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In this article we study different aspects of Hermitian operators applying the concept of positive decompositions. On the one hand, we characterize the positivity of an Hermitian operator by means of a norm condition where the factors of…

Functional Analysis · Mathematics 2024-12-31 Guillermina Fongi , María Celeste Gonzalez

We provide a characterisations of nuclear weighted conditional expectation operators on $L^p(\mu)$-spaces, for $1\leq p<\infty$. As a consequence, when the underlying measure space is non-atomic, the only nuclear weighted conditional…

Functional Analysis · Mathematics 2026-02-24 M. S. Al Ghafri , S. Shamsigamchi , Y. Estaremi

This paper introduces and investigates the class of \textit{$k$-quasi $n$-power posinormal operators} in Hilbert spaces, generalizing both posinormal and $n$-power posinormal operators. We establish fundamental properties including matrix…

Functional Analysis · Mathematics 2025-09-18 Sophiya S Dharan , T. Prasad , M. H. M. Rashid

The general decomposition theory of exponential operators is briefly reviewed. A general scheme to construct independent determining equations for the relevant decomposition parameters is proposed using Lyndon words. Explicit formulas of…

Mathematical Physics · Physics 2009-12-04 Zengo Tsuboi , Masuo Suzuki

The separate tasks of denoising, least squares expectation, and manifold learning can often be posed in a common setting of finding the conditional expectations arising from a product of two random variables. This paper focuses on this more…

Machine Learning · Statistics 2024-02-15 Suddhasattwa Das

Let $L$ be a non-negative self-adjoint operator on $L^2(\mathbb{R}^n)$. By spectral theory, we can define the operator $F(L)$, which is bounded on $L^2(X)$, for any bounded Borel function $F$. In this paper, we study the sharp weighted…

Classical Analysis and ODEs · Mathematics 2012-03-19 The Anh Bui

In this paper, a new characterization is provided for the boundedness, compactness and essential norm of the difference of two weighted composition operators on weighted-type spaces in the unit ball of $\mathbb{C}^n$.

Complex Variables · Mathematics 2018-04-12 Bingyang Hu , Songxiao Li

In this paper we investigate the $L^p$-boundedness of certain classes of periodic pseudo-differential operators. The operators considered arise from the study of symbols on $\mathbb{T}^n\times\mathbb{Z}^n$ with limited regularity.

Analysis of PDEs · Mathematics 2017-01-31 Duván Cardona

Various formulas for reciprocals of densely defined weighted composition operators in $L^2$-spaces as well as for their adjoints are provided. The relation between the reciprocal of a weighted composition operator and the product of the…

Functional Analysis · Mathematics 2024-11-27 Piotr Budzyński

In this paper, we investigate the spectral radius al- gebras related to the weighted conditional expectation operators on the Hilbert spaces L2(F). We give a large classes of operators on L2(F) that have the same spectral radius algebra. As…

Functional Analysis · Mathematics 2016-02-15 Yousef Estaremi , Mohammad Reza Jabbarzadeh

In the setting of adjointable operators on Hilbert $C^*$-modules, this paper deals with the polar decomposition of the product of three operators. The relationship between the polar decompositions associated with three operators is…

Functional Analysis · Mathematics 2024-02-22 Dingyi Du , Qingxiang Xu , Shuo Zhao

We consider an integral operator $\mathcal{I}$, special instances of which was studied in various contexts. Using an appropriate transformation we write this operator in terms of weighted composition operators. Then, we provide a…

Complex Variables · Mathematics 2012-04-16 Epaminondas Diamantopoulos

We provide a detailed description of the model Hilbert space $L^2(\bbR; d\Sigma; \cK)$, were $\cK$ represents a complex, separable Hilbert space, and $\Sigma$ denotes a bounded operator-valued measure. In particular, we show that several…

Spectral Theory · Mathematics 2011-11-04 Fritz Gesztesy , Rudi Weikard , Maxim Zinchenko

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 study power boundedness and related properties such as mean ergodicity for (weighted) composition operators on function spaces defined by local properties. As a main application of our general approach we characterize when (weighted)…

Functional Analysis · Mathematics 2019-03-27 Thomas Kalmes

In this paper, we investigate the spectra of invertible weighted composition operators with automorphism symbols, on Hardy space $H^2(\mathbb{B}_N)$ and weighted Bergman spaces $A_\alpha^2(\mathbb{B}_N)$, where $\mathbb{B}_N$ is the unit…

Functional Analysis · Mathematics 2014-06-19 Yong-Xin Gao , Ze-Hua Zhou

We study the properties of power-boundedness, Li-Yorke chaos, distributional chaos, absolutely Ces\`aro boundedness and mean Li-Yorke chaos for weighted composition operators on $L^p(\mu)$ spaces and on $C_0(\Omega)$ spaces. We illustrate…

Dynamical Systems · Mathematics 2025-12-09 Nilson C. Bernardes , Antonio Bonilla , João V. A. Pinto

In this paper, by using the decomposition theorem for weak Hardy spaces, we will obtain the boundedness properties of some integral operators with variable kernels on these spaces, under some Dini type conditions imposed on the variable…

Classical Analysis and ODEs · Mathematics 2014-01-27 Hua Wang

Unbounded composition operators in $L^2$-space over discrete measure spaces are investigated. Normal, formally normal and quasinormal composition operators acting in $L^2$-spaces of this kind are characterized.

Functional Analysis · Mathematics 2014-08-15 Piotr Budzynski

We provide a characterisations of nuclear weighted conditional expectation operators between different $L^p(\mu)$-spaces. As a consequence, when the underlying measure space is non-atomic, the only nuclear weighted conditional expectation…

Functional Analysis · Mathematics 2026-03-24 A. Ommi , Y. Estaremi