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The theory of one-sided $M$-ideals and multipliers of operator spaces is simultaneously a generalization of classical $M$-ideals, ideals in operator algebras, and aspects of the theory of Hilbert $C^*$-modules and their maps. Here we give a…

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

The difficulty for solving ill-posed linear operator equations in Hilbert space is reflected by the strength of ill-posedness of the governing operator, and the inherent solution smoothness. In this study we focus on the ill-posedness of…

Numerical Analysis · Mathematics 2025-01-24 Peter Mathé , Bernd Hofmann

General, especially spectral, features of compact normal operators in quaternionic Hilbert spaces are studied and some results are established which generalize well-known properties of compact normal operators in complex Hilbert spaces.…

Functional Analysis · Mathematics 2014-02-14 Riccardo Ghiloni , Valter Moretti , Alessandro Perotti

This short but self-contained survey presents a number of elegant matrix/operator inequalities for general convex or concave functions, obtained with a unitary orbit technique. Jensen, sub or super-additivity type inequalities are…

Functional Analysis · Mathematics 2014-02-26 Jean-Christophe Bourin , Eun-Young Lee

The Operator axioms have produced new real numbers with new operators. New operators naturally produce new equations and thus extend the traditional mathematical models which are selected to describe various scientific rules. So new…

Numerical Analysis · Computer Science 2021-02-08 Pith Peishu Xie

In this article, we present some new inequalities for the numerical radius of products of Hilbert space operators and the generalized Aluthge transform. In particular, we show some upper bounds for $\omega(ABC+DEF)$ using the celebrated…

Functional Analysis · Mathematics 2022-06-03 Mohammad Sababheh , Cristian Conde , Hamid Reza Moradi

We present a treasure trove of open problems in matrix and operator inequalities, of a functional analytic nature, and with various degrees of hardness.

Functional Analysis · Mathematics 2012-05-02 K. M. R. Audenaert , F. Kittaneh

Let $H$ be a reflexive, dense, separable, infinite dimensional complex Hilbert space and let $B(H)$ be the algebra of all bounded linear operators on $H$. In this paper, we carry out characterizations of norm-attainable operators in normed…

Functional Analysis · Mathematics 2020-04-14 Benard Okelo

Let $\mathbb{A}=\left( \begin{array}{cc} A & 0 \\ 0 & A \\ \end{array} \right)$ be the $2\times2$ diagonal operator matrix determined by a positive bounded operator $A$. For semi-Hilbertian operators $X$ and $Y$, we first show that…

Functional Analysis · Mathematics 2020-05-12 Qingxiang Xu , Zhongming Ye , Ali Zamani

The paper introduces unbounded antilinear operators on Hilbert spaces and develops their fundamental theory. In particular, we establish a closed range theorem, a polar decomposition theorem, and the convexity of the numerical range for…

Functional Analysis · Mathematics 2026-05-25 Arup Majumdar

In this paper we introduce a new technique for proving norm inequalities in operator ideals with an unitarily invariant norm. Among the well known inequalities which can be proved with this technique are the L\"owner-Heinz inequality,…

Operator Algebras · Mathematics 2008-08-19 Gabriel Larotonda

We survey several significant results on the Bohr inequality and presented its generalizations in some new approaches. These are some Bohr type inequalities of Hilbert space operators related to the matrix order and the Jensen inequality.…

Functional Analysis · Mathematics 2011-07-08 Masatoshi Fujii , Mohammad Sal Moslehian , Jadranka Micic

In this letter we show that the field of Operator Space Theory provides a general and powerful mathematical framework for arbitrary Bell inequalities, in particular regarding the scaling of their violation within quantum mechanics. We…

Quantum Physics · Physics 2014-11-20 M. Junge , C. Palazuelos , D. Perez-Garcia , I. Villanueva , M. M. Wolf

Functional analysis, especially the theory of Hilbert spaces and of operators on these, form an important area in mathematics. We formalized the Isabelle/HOL library Complex_Bounded_Operators containing a large amount of theorems about…

Logic in Computer Science · Computer Science 2025-12-08 Dominique Unruh , José Manuel Rodríguez Caballero

The main aim of this book is to present recent results concerning inequalities for continuous functions of selfadjoint operators on complex Hilbert spaces. It is intended for use by both researchers in various fields of Linear Operator…

Functional Analysis · Mathematics 2012-03-09 Silvestru Sever Dragomir

Generalizing Pisier's idea, we introduce a Hilbertian matrix cross normed space associated with a pair of symmetric normed ideals. When the two ideals coincide, we show that our construction gives an operator space if and only if the ideal…

Operator Algebras · Mathematics 2007-05-23 Takahiro Ohta

This paper explores the concept of approximate Birkhoff-James orthogonality in the context of operators on semi-Hilbert spaces. These spaces are generated by positive semi-definite sesquilinear forms. We delve into the fundamental…

Functional Analysis · Mathematics 2023-12-19 Cristian Conde , Kais Feki

This paper explores refinements of some operator norm inequalities through the generalized spherical Aluthge transform and the spherical Heinz transform. We introduce the spherical Schatten $p$-norm for operator tuples and establish several…

Functional Analysis · Mathematics 2025-04-01 Fuad Kittaneh , Satyajit Sahoo , Hranislav Stanković

We estimate the operator norm of radial non-negative functions on hyperbolic groups. As a consequence, we show that several forms of Haagerup's inequality are optimal.

Group Theory · Mathematics 2023-11-17 Bogdan Nica

By the use of the celebrated Kato's inequality we obtain in this paper some new inequalities for trace class operators on a complex Hilbert space H. Natural applications for functions defined by power series of normal operators are given as…

Functional Analysis · Mathematics 2014-09-29 Silvestru Sever Dragomir
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