which are special in a weaker sense w.r.t. the notion introduced by Doplicher and Roberts. We assign to such endomorphisms a geometrical invariant, representing a cohomological obstruction for them to be…

Operator Algebras · Mathematics 2011-11-21 Ezio Vasselli

We prove stability theorems in the Cuntz semigroup of a commutative C*-algebra which are analogues of classical stability theorems for topological vector bundles over compact Hausdorff spaces. Several applications to simple unital AH…

Operator Algebras · Mathematics 2014-02-26 Andrew S. Toms

We investigate recent uniqueness theorems for reduced $C^*$-algebras of Hausdorff \'{e}tale groupoids in the context of inverse semigroups. In many cases the distinguished subalgebra is closely related to the structure of the inverse…

Operator Algebras · Mathematics 2016-11-11 Scott M. LaLonde , David Milan