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We introduce a class of (tuples of commuting) unbounded operators on a Banach space, admitting smooth functional calculi, that contains all operators of Helffer-Sj\"ostrand type and is closed under the action of smooth proper mappings.…

Spectral Theory · Mathematics 2016-08-16 Mats Andersson , Håkan Samuelsson , Sebastian Sandberg

We investigate lineability/spaceability problems within the setting of multilinear summing operators on quasi-Banach sequence spaces. Furthermore, we deal with the contemporary geometric notions of pointwise-lineability and…

Functional Analysis · Mathematics 2023-03-28 Nacib Gurgel Albuquerque , Lindinês Coleta

Motivated by a general dilation theory for operator-valued measures, framings and bounded linear maps on operator algebras, we consider the dilation theory of the above objects with special structures. We show that every operator-valued…

Functional Analysis · Mathematics 2014-11-18 Deguang Han , David R. Larson , Bei Liu , Rui Liu

The boundedness (continuity) of composition operators from some function space to another one is significant, though there are few results about this problem. Thus, in this study, we provide necessary and sufficient conditions on the…

Functional Analysis · Mathematics 2024-09-18 Naoya Hatano , Masahiro Ikeda , Ryota Kawasumi

We show that the existence of a strongly convex function with a Lipschitz derivative on a Banach space already implies that the space is isomorphic to a Hilbert space. Similarly, if both a function and its convex conjugate are $C^2$ then…

Functional Analysis · Mathematics 2025-06-11 Nicolas Borchard , Gerd Wachsmuth

We study extension theorems for Lipschitz-type operators acting on metric spaces and with values on spaces of integrable functions. Pointwise domination is not a natural feature of such spaces, and so almost everywhere inequalities and…

Functional Analysis · Mathematics 2019-10-02 W. V. Cavalcante , P. Rueda , E. A. Sánchez-Pérez

We conjecture that whenever $M$ is a metric space of density at most continuum, then the space of Lipschitz functions is $w^*$-separable. We prove the conjecture for several classes of metric spaces including all the Banach spaces with a…

Functional Analysis · Mathematics 2025-03-14 Leandro Candido , Marek Cuth , Benjamin Vejnar

We consider linear operators defined on a subspace of a complex Banach space into its topological antidual acting positively in a natural sense. The goal of this paper is to investigate of this kind of operators. The main theorem is a…

Functional Analysis · Mathematics 2014-09-12 Zoltán Sebestyén , Zsolt Szűcs , Zsigmond Tarcsay

We extend the concept of average expansivity for operators on Banach spaces to operators on arbitrary locally convex spaces. We obtain complete characterizations of the average expansive weighted shifts on Fr\'echet sequence spaces.…

Functional Analysis · Mathematics 2026-03-10 Nilson C. Bernardes , Félix Martínez-Giménez , Francisco Rodenas

We explore the norm attainment set and the minimum norm attainment set of a bounded linear operator between Hilbert spaces and Banach spaces. Indeed, we obtain a complete characterization of both the sets, separately for operators between…

Functional Analysis · Mathematics 2024-08-13 Debmalya Sain , Kallol Paul , Kalidas Mandal

Orlicz spaces are generalizations of Lebesgue spaces. The sufficient and necessary conditions for generalized H\"{o}lder's inequality in Lebesgue spaces and in weak Lebesgue spaces are well known. The aim of this paper is to present…

Functional Analysis · Mathematics 2018-09-05 Ifronika , Al Azhary Masta , Muhammad Nur , Hendra Gunawan

The dynamics of weighted translation operators on Lebesgue spaces, Orlicz spaces, and in general on solid Banach function spaces have been studied in numerous papers. Recently, the dynamics of weighted translations on weighted Orlicz spaces…

Functional Analysis · Mathematics 2025-11-25 Stefan Ivkovic

We give embedding theorems for weighted Bergman-Orlicz spaces on the ball and then apply our results to the study of composition operators in this context. As one of the motivations of this work, we show that there exist some weighted…

Functional Analysis · Mathematics 2010-12-06 Stéphane Charpentier

We study properties of continuous semi-homogeneous operators of degree $k$ via various functions (e.g. measures of noncompactness) on all bounded subsets of a Banach space. We prove necessary and sufficient conditions for these functions to…

Functional Analysis · Mathematics 2015-08-19 Nina A. Erzakova

We describe the proper closed invariant subspaces of the integration operator when it acts continuously on countable intersections and countable unions of weighted Banach spaces of holomorphic functions on the unit disc or the complex…

Functional Analysis · Mathematics 2020-04-07 José Bonet , Antonio Galbis

It is proved that a commutative algebra $A$ of operators in a reflexive real Banach space has an invariant subspace if each operator $T\in A$ satisfies the condition $$\|1- \varepsilon T^2\|_e \le 1 + o(\varepsilon) \text{ when }…

Functional Analysis · Mathematics 2016-12-20 Victor Lomonosov , Victor Shulman

We establish necessary and sufficient conditions for boundedness of composition operators on the most general class of Hilbert spaces of entire Dirichlet series with real frequencies. Depending on whether or not the space contains any…

Complex Variables · Mathematics 2017-10-11 Minh Luan Doan , Le Hai Khoi

We obtain a pointwise description of functions belonging to function spaces with the lattice property. In particular, it is valid for Banach function spaces provided that the Hardy-Littlewood maximal operator is bounded. We also study…

Functional Analysis · Mathematics 2020-08-13 Pankaj Jain , Anastasia Molchanova , Monika Singh , Sergey Vodopyanov

An algebra A of operators on a Banach space X is called strictly semi-transitive if for all non-zero x,y in X there exists an operator S in A such that Sx=y or Sy=x. We show that if A is norm-closed and strictly semi-transitive, then every…

Functional Analysis · Mathematics 2007-05-23 H. P. Rosenthal , V. G. Troitsky

In this paper the general spectral properties of linear operators in Banach spaces are studied. We find sufficient conditions on structure of Banach spaces and resolvent properties that guarantee completeness of roots elements of Schatten…

Analysis of PDEs · Mathematics 2017-06-06 Veli Shakhmurov