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We establish a framework for weak and strong convergence of matrix models to operator-valued semicircular systems parametrized by operator-valued covariance matrices $\eta = (\eta_{i,j})_{i,j \in I}$. Non-commutative polynomials are…

Operator Algebras · Mathematics 2025-09-30 David Jekel , Yoonkyeong Lee , Brent Nelson , Jennifer Pi

We provide sufficient and necessary conditions guaranteeing equations $(A+B)^*=A^*+B^*$ and $(AB)^*=B^*A^*$ concerning densely defined unbounded operators $A,B$ between Hilbert spaces. We also improve the perturbation theory of selfadjoint…

Functional Analysis · Mathematics 2015-07-31 Zoltán Sebestyén , Zsigmond Tarcsay

We establish a weighted version of the $H^p$-theory of quasiconformal mappings.

Complex Variables · Mathematics 2019-04-02 Sita Benedict , Pekka Koskela , Xining Li

We present a streamlined approach for generalized strong and norm convergence of self-adjoint operators in different Hilbert spaces. In particular, we establish convergence of associated (semi-)groups, (essential) spectra and spectral…

Spectral Theory · Mathematics 2026-01-16 Gerald Teschl , Yifei Wang , Bing Xie , Zhe Zhou

We study Krasnoselskii-Mann style iterative algorithms for approximating fixpoints of asymptotically weakly contractive mappings, with a focus on providing generalised convergence proofs along with explicit rates of convergence. More…

Functional Analysis · Mathematics 2021-04-30 Thomas Powell , Franziskus Wiesnet

Using a Hilbert space framework inspired by the methods of orthogonal projections and Hodge decompositions, we study a general class of problems (called Z-problems) that arise in effective media theory, especially within the theory of…

Mathematical Physics · Physics 2023-07-19 Kenneth Beard , Anthony Stefan , Robert Viator , Aaron Welters

In this paper, we presented a new type of metric space called $(\alpha,\beta)$-metric space along with some novel contraction mappings named $(\alpha,\beta)$-contraction and weak $(\alpha,\beta)$-contraction mapping. We established some…

Functional Analysis · Mathematics 2025-06-24 Irfan Ahmed , Shallu Sharma , Sahil Billawria

We show that (for the weak operator topology) the set of unitary operators on a separable infinite-dimensional Hilbert space is residual in the set of all contractions. The analogous result holds for isometries and the strong operator…

Functional Analysis · Mathematics 2014-12-02 Tanja Eisner

The design of fixed point algorithms is at the heart of monotone operator theory, convex analysis, and of many modern optimization problems arising in machine learning and control. This tutorial reviews recent advances in understanding the…

Optimization and Control · Mathematics 2022-07-19 Francesco Bullo , Pedro Cisneros-Velarde , Alexander Davydov , Saber Jafarpour

We prove that for every semigroup of Schwarz maps on the von~Neumann algebra of all bounded linear operators on a Hilbert space which has a subinvariant faithful normal state there exists an associated semigroup of contractions on the space…

Mathematical Physics · Physics 2023-03-02 George Androulakis , Alexander Wiedemann , Matthew Ziemke

A family of random matrices is said to converge strongly to a limiting family of operators if the operator norm of every noncommutative polynomial of the matrices converges to that of the limiting operators. Recent developments surrounding…

Probability · Mathematics 2025-10-15 Ramon van Handel

The aim of this paper is to establish strong convergence theorems for a strongly relatively nonexpansive sequence in a smooth and uniformly convex Banach space. Then we employ our results to approximate solutions of the zero point problem…

Functional Analysis · Mathematics 2020-12-29 Koji Aoyama , Yasunori Kimura , Fumiaki Kohsaka

We study the convergence analysis of a Picard-S iteration method for a particular class of weak-contraction mappings. Furthermore, we prove a data dependence result for fixed point of the class of weak-contraction mappings with the help of…

Functional Analysis · Mathematics 2014-04-02 Faik Gürsoy

The purpose of this paper is to characterize weak supercyclicity for Hilbert-space contractions, which is shown to be equivalent to characterizing weak supercyclicity for unitary operators$.$ This is naturally motivated by an open question…

Functional Analysis · Mathematics 2020-10-27 C. S. Kubrusly , P. C. M. Vieira

We investigate if an existing notion of weak sequential convergence in a Hadamard space can be induced by a topology. We provide an answer on what we call weakly proper Hadamard spaces. A notion of dual space is proposed and it is shown…

Functional Analysis · Mathematics 2025-03-11 Arian Bërdëllima

We characterize the semigroups of composition operators that are strongly continuous on the mixed norm spaces $H(p,q,\alpha)$. First, we study the separable spaces $H(p,q,\alpha)$ with $q<\infty,$ that behave as the Hardy and Bergman…

Functional Analysis · Mathematics 2016-10-28 Irina Arévalo , Manuel D. Contreras , Luis Rodríguez-Piazza

Given a densely defined and closed operator $A$ acting on a complex Hilbert space $\mathcal{H}$, we establish a one-to-one correspondence between its closed extensions and subspaces $\mathfrak{M}\subset\mathcal{D}(A^*)$, that are closed…

Functional Analysis · Mathematics 2018-10-12 Christoph Fischbacher

In 2008, J. Parcet showed the $(1,1)$ weak-boundedness of Calder\'on-Zygmund operators acting on functions taking values in a von Neumann algebra. We propose a simplified version of his proof using the same tools : Cuculescu's projections…

Operator Algebras · Mathematics 2017-11-20 Léonard Cadilhac

We study the typical behavior of bounded linear operators on infinite dimensional complex separable Hilbert spaces in the norm, strong-star, strong, weak polynomial and weak topologies. In particular, we investigate typical spectral…

Functional Analysis · Mathematics 2014-05-01 Tanja Eisner , Tamas Matrai

Among other results, the paper gives new mapping theorems and new fixed point property theorems for inverse limits of inverse sequences of compact metric spaces with upper semicontinuous set-valued bonding functions. We also revisit the…

Dynamical Systems · Mathematics 2021-12-14 Iztok Banic , Goran Erceg , Judy Kennedy