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In this paper we survey our recent work on C*-correspondences and their associated operator algebras; in particular, on adding tails, the Shift Equivalence Problem and Hilbert bimodules.

Operator Algebras · Mathematics 2014-04-08 Evgenios T. A. Kakariadis , Elias G. Katsoulis

The primary purpose of the present paper is to investigate when relations of the types $|AB|=|A||B|$, $|A\pm B|\leq |A|+|B|$, $||A|-|B||\leq |A\pm B|$ and $|\overline{\text{Re} A}|\leq |A|$ (among others) hold in an unbounded operator…

Functional Analysis · Mathematics 2018-05-01 Imene Boucif , Souheyb Dehimi , Mohammed Hichem Mortad

We consider minimal non-negative Jacobi operator with $p\times p-$matrix entries. Using the technique of boundary triplets and the corresponding Weyl functions, we describe the Friedrichs and Krein extensions of the minimal Jacobi operator.…

Spectral Theory · Mathematics 2017-01-24 Aleksandra Ananieva , Nataly Goloshchapova

Let $A$ be a unital operator algebra. Let us assume that every {\it bounded\/} unital homomorphism $u\colon \ A\to B(H)$ is similar to a {\it contractive\/} one. Let $\text{\rm Sim}(u) = \inf\{\|S\|\, \|S^{-1}\|\}$ where the infimum runs…

Functional Analysis · Mathematics 2016-09-07 Gilles Pisier

This is a survey of a variety of equivariant (co)homology theories for operator algebras. We briefly discuss a background on equivariant theories, such as equivariant $K$-theory and equivariant cyclic homology. As the main focus, we discuss…

Operator Algebras · Mathematics 2019-02-12 Massoud Amini , Ahmad Shirinkalam

We present some generalized Jensen type operator inequalities involving sequences of self-adjoint operators. Among other things, we prove that if $f:[0,\infty) \to \mathbb{R}$ is a continuous convex function with $f(0)\leq 0$, then…

Functional Analysis · Mathematics 2014-11-04 M. S. Moslehian , J. Micic , M. Kian

In a previous paper we showed how the main theorems characterizing operator algebras and operator modules, fit neatly into the framework of the `noncommutative Shilov boundary', and more particularly via the left multiplier operator algebra…

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

In the present work we characterized full operators and we showed some properties that have nonfull injectives operators. With the results developed for full operators, we affirmatively respond two questions formulated by Bravo and Feintuch…

Functional Analysis · Mathematics 2009-10-22 Wilson R. Pacheco R

We extend the usual theory of universal C*-algebras from generators and relations in order to allow some relations to be described using the strong operator topology. In particular, we can allow some infinite sum relations. We prove a…

Operator Algebras · Mathematics 2020-08-13 Giuliano Boava , Gilles G. de Castro

In this paper, we establish some basic properties of certain operators (element of centroids, averaging operators, derivations, Nijenhuis operators, Rota-Baxter operators) on (compatible) ternary Leibniz algebras and give the classification…

Rings and Algebras · Mathematics 2025-03-31 Kol Béatrice Gamou , Ahmed Zahari Abdou , Ibrahima Bakayoko

For a closed densely defined operator $T$ from a Hilbert space $\mathfrak{H}$ to a Hilbert space $\mathfrak{K}$, necessary and sufficient conditions are established for the factorization of $T$ with a bounded nonnegative operator $X$ on…

Functional Analysis · Mathematics 2025-07-21 Yosra Barkaoui , Seppo Hassi

Let $\A$ be a $C^*-$algebra with unit element $1$ and unitary group $U.$ Let $a=(a_1, ..., a_k)$ and $b=(b_1, ..., b_k)$ two $k-$tuples of elements in $\A.$ The elementary operator associated to $a$ and $b$ is defined by $ R_{a, b} (x)=…

Operator Algebras · Mathematics 2015-04-20 Mohamed Barraa

Let A be a unital simple separable C*-algebra with strict comparison of positive elements. We prove that the Cuntz semigroup of A is recovered functorially from the Murray-von Neumann semigroup and the tracial state space T(A) whenever the…

Operator Algebras · Mathematics 2009-12-04 Marius Dadarlat , Andrew S. Toms

In this paper, we show refined Young inequalities for two positive operators. Our results refine the ordering relations among the arithmetic mean, the geometric mean and the harmonic mean for two positive operators. In addition, we give two…

Functional Analysis · Mathematics 2011-04-26 Shigeru Furuichi

Using the operator valued Fourier transform, the C*-algebras of connected real two-step nilpotent Lie groups are characterized as algebras of operator fields defined over their spectra. In particular, it is shown by explicit computations,…

Representation Theory · Mathematics 2014-09-22 Janne-Kathrin Günther , Jean Ludwig

We prove that all finite joint distributions of creation and annihilation operators in Monotone and anti-Monotone Fock spaces can be realized as Quantum Central Limit of certain operators on a $C^*$-algebra, at least when the test functions…

Probability · Mathematics 2017-01-02 Vitonofrio Crismale , Francesco Fidaleo , Yun Gang Lu

In this paper we introduce and prove some properties of $(\alpha;\beta)$-normal operators according to semi-Hilbertian space structures. Furthermore we s,ate various inequalities between the A-operator norm and A-numerical radius of…

Functional Analysis · Mathematics 2016-10-12 Abdelkader Benali , Ould Ahmed Mahmoud Sid Ahmed

We prove that operators satisfying the hypotheses of the extrapolation theorem for Muckenhoupt weights are bounded on weighted Morrey spaces. As a consequence, we obtain at once a number of results that have been proved individually for…

Functional Analysis · Mathematics 2017-10-23 Javier Duoandikoetxea , Marcel Rosenthal

It is well known that "bad" quotient spaces (typically: non-Hausdorff) can be studied by associating to them the groupoid C*-algebra of an equivalence relation, that in the "nice" cases is Morita equivalent to the C*-algebra of continuous…

Operator Algebras · Mathematics 2022-07-13 Francesco D'Andrea , Giovanni Landi , Fedele Lizzi

Families of operator identities appeared as a consequence of an existence of finite-dimensional representation of (super) Lie algebras of first-order differential operators and $q$-deformed (quantum) algebras of first-order…

High Energy Physics - Theory · Physics 2009-10-22 Alexander Turbiner , Gerhard Post