Results 1 to 10 of about 86 (83)

Isometric Reflection Vectors and Characterizations of Hilbert Spaces [PDF]

Journal of Function Spaces, 2014
A known characterization of Hilbert spaces via isometric reflection vectors is based on the following implication: if the set of isometric reflection vectors in the unit sphere SX of a Banach space X has nonempty interior in SX, then X is a Hilbert space.
Donghai Ji, Senlin Wu
doaj   +2 more sources

On an EVI curve characterization of Hilbert spaces

Journal of Mathematical Analysis and Applications, 2012
Given the \(\alpha\)-convex functional \(\varphi\) on the Banach space \((X,\|\cdot\|)\), the authors consider the solution \(t\mapsto u(t)\) of the gradient flow of \(\varphi\) fulfilling a so-called evolution variational inequality of the form \[ {1\over 2} e^{\alpha t}\| u(t)- z\|^2-{1\over 2} e^{\alpha s}\| u(s)-z\|^2\leq(\varphi(z)- \varphi(u(t)))
Jonas M Tolle
exaly   +2 more sources

Some Characterizations of Finite-Dimensional Hilbert Spaces

Journal of Mathematical Analysis and Applications, 1998
The main result of the paper is: if each extreme point of the unit ball of the space of operators on a finite-dimensional normed linear space \(X\) is an isometry, then the space \(X\) is isometric to a Hilbert space (of the corresponding dimension). The converse statement is well-known.
exaly   +3 more sources

New characterizations of reproducing kernel Hilbert spaces and applications to metric geometry [PDF]

Opuscula Mathematica, 2021
We give two new global and algorithmic constructions of the reproducing kernel Hilbert space associated to a positive definite kernel. We further present a general positive definite kernel setting using bilinear forms, and we provide new examples.
Daniel Alpay, Palle E.T. Jorgensen
doaj   +1 more source

Approximative K-atomic decompositions and frames in Banach spaces [PDF]

Arab Journal of Mathematical Sciences, 2020
L. Gǎvruţa (2012) introduced a special kind of frames, named K-frames, where K is an operator, in Hilbert spaces, which is significant in frame theory and has many applications.
Shah Jahan
doaj   +1 more source

Controlled g-frames and dual g-frames in Hilbert spaces

Journal of Inequalities and Applications, 2023
As generalizations of g-frames and controlled frames, the theory of controlled g-frames has been deeply studied. This paper addresses the controlled g-frames and dual g-frames in Hilbert spaces.
Hui-Min Liu, Yan-Ling Fu, Yu Tian
doaj   +1 more source

A characterization of spectral operators on Hilbert spaces [PDF]

Proceedings of the American Mathematical Society, 1984
In [ 8 ] Wadhwa shows that if a bounded linear operator T T on a complex Hilbert ...
Tanahashi, Kôtarô, Yoshino, Takashi
openaire   +2 more sources

Controlled K-Fusion Frame for Hilbert Spaces

Moroccan Journal of Pure and Applied Analysis, 2021
K-fusion frames are a generalization of fusion frames in frame theory. In this paper, we extend the concept of controlled fusion frames to controlled K-fusion frames, and we develop some results on the controlled K-fusion frames for Hilbert spaces, which
Assila Nadia, Kabbaj Samir, Moalige Brahim   +2 more
doaj   +1 more source

Some New Notions of Bases for the Range of Operators in Hilbert Spaces [PDF]

Sahand Communications in Mathematical Analysis
This paper is devoted to introduce a new concept of bases for the range of the operator $K$. Actually, we consider controlled $K$-orthonormal and controlled $K$-Riesz bases which are a generalization of ordinary bases in Hilbert spaces. In the sequel, we
Hessam Hosseinnezhad
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On the well-posedness of differential quasi-variational-hemivariational inequalities

Open Mathematics, 2020
The goal of this paper is to discuss the well-posedness and the generalized well-posedness of a new kind of differential quasi-variational-hemivariational inequality (DQHVI) in Hilbert spaces.
Cen Jinxia, Min Chao, Nguyen Van Thien, Tang Guo-ji   +3 more
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