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We establish a spectral characterization theorem for the operators on complex Hilbert spaces of arbitrary dimensions that attain their norm on every closed subspace. The class of these operators is not closed under addition. Nevertheless,…

Functional Analysis · Mathematics 2016-07-13 Satish K. Pandey , Vern I. Paulsen

In this paper we compute Lawson homology groups and semi-topological K-theory for some threefolds and fourfolds. We consider smooth complex projective varieties whose zero cycles are supported on a proper subvariety. Rationally connected…

K-Theory and Homology · Mathematics 2007-05-23 Mircea Voineagu

In this article, we give a representation for compact operators acting between reflexive Banach spaces, which generalizes the representation given by Edmunds et al. for compact operators between reflexive Banach spaces with strictly convex…

Functional Analysis · Mathematics 2023-08-16 G. Ramesh , M. Veena Sangeetha , Shanola S. Sequeira

We obtain new uniqueness theorems for harmonic functions defined on the unit disc or in the half plane. These results are applied to obtain new resolvent descriptions of spectral subspaces of polynomially bounded groups of operators on…

Complex Variables · Mathematics 2010-03-16 Alexander Borichev , Yuri Tomilov

Let $T:Y\to X$ be a bounded linear operator between two normed spaces. We characterize compactness of $T$ in terms of differentiability of the Lipschitz functions defined on $X$ with values in another normed space $Z$. Furthermore, using a…

Functional Analysis · Mathematics 2019-10-17 Mohammed Bachir , Gonzalo Flores , Sebastián Tapia-García

In this paper, we study compact complex orbifolds. In the first part, we shows the equivalence of two notions of compact K\"ahler orbifold. In the second part, we shows various versions of Demailly's regularisation theorems for compact…

Algebraic Geometry · Mathematics 2023-02-24 Xiaojun Wu

For a proper, cocompact action by a locally compact group of the form $H \times G$, with $H$ compact, we define an $H \times G$-equivariant index of $H$-transversally elliptic operators, which takes values in $KK_*(C^*H, C^*G)$. This…

K-Theory and Homology · Mathematics 2020-06-24 Peter Hochs , Hang Wang

This paper is devoted to the study of two classes of operators related to disjointly weakly compact sets, which we call $DW$-DP operators and $DW$-limited operators, respectively. They carry disjointly weakly compact subsets of a Banach…

Functional Analysis · Mathematics 2024-12-03 Jin Xi Chen , Jingge Feng

Every new inner product in a Hilbert space is obtained from the original one by means of a unique positive operator$.$ The first part of the paper is a survey on applications of such a technique, including a characterization of similarity…

Functional Analysis · Mathematics 2020-10-29 C. S. Kubrusly , B. P. Duggal

Let $K$ be a positive compact operator on a Banach lattice. We prove that if either $[K>$ or $<K]$ is ideal irreducible then $[K>=<K]=L_+(X)\cap {K}'$. We also establish the Perron-Frobenius Theorem for such operators $K$. Finally we apply…

Functional Analysis · Mathematics 2012-08-20 Niushan Gao

We study best approximations to compact operators between Banach spaces and Hilbert spaces, from the point of view of Birkhoff-James orthogonality and semi-inner-products. As an application of the present study, some distance formulae are…

Functional Analysis · Mathematics 2021-04-30 Debmalya Sain

We characterize the polynomial decay of orbits of Hilbert space $C_0$-semigroups in resolvent terms. We also show that results of the same type for general Banach space semigroups and functions obtained recently in the paper by C.J.K.Batty…

Functional Analysis · Mathematics 2009-10-07 Alexander Borichev , Yuri Tomilov

We obtain exhaustive results and treat in a unified way the question of boundedness, compactness, and weak compactness of composition operators from the Bloch space into any space from a large family of conformally invariant spaces that…

Functional Analysis · Mathematics 2016-11-07 Manuel D. Contreras , Santiago Diaz-Madrigal , Dragan Vukotic

We introduce a class of operators which is called unbounded Dunford-Pettis. In this paper, we study some properties of the operators, relationships with the other classes of operators and the space of these operators.

Functional Analysis · Mathematics 2019-09-25 Wang Zhangjun , Chen Zili , Chen Jinxi , Ouyang Miao

A continuous operator $T$ between two Banach lattices $E$ and $F$ is called almost order-weakly compact, whenever for each almost order bounded subset $A$ of $E$, $T(A)$ is a relatively weakly compact subset of $F$. In Theorem 4, we show…

Functional Analysis · Mathematics 2022-01-10 Mina Matin , Mina Matin , Kazem Haghnejad Azar , Ali Ebadi

Motivated by the equivalent definition of a continuous operator between Banach spaces in terms of weakly null nets, we introduce two types of continuous operators between Banach lattices using unbounded absolute weak convergence. We…

Functional Analysis · Mathematics 2020-04-07 Omid Zabeti

We prove that a separable Banach space $E$ does not contain a copy of the space $\co$ of null-sequences if and only if for every doubly power-bounded operator $T$ on $E$ and for every vector $x\in E$ the relative compactness of the sets…

Functional Analysis · Mathematics 2013-01-29 Bálint Farkas

We introduce and study the class of almost limited sets in Banach lattices, that is, sets on which every disjoint weak$^{*}$ null sequence of functionals converges uniformly to zero. It is established that a Banach lattice has order…

Functional Analysis · Mathematics 2013-09-10 Jin Xi Chen , Zi Li Chen , Guo Xing Ji

We describe boundedness and compactness properties for the operators obtained by the Weyl-Pedersen calculus in the case of the irreducible unitary representations of nilpotent Lie groups that are associated with flat coadjoint orbits. We…

Analysis of PDEs · Mathematics 2013-10-22 Ingrid Beltita , Daniel Beltita

We extend a classical theorem of Courr\`{e}ge to Lie groups in a global setting, thus characterising all linear operators on the space of smooth functions of compact support that satisfy the positive maximum principle. We show that these…

Functional Analysis · Mathematics 2019-07-31 David Applebaum , Trang Le Ngan