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A topological space $Y$ has the property (B) of Banakh if there is a countable family $\{A_n:n\in \mathbb{N}\}$ of closed nowhere dense subsets of $Y$ absorbing all compact subsets of $Y$. In this note we show that the space $C_p(X)$ of…

General Topology · Mathematics 2024-07-29 Mikołaj Krupski , Kacper Kucharski , Witold Marciszewski

We analyse and characterise the notion of lattice Lipschitz operator (a class of superposition operators, diagonal Lipschitz maps) when defined between Banach function spaces. After showing some general results, we restrict our attention to…

Functional Analysis · Mathematics 2024-06-07 Roger Arnau , Jose M. Calabuig , Ezgi Erdoğan , Enrique A. Sánchez Pérez

We solve some open problems regarding diameter two properties within the class of Banach spaces of real-valued Lipschitz functions by using the de Leeuw transform. Namely, we show that: the diameter two property, the strong diameter two…

Functional Analysis · Mathematics 2022-05-27 Rainis Haller , Andre Ostrak , Märt Põldvere

We study $p$-limited and almost $p$-limited sets in Banach lattices and their connections with relatively $p$-compact and relatively compact sets. We investigate the weak and the strong Gelfand-Phillips property of order $p$, as well as the…

Functional Analysis · Mathematics 2025-07-23 Halimeh Ardakani , Vinícius C. C. Miranda

Our purpose in this note is to investigate the order properties of positive operators from a locally convex space into its conjugate dual. We introduce a natural generalization of the Busch-Gudder strength function and we prove Kadison's…

Functional Analysis · Mathematics 2023-06-08 Zsigmond Tarcsay , Ábel Göde

The motive behind this manuscript is to set up the existence and uniqueness of a positive solution for a fractional thermostat model for certain values of the parameter $\lambda>0$. We accomplish sufficient conditions for the existence of a…

Functional Analysis · Mathematics 2017-10-05 Hiranmoy Garai , Lakshmi Kanta Dey , Ankush Chanda

In this paper, we study the basic properties of Toeplitz Operators with positive measures $\mu$ on harmonic Fock spaces. We prove equivalent conditions for boundedness, compactness and Schatten classes $S_{p}$ of $T_{\mu}$ by using the…

Functional Analysis · Mathematics 2024-10-10 Xue Gou , Xin Hu , Sui Huang

The powerful concept of an operator ideal on the class of all Banach spaces makes sense in the real and in the complex case. In both settings we may, for example, consider compact, nuclear, or $2$--summing operators, where the definitions…

Functional Analysis · Mathematics 2016-09-06 Joerg Wenzel

Let $C$ be a closed convex cone in a Banach ideal space $X$ on a measurable space with a $\sigma$-finite measure. We prove that conditions $C\cap X_+=\{0\}$ and $C\supset -X_+$ imply the existence of a strictly positive continuous…

Functional Analysis · Mathematics 2008-04-15 Dmitry B. Rokhlin

In this article, we study the relationship between \(p\)-\((V)\) subsets and p-\(V^*\) subsets of dual spaces. We investigate the Banach space X with the property that adjoint every \(p\)-convergent operator \(T: X \rightarrow Y\) is weakly…

Functional Analysis · Mathematics 2019-05-10 M. Alikhani

We extend the well-known Gelfand-Phillips property for Banach spaces to locally convex spaces, defining a locally convex space $E$ to be Gelfand-Phillips if every limited set in $E$ is precompact in the topology on $E$ defined by barrels.…

Functional Analysis · Mathematics 2021-11-15 Taras Banakh , Saak Gabriyelyan

Let $B(X)$ be the Banach algebra of all bounded linear operators acting on a Banach space $X$. Are sums and products of commuting decomposable operators on Banach spaces decomposable? This is one of the most important open problems in the…

Functional Analysis · Mathematics 2025-10-13 Salah Mecheri

A subspace $X$ of a Banach space $Y$ has $\textit{Property U}$ whenever every continuous linear functional on $X$ has a unique norm-preserving (i.e., Hahn$-$Banach) extension to $Y$ (Phelps, 1960). Throughout this document we introduce and…

Functional Analysis · Mathematics 2022-11-22 Ch. Cobollo , A. J. Guirao , V. Montesinos

We show that every maximally monotone operator of Fitzpatrick-Phelps type defined on a real Banach space must be of dense type. This provides an affirmative answer to a question posed by Stephen Simons in 2001 and implies that various…

Functional Analysis · Mathematics 2011-04-06 Heinz H. Bauschke , Jonathan M. Borwein , Xianfu Wang , Liangjin Yao

We prove that under suitable assumptions, the constant term in the Green function of the Paneitz-Branson operator on a compact Riemannian manifold $(M,g)$ is positive unless $(M,g)$ is conformally diffeomophic to the standard sphere. The…

Differential Geometry · Mathematics 2010-02-24 Emmanuel Humbert , Simon Raulot

We introduce and study Banach spaces which have property CWO, i.e., every finite convex combination of relatively weakly open subsets of their unit ball is open in the relative weak topology of the unit ball. Stability results of such…

Functional Analysis · Mathematics 2018-06-29 Trond Arnold Abrahamsen , Julio Becerra Guerrero , Rainis Haller , Vegard Lima , Märt Põldvere

We introduce a second numerical index for real Banach spaces with non-trivial Lie algebra, as the best constant of equivalence between the numerical radius and the quotient of the operator norm modulo the Lie algebra. We present a number of…

Functional Analysis · Mathematics 2020-04-01 Sun Kwang Kim , Han Ju Lee , Miguel Martin , Javier Meri

It is an open problem whether an infinite-dimensional amenable Banach algebra exists whose underlying Banach space is reflexive. We give sufficient conditions for a reflexive, amenable Banach algebra to be finite-dimensional (and thus a…

Functional Analysis · Mathematics 2007-05-23 Volker Runde

We investigate the spectral and index-theoretic properties of the Hodge-Dirac operator $D = \mathrm{d} + \mathrm{d}^*$ acting on the Banach space $\mathrm{L}^p(\Omega^\bullet(M))$ of differential forms over a compact Riemannian manifold…

Functional Analysis · Mathematics 2026-05-26 Cédric Arhancet

Given a Banach lattice $L,$ the space of lattice Lipschitz operators on $L$ has been introduced as a natural Lipschitz generalization of the linear notions of diagonal operator and multiplication operator on Banach function lattices. It is…

Functional Analysis · Mathematics 2024-11-19 Roger Arnau , Jose M. Calabuig , Enrique A. Sánchez-Pérez