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Consider a proper, isometric action by a unimodular locally compact group $G$ on a Riemannian manifold $M$ with boundary, such that $M/G$ is compact. Then an equivariant Dirac-type operator $D$ on $M$ under a suitable boundary condition has…

K-Theory and Homology · Mathematics 2020-06-16 Peter Hochs , Bai-Ling Wang , Hang Wang

Given a C*-dynamical system (A,G,\alpha), we discuss conditions under which subalgebras of the multiplier algebra M(A) consisting of fixed points for \alpha are Morita-Rieffel equivalent to ideals in the crossed product of A by G. In case G…

Operator Algebras · Mathematics 2007-05-23 Ruy Exel

The set of all maximal ideals of the ring $\mathcal{M}(X,\mathcal{A})$ of real valued measurable functions on a measurable space $(X,\mathcal{A})$ equipped with the hull-kernel topology is shown to be homeomorphic to the set $\hat{X}$ of…

Functional Analysis · Mathematics 2018-06-11 Sudip Kumar Acharyya , Sagarmoy Bag , Joshua Sack

The main aim of this paper is to characterize ideals I in the power series ring R=K[[x1,...,xs]] that are finitely determined up to contact equivalence by proving that this is the case if and only if I is an isolated complete intersection…

Algebraic Geometry · Mathematics 2019-05-09 Gert-Martin Greuel , Thuy Huong Pham

Following Robert's [26], we study the structure of unitary groups and groups of approximately inner automorphisms of unital $C^*$-algebras, taking advantage of the former being Banach-Lie groups. For a given unital $C^*$-algebra $A$, we…

Operator Algebras · Mathematics 2025-01-06 Hiroshi Ando , Michal Doucha

We establish new results on the $\mathcal I$-approximation property for the Banach operator ideal $\mathcal I=\mathcal{K}_{up}$ of the unconditionally $p$-compact operators in the case of $1\le p<2$. As a consequence of our results, we…

Functional Analysis · Mathematics 2023-10-09 Henrik Wirzenius

We survey the results required to pass between full and reduced coactions of locally compact groups on C*-algebras, which say, roughly speaking, that one can always do so without changing the crossed-product C*-algebra. Wherever possible we…

Operator Algebras · Mathematics 2010-01-22 Astrid an Huef , John Quigg , Iain Raeburn , Dana P. Williams

There seems to be quite a bit of room for interesting things related to surfaces M in C^m with real dimension m which are totally real and aspects of several complex variables on C^m around M. A basic case occurs when m = 1, with Cauchy…

Classical Analysis and ODEs · Mathematics 2007-05-23 Stephen Semmes

We develop a new functional-analytic technique for investigating the degree of noncompactness of an operator defined on a quasinormed space and taking values in a Marcinkiewicz space. The main result is a general principle from which it can…

Functional Analysis · Mathematics 2025-11-25 Jan Malý , Zdeněk Mihula , Vít Musil , Luboš Pick

In a lossless compression system with target lengths, a compressor ${\cal C}$ maps an integer $m$ and a binary string $x$ to an $m$-bit code $p$, and if $m$ is sufficiently large, a decompressor ${\cal D}$ reconstructs $x$ from $p$. We call…

Information Theory · Computer Science 2019-11-12 Bruno Bauwens , Marius Zimand

Answering questions raised in \cite{Leonetti, Uzcategui} we characterize ideals $\mathcal I\subseteq \mathcal P(\omega)$ such that $c_{0,\mathcal I}$ is complemented in $\ell_\infty$ as exactly those ideals for which the space $K_{\mathcal…

Functional Analysis · Mathematics 2025-12-02 Michael Hrušák , Luis Sáenz

This article is to give an infinite dimensional analogue of a result of Choi and Effros. We say that an (not necessarily unital) operator system $T$ is \emph{dualizable} if one can find an equivalent dual matrix norm on the dual space $T^*$…

Operator Algebras · Mathematics 2022-02-10 Chi-Keung Ng

A notion of partial ideal for an operator algebra is a weakening the notion of ideal where the defining algebraic conditions are enforced only in the commutative subalgebras. We show that, in a von Neumann algebra, the ultraweakly closed…

Operator Algebras · Mathematics 2014-08-07 Nadish de Silva , Rui Soares Barbosa

In this article, we give an abstract characterization of the ``identity'' of an operator space $V$ by looking at a quantity $n_{cb}(V,u)$ which is defined in analogue to a well-known quantity in Banach space theory. More precisely, we show…

Operator Algebras · Mathematics 2008-05-27 Xu-Jian Huang , Chi-Keung Ng

The operator space analogue of the {\em strong form} of the principle of local reflexivity is shown to hold for any von Neumann algebra predual, and thus for any $C^{*}$-algebraic dual. This is in striking contrast to the situation for…

Operator Algebras · Mathematics 2007-05-23 Edward G. Effros , Marius Junge , Zhong-Jin Ruan

In the set of continuous functions C(X,Y) where Y has a topology close to being discrete, there is an equivalence relation on X which characterizes the quasi-components of X. If Y satisfies weak algebraic conditions with a single binary…

Rings and Algebras · Mathematics 2014-07-14 Harvey J. Charlton

In the setting of adjoint pairs of operators we consider the question: to what extent does the Weyl M-function see the same singularities as the resolvent of a certain restriction $A_B$ of the maximal operator? We obtain results showing…

Spectral Theory · Mathematics 2009-02-09 Malcolm Brown , James Hinchcliffe , Marco Marletta , Serguei Naboko , Ian Wood

Two separated realcompact measurable spaces $(X,\mathcal{A})$ and $(Y,\mathcal{B})$ are shown to be isomorphic if and only if the rings $\mathcal{M}(X,\mathcal{A})$ and $\mathcal{M}(Y,\mathcal{B})$ of all real valued measurable functions…

General Topology · Mathematics 2018-11-07 Soumyadip Acharyya , Sudip Kumar Acharyya , Sagarmoy Bag , Joshua Sack

We give a solution, via operator spaces, of an old problem in the Morita equivalence of C*-algebras. Namely, we show that C*-algebras are strongly Morita equivalent in the sense of Rieffel if and only if their categories of left operator…

Operator Algebras · Mathematics 2007-05-23 David P. Blecher

For a Banach space $X$, let $\mathcal{L}(X)$ denote the algebra of all bounded linear operators on $X$ and let $\mathcal{K}(X)$ denote the compact operator ideal in $\mathcal{L}(X)$. The quotient algebra $\mathcal{L}(X)/\mathcal{K}(X)$ is…

Functional Analysis · Mathematics 2024-03-08 Pavlos Motakis , Daniele Puglisi