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We present the current results in the study of weighted composition operators on weighted Banach spaces of an unbounded, locally finite metric space. Specifically, we determine characterizations of bounded and compact weighted composition…

Functional Analysis · Mathematics 2022-07-28 Robert F. Allen , Matthew A. Pons

Recently, the functionals different types of unbounded convergences (uo, un, uaw, uaw*) in Banach lattices were studied. In this paper, we study the continuous operators with respect to unbounded convergences. We first investigate the…

Functional Analysis · Mathematics 2021-04-06 Zhangjun Wang , Zili Chen , Jinxi Chen

This paper introduces a new definition of $\alpha$-monotone operators in real 2-uniformly convex and smooth Banach spaces. Based on this new definition, we establish several novel structural and analytical properties of such operators,…

Functional Analysis · Mathematics 2025-10-15 Changchi Huang , Jigen Peng , Yuchao Tang

We study Birkhoff-James orthogonality of compact (bounded) linear operators between Hilbert spaces and Banach spaces. Applying the notion of semi-inner-products in normed linear spaces and some related geometric ideas, we generalize and…

Functional Analysis · Mathematics 2018-10-12 Debmalya Sain , Kallol Paul , Arpita Mal

We introduce the class of unbounded $M$-weakly operators and the class of unbounded $L$-weakly compact operators. We investigate some properties for these new classification of operators and we study relation between them and $M$-weakly…

Functional Analysis · Mathematics 2021-09-16 Zahra Niktab , Kazem Haghnejad Azar , Razi Alavizadeh , Saba Sadeghi Gavgani

In this paper we explore the properties of a bounded linear operator defined on a Banach space, in light of operator norm attainment. Using Birkhoff-James orthogonality techniques, we give a necessary condition for a bounded linear operator…

Functional Analysis · Mathematics 2016-08-03 Debmalya Sain

We prove several abstract results giving general conditions under which subspaces of linear or multilinear operators on Banach spaces or Banach lattices are closed. Each of these abstract results is followed by concrete applications,…

Functional Analysis · Mathematics 2026-05-25 Geraldo Botelho , Ariel Monção

We characterize $k-$smoothness of bounded linear operators defined between infinite-dimensional Hilbert spaces. We study the problem in the setting of both finite and infinite-dimensional Banach spaces. We also characterize $k-$smoothness…

Functional Analysis · Mathematics 2024-08-14 Arpita Mal , Subhrajit Sey , Kallol Paul

We introduce and study a new class of nonlinear monotone operators acting in normal cones of real Banach spaces and possessing the property of strong concavity. We establish new constructive principles for the existence of nonzero fixed…

Functional Analysis · Mathematics 2026-04-27 Khachatur A. Khachatryan

A bounded linear operator $T$ on a Banach space $X$ is called frequently hypercyclic if there exists $x\in X$ such that the lower density of the set $\{n\in\N:T^nx\in U\}$ is positive for any non-empty open subset $U$ of $X$. Bayart and…

Functional Analysis · Mathematics 2012-09-07 Stanislav Shkarin

In this paper, we introduce and study a new classes of operators, named AM-unbounded norm compact operators. We study the the basic properties of the new operator and we investigate the lattice-order and topology property of the operator…

Functional Analysis · Mathematics 2019-10-07 Wang Zhangjun , Chen Zili , Chen Jinxi

We construct an indecomposable reflexive Banach space $X_{ius}$ such that every infinite dimensional closed subspace contains an unconditional basic sequence. We also show that every operator $T\in \mathcal{B}(X_{ius})$ is of the form…

Functional Analysis · Mathematics 2016-09-22 Spiros A. Argyros , A. Manoussakis

We provide a first-order necessary and sufficient condition for optimality of lower semicontinuous functions on Banach spaces using the concept of subdifferential. From the sufficient condition we derive that any subdifferential operator is…

Optimization and Control · Mathematics 2014-01-23 Florence Jules , Marc Lassonde

By strengthening one of the hypotheses of a well-known sufficient condition for the hypercyclicity of linear operators in Banach spaces, we arrive at a sufficient condition for linear chaos and reveal consequences of the latter for…

Functional Analysis · Mathematics 2021-07-23 Marat V. Markin

We show that operators on a separable infinite dimensional Banach space $X$ of the form $I +S$, where $S$ is an operator with dense generalised kernel, must lie in the norm closure of the hypercyclic operators on $X$, in fact in the closure…

Functional Analysis · Mathematics 2014-10-28 James Boland

In this paper, we introduce the concept of isotone cones in Banach spaces. Then we apply the order monotonic property of the metric projection operator to prove the existence of best approximations for some operators without continuity…

Optimization and Control · Mathematics 2017-10-27 Jinlu Li

Recently in [1] a new class of maximal monotone operators has been introduced. In this note we study domain range properties as well as connections with other classes and calculus rules for these operators we called strongly-representable.…

Functional Analysis · Mathematics 2008-02-26 M. D. Voisei , C. Zalinescu

Monotone operator theory and fixed point theory for nonexpansive mappings are central areas in modern nonlinear analysis and optimization. Although these areas are fairly well developed, almost all examples published are based on…

Functional Analysis · Mathematics 2018-05-25 Heinz H. Bauschke , Levi Miller , Walaa M. Moursi

In a recent paper (2024) Camacho, C\'{a}novas, Mart\'{\i}nez-Legaz and Parra introduced bimonotone operators, i.e., operators $T$ such that both $T$ and $-T$ are monotone, and found some interesting applications to convex feasibility…

Functional Analysis · Mathematics 2025-01-14 Nicolas Hadjisavvas

In this paper we study sufficient conditions for an operator to have an almost-invariant half-space. As a consequence, we show that if $X$ is an infinite-dimensional complex Banach space then every operator $T\in\mathcal{L}(X)$ admits an…

Functional Analysis · Mathematics 2015-10-06 Gleb Sirotkin , Ben Wallis