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In this paper, we give the Alzer inequality for Hilbert space operators as follows: Let $A, B$ be two selfadjoint operators on a Hilbert space $\mathcal H$ such that $0 < A, B \le \frac{1}{2}I$, where $I$ is identity operator on $\mathcal…

Functional Analysis · Mathematics 2018-06-29 Ali Morassaei , Farzollah Mirzapour

This paper deals with some simple results about spherical functions of type $\delta$, namely new integral formulas, new results about behavior at infinity and some facts about the related $C_\sigma$ functions.

Representation Theory · Mathematics 2017-09-12 Sigurdur Helgason

We study the manner in which a sequence of spectral shift functions $\xi(\cdot;H_j,H_{0,j})$ associated with abstract pairs of self-adjoint operators $(H_j, H_{0,j})$ in Hilbert spaces $\cH_j$, $j\in\bbN$, converge to a limiting spectral…

Spectral Theory · Mathematics 2011-11-02 Fritz Gesztesy , Roger Nichols

This paper introduces and investigates the concept of the $q$-numerical range for tuples of bounded linear operators in Hilbert spaces. We establish various inequalities concerning the $q$-numerical radius associated with these operator…

Functional Analysis · Mathematics 2024-10-08 Kais Feki , Arnab Patra , Jyoti Rani , Zakaria Taki

A new approach to normal operators in real Hilbert spaces is discussed, and a spectral representation is obtained, derived directly from the complex case. The results are then applied to quaternionic normal operators, regarded as a special…

Functional Analysis · Mathematics 2025-07-28 Florian-Horia Vasilescu

We give new inequalities for $A$-operator seminorm and $A$-numerical radius of semi-Hilbertian space operators and show that the inequalities obtained here generalize and improve on the existing ones. Considering a complex Hilbert space…

Functional Analysis · Mathematics 2024-08-14 Pintu Bhunia , Kallol Paul , Raj Kumar Nayak

In this paper, we derive a generalized multiplicative Hardy-Littlewood-Polya type inequality, as well as several related additive inequalities, for functions of operators in Hilbert spaces. In addition, we find the modulus of continuity of…

Functional Analysis · Mathematics 2015-10-06 Vladyslav Babenko , Yuliya Babenko , Nadiia Kriachko

In this paper we find fractional Riemann-Liouville derivatives for the Takagi-Landsberg functions. Moreover, we introduce their generalizations called weighted Takagi-Landsberg functions which have arbitrary bounded coefficients in the…

Classical Analysis and ODEs · Mathematics 2020-03-31 Vitalii Makogin , Yuliya Mishura

Let $A$ be a positive bounded linear operator acting on a complex Hilbert space $\big(\mathcal{H}, \langle \cdot\mid \cdot\rangle \big)$. Let $\omega_A(T)$ and ${\|T\|}_A$ denote the $A$-numerical radius and the $A$-operator seminorm of an…

Functional Analysis · Mathematics 2020-04-20 Kais Feki

We consider a general schema involving measure spaces, contractions and linear and continuous operators. Within the framework of this schema we use our sesquilinear uniform integral and introduce some integral operators on continuous vector…

Classical Analysis and ODEs · Mathematics 2017-06-16 Ion Chiţescu , Loredana Ioana , Radu Miculescu , Lucian Niţă

The purpose of the article is to generalize the concept of approximate Birkhoff-James orthogonality, in the semi-Hilbertian structure. Given a positive operator $ A $ on a Hilbert space $ \mathbb{H}, $ we define $ (\epsilon,A)- $approximate…

Functional Analysis · Mathematics 2024-08-14 Jeet Sen , Debmalya Sain , Kallol Paul

In this paper we introduce the concept of quadratic operator perspective for a continuous function {\Phi} defined on the positive semi-axis of real numbers. This generalize the quadratic weighted operator geometric mean and the quadratic…

Functional Analysis · Mathematics 2016-09-29 Silvestru Sever Dragomir

We discuss the evaluation of certain d dimensional angular integrals which arise in perturbative field theory calculations. We find that the angular integral with n denominators can be computed in terms of a certain special function, the…

High Energy Physics - Phenomenology · Physics 2015-05-27 Gabor Somogyi

In this article, we develop a framework for the joint functional calculus of commuting pair of $\text{Ritt}_{\text{E}}$ operators on Banach spaces. We establish a transfer principle that relates the bounded holomorphic functional calculus…

Functional Analysis · Mathematics 2026-04-22 Suman Mondal , Subhajit Palai , Samya Kumar Ray

In this article we consider the generalized integral operators acting on the Hilbert space $H^2$. We characterize when these operators are uniform, strong and weakly asymptotic Toeplitz and Hankel operators. Moreover we completely describe…

Functional Analysis · Mathematics 2024-09-17 C. Bellavita , G. Stylogiannis

We apply the inequality $\left|\left<x,y\right>\right|\le\|x\|\,\left<y,y\right>^{1/2}$ to give an easy and elementary proof of many operator inequalities for elementary operators and inner type product integral transformers obtained during…

Functional Analysis · Mathematics 2018-01-25 Dragoljub J. Kečkić

The existence of kinematic formulas for area measures with respect to any connected, closed subgroup of the orthogonal group acting transitively on the unit sphere is established. In particular, the kinematic operator for area measures is…

Differential Geometry · Mathematics 2013-08-29 Thomas Wannerer

This paper presents the fractional trigonometric functions in complex-valued space and proposes a short outline of local fractional calculus of complex function in fractal spaces.

Mathematical Physics · Physics 2011-10-31 Xiao-Jun Yang

In this work, some generalizations and refinements inequalities for numerical radius of the product of Hilbert space operators are proved. New inequalities for numerical radius of block matrices of Hilbert space operators are also…

Functional Analysis · Mathematics 2019-03-18 Mohammad W. Alomari

In the paper we prove several inequalities involving two isotonic linear functionals. We consider inequalities for functions with variable bounds, for Lipschitz and H\" older type functions etc. These results give us an elegant method for…

Functional Analysis · Mathematics 2016-12-02 Mea Bombardelli , Ludmila Nikolova , Sanja Varošanec
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