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In topological equivalence, a bounded linear operator between Banach spaces - we focus on the case of Hilbert spaces - is viewed as only acting linearly and continuously between them qua different spaces with the structure of linear…

Functional Analysis · Mathematics 2021-05-19 Eliahu Levy

It is observed that in Banach spaces, sectorial operators having bounded imaginary powers satisfy a Heinz-Kato inequality.

Functional Analysis · Mathematics 2020-08-18 Nikolaos Roidos

We consider the quasihyperbolic metric, and its generalizations in both the $n$-dimensional Euclidean space $R^n$, and in Banach spaces. Historical background, applications, and our recent work on convexity properties of these metrics are…

Complex Variables · Mathematics 2015-03-19 Riku Klén , Antti Rasila , Jarno Talponen

In scalar-valued Hardy space, the class of Schmidt subspaces for a bounded Hankel operator are closely related to nearly $S^*$-invariant subspaces, as described by G\'{e}rard and Pushnitski. In this article, we prove that these subspaces in…

Functional Analysis · Mathematics 2023-12-29 Arup Chattopadhyay , Soma Das , Chandan Pradhan

In this paper, we study spaceability of subsets of generalized Orlicz and Lebesgue spaces associated to Banach function space. Also, we give some sufficient conditions for spaceability of subsets of a general Banach space which improves an…

Functional Analysis · Mathematics 2022-08-09 Alireza Bagheri Salec , Stefan Ivkovic , Seyyed Mohammad Tabatabaie

In the paper is considered two problems on extension of operators whose range space for the first problem (or domain space for the second one) belongs to the fixed class of finite equivalence, which is generated by a given Banach space $X$.…

Functional Analysis · Mathematics 2007-05-23 Eugene Tokarev

There is a resent paper claiming that every hyponormal operator which is not a multiple of the identity (operator) has a nontrivial hyperinvariant subspace. If this claim is true, then every hyponormal operator has a nontrivial invariant…

Functional Analysis · Mathematics 2024-01-30 Junfeng Liu

This work is motivated by a question published in E. Glasner's paper On a question of Kazhdan and Yom Din regarding the possibility to approximate functionals on a Banach space which are almost invariant with respect to an action of a…

Functional Analysis · Mathematics 2025-06-10 Tomáš Raunig

We consider linear bounded operators acting in Banach spaces with a basis, such operators can be represented by an infinite matrix. We prove that for an invertible operator there exists a sequence of invertible finite-dimensional operators…

Functional Analysis · Mathematics 2024-03-12 Alexander Vasilyev , Vladimir Vasilyev , Abu Bakarr Kamanda Bongay

We discuss the concept of invariant subspaces for unbounded linear operators, point out some shortcomings of known definitions, and propose our own.

Functional Analysis · Mathematics 2025-05-13 M. I. Belishev , S. A. Simonov

In [2] we characterized in terms of a quadratic growth condition various metric regularity properties of the subdifferential of a lower semicontinuous convex function acting in a Hilbert space. Motivated by some recent results in [16] where…

Optimization and Control · Mathematics 2015-07-01 Francisco J. Aragón Artacho , Michel H. Geoffroy

We characterize the relatively compact subsets of $L^1\left(\| m \| \right),$ the quasi-Banach function space associated to the semivariation of a given vector measure $m$ showing that the strong connection between compactness, uniform…

Functional Analysis · Mathematics 2019-10-30 Ricardo del Campo , Antonio Fernández , Fernando Mayoral , Francisco Naranjo

We estimate the number of small eigenvalues of Schr\"odinger operators on Riemannian vector bundles over geometrically finite manifolds.

Differential Geometry · Mathematics 2024-12-24 Werner Ballmann , Panagiotis Polymerakis

We identify symmetric quasi-Banach range of the discrete Calder\'{o}n operator and Hilbert transform acting on a symmetric quasi-Banach sequence space. As an application we present an example of optimal range in the case when the domain of…

Functional Analysis · Mathematics 2019-08-27 K. S. Tulenov

In this paper we study a class of quasi--variational--hemi\-va\-ria\-tio\-nal inequalities in reflexive Banach spaces. The inequalities contain a convex potential, a locally Lipschitz superpotential, and a solution-dependent set of…

Dynamical Systems · Mathematics 2023-09-12 S. Migorski , JC. Yao , SD. Zeng

The concept of adjusted sublevel set for a quasiconvex function was introduced in \cite{AuHa05} and the local existence of a norm-to-weak$^*$ upper semicontinuous base-valued submap of the normal operator associated to the adjusted sublevel…

Optimization and Control · Mathematics 2023-01-31 Marco Castellani , Massimiliano Giuli

In this paper, the weighted estimates for multilinear pseudo-differential operators were systematically studied in rearrangement invariant Banach and quasi-Banach spaces. These spaces contain the Lebesgue space, the classical Lorentz space…

Classical Analysis and ODEs · Mathematics 2023-12-21 Jiawei Tan , Qingying Xue

We give new proofs that some Banach spaces have Pe{\l}czy\'nski's property $(V)$.

Functional Analysis · Mathematics 2009-04-21 Pascal Lefèvre , Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza

We construct an infinite dimensional Banach space of continuous functions C(K) such that every one-to-one operator on C(K) is onto.

Functional Analysis · Mathematics 2014-06-30 Antonio Avilés , Piotr Koszmider

We address the existence of non-trivial closed invariant subspaces of operators $T$ on Banach spaces whenever their square $T^2$ have or, more generally, whether there exists a polynomial $p$ with $\mbox{deg}(p)\geq 2$ such that the lattice…

Functional Analysis · Mathematics 2024-09-04 Maximiliano Contino , Eva Gallardo-Gutierrez