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In this paper, subnormal operators, not necessarily bounded, are discussed as generalized observables. In order to describe not only the information about the probability distribution of the output data of their measurement but also a…

Quantum Physics · Physics 2009-11-06 Masahito Hayashi , Fuminori Sakaguchi

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

In this paper, we study weighted composition operators on the Fock space. We show that a weighted composition operator is cohyponorma if and only if it is normal. Moreover, we give a complete characterization of closed range weighted…

Functional Analysis · Mathematics 2018-09-14 Mahsa Fatehi

We reconsider studies of Toeplitz operators on function spaces (the weighted Bergman space, the generalized derivative Hardy space) and the H-Toeplitz operators on the Bergman space. Past studies have considered the presence or absence of…

Functional Analysis · Mathematics 2024-09-20 Chafiq Benhida , George R. Exner , Ji Eun Lee , Jongrak Lee

We study weighted composition operators on Hilbert spaces of analytic functions on the unit ball with kernels of the form $(1-<z,w>)^{-\gamma}$ for $\gamma>0$. We find necessary and sufficient conditions for the adjoint of a weighted…

Functional Analysis · Mathematics 2012-07-26 Trieu Le

In this paper, by introducing some parameters, we define and study certain $p$-adic Hardy-Littlewood-P\'{o}lya-type integral operators acting on $p$-adic weighted Lebesgue spaces. We completely characterize $L^{q}-L^{r}$ boundedness of…

Functional Analysis · Mathematics 2025-11-21 Jianjun Jin , Huabing Li

The concepts of weighted numerical radius has been defined in recent times. In this article, we obtain several upper bound for weighted numerical radius of operators and $2 \times 2$ operator matrices which generalize and improves some well…

Functional Analysis · Mathematics 2023-02-24 Raj Kumar Nayak

In this paper we attempt to lay the foundations for a theory encompassing some natural extensions of the class of subnormal operators, namely the $n$--subnormal operators and the sub-$n$--normal operators. We discuss inclusion relations…

Functional Analysis · Mathematics 2026-05-12 Raúl E. Curto , Thankarajan Prasad

This paper constructs weight-shifting integral operators for Maass forms on the full modular group SL(2,Z). Under the weight parity condition t = k (mod 2), the operator utilizes an automorphic kernel constructed via Poincare series from a…

Number Theory · Mathematics 2025-12-01 Seung Ju Lee

In this article, we characterize absolutely norm attaining normal operators in terms of the essential spectrum. Later we prove a structure theorem for hyponormal absolutely norm attaining (or $\mathcal{AN}$-operators in short) and deduce…

Functional Analysis · Mathematics 2020-12-14 Neeru Bala , Ramesh G

A weighted mean matrix whose weight sequence is linear with positive coefficients is shown to be a posinormal operator on $\ell^2$. This operator is also shown to be coposinormal, so it and its adjoint have the same null space and the same…

Functional Analysis · Mathematics 2019-01-18 H. C. Rhaly

In this paper, we present a sufficient condition on a pair of nonnegative weights $v$ and $w$ such that we have a general weighted $L^{p}$-Hardy type identity. The result, for a certain choice of weights, gives weighted $L^{p}$-Hardy type…

Functional Analysis · Mathematics 2025-10-03 Nurgissa Yessirkegenov , Amir Zhangirbayev

In this paper we study the commutators of fractional type integral operators. This operators are given by kernels of theform $$K(x,y)=k_1(x-A_1y)k_2(x-A_2y)\dots k_m(x-A_my),$$ where $A_i$ are invertibles matrices and each $k_i$ satisfies a…

Classical Analysis and ODEs · Mathematics 2018-04-27 Gonzalo H. Ibañez-Firnkorn , María Silvina Riveros

A closed densely defined operator $ T $ on a Hilbert space $ \mathcal{H} $ is callled $M$-hyponormal if $\mathcal{D}(T) \subset \mathcal{D}(T^{*}) $ and there exists $ M > 0 $ for which $ \parallel(T-zI)^{*}x \parallel \leq M…

Functional Analysis · Mathematics 2022-06-29 T. Prasad , E. Shine Lal , P. Ramya

Let $H_1$, $H_2$ be complex Hilbert spaces. A bounded linear operator $T : H_1 \to H_2$ is said to be norm attaining if there exists a unit vector $x \in H_1$ such that $\|Tx\| = \|T\|$. If $T|_{M} : M \to H_2$ is norm attaining for every…

Functional Analysis · Mathematics 2022-08-16 G. Ramesh , Shanola S. Sequeira

In this paper we characterize quasi-contraction, stable and convergent weighted conditional type (WCT) operators on $L^p(\mu)$. Indeed we provide equivalent conditions for quasi-contraction WCT operators. Also, we prove that convergence,…

Functional Analysis · Mathematics 2024-06-13 Y. Estaremi , Z. Huang

Bounded and compact generalized weighted composition operators acting from the weighted Bergman space $A^p_\omega$, where $0<p<\infty$ and $\omega$ belongs to the class $\mathcal{D}$ of radial weights satisfying a two-sided doubling…

Complex Variables · Mathematics 2020-08-26 Bin Liu

The main theme of this paper is to give sufficient conditions for the weighted boundedness of the bilinear fractional integral operator $\mathsf{BI}_\al$. The proposed condition involves the union of multilinear Muckenhoupt-type conditions.…

Functional Analysis · Mathematics 2025-07-22 Cong Hoang

We establish a weighted inequality for fractional maximal and convolution type operators, between weak Lebesgue spaces and Wiener amalgam type spaces on $ \mathbb R $ endowed with a measure which needs not to be doubling.

Classical Analysis and ODEs · Mathematics 2018-10-05 Aïssata Adama , Justin Feuto , Ibrahim Fofana

An absolute continuity approach to quasinormality which relates the operator in question to the spectral measure of its modulus is developed. Algebraic characterizations of some classes of operators that emerged in this context are…

Functional Analysis · Mathematics 2013-10-15 Zenon Jan Jablonski , Il Bong Jung , Jan Stochel