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In this paper we characterize Birkhoff-James orthogonality of linear operators defined on a finite dimensional real Banach space $ \mathbb{X}. $ We also explore the symmetry of Birkhoff-James orthogonality of linear operators defined on $…

Functional Analysis · Mathematics 2016-07-29 Debmalya Sain

We study norm attainment for multilinear operators and homogeneous polynomials between Banach spaces, as well as for positive multilinear operators between Banach lattices. We establish multilinear and polynomial versions of [23, Theorem B]…

Functional Analysis · Mathematics 2026-05-13 Luis A. Garcia , José Lucas P. Luiz , Vinícius C. C. Miranda

We study symmetric points with respect to $(\rho_+)$-orthogonality, $(\rho_{-})$-orthogonality and $\rho$-orthogonality in the space $C(K, \mathbb{X}),$ where $K$ is a perfectly normal, compact space and $ \mathbb X$ is a Banach space. We…

Functional Analysis · Mathematics 2025-04-21 Shamim Sohel , Debmalya Sain , Kallol Paul

We initiate a study of structural properties of the quotient algebra $\mathcal K(X)/\mathcal A(X)$ of the compact-by-approximable operators on Banach spaces $X$ failing the approximation property. Our main results and examples include the…

Functional Analysis · Mathematics 2025-12-03 Hans-Olav Tylli , Henrik Wirzenius

In this article, we introduce the Lipschitz bounded approximation property for operator ideals. With this notion, we extend the original work done by Godefroy and Kalton and give some partial answers on the equivalence between the bounded…

Functional Analysis · Mathematics 2022-01-19 Geunsu Choi , Mingu Jung

Approximative properties of linear summation methods of Fourier series are considered in the Orlicz type spaces ${\mathcal S}_{M}$. In particular, in terms of approximations by such methods, constructive characteristics are obtained for…

Classical Analysis and ODEs · Mathematics 2019-10-29 Stanislav Chaichenko , Viktor Savchuk , Andrii Shidlich

We characterize left symmetric linear operators on a finite dimensional strictly convex and smooth real normed linear space $ \mathbb{X},$ which answers a question raised recently by one of the authors in \cite{S} [D. Sain,…

Functional Analysis · Mathematics 2024-07-30 Debmalya Sain , Puja Ghosh , Kallol Paul

We obtain the exact values of some important approximative quantities (such as, the best approximation, the basis width, Kolmogorov's width and the best $n$-term approximation) of certain sets of images of the diagonal operators in the…

Numerical Analysis · Mathematics 2016-10-03 Andriy L. Shidlich , Stanislav O. Chaichenko

We prove Carl's type inequalities for the error of approximation of compact sets K by deep and shallow neural networks. This in turn gives lower bounds on how well we can approximate the functions in K when requiring the approximants to…

Machine Learning · Statistics 2022-12-06 Guergana Petrova , Przemysław Wojtaszczyk

We provide comparison principles for convex functions through its proximal mappings. Consequently, we prove that the norm of the proximal operator determines a convex the function up to a constant. A new characterization of Lipschitzianity…

Optimization and Control · Mathematics 2020-07-30 Emilio Vilches

In this paper, by dilation technique on Schauder frames, we extend Godefroy and Kalton's approximation theorem (1997), and obtain that a separable Banach space has the $\lambda$-unconditional bounded approximation property ($\lambda$-UBAP)…

Functional Analysis · Mathematics 2025-07-04 Qiyao Bao , Rui Liu , Jie Shen

In this article we develop convergence theory for a general class of adaptive approximation algorithms for abstract nonlinear operator equations on Banach spaces, and use the theory to obtain convergence results for practical adaptive…

Numerical Analysis · Mathematics 2010-01-12 Michael Holst , Gantumur Tsogtgerel , Yunrong Zhu

The main result of the paper shows that, for 1<p and 1<=q, a linear operator T from l_p to l_q attains its norm if, and only if, there exists a not weakly null maximizing sequence for T (counterexamples can be easily constructed when p=1).…

Functional Analysis · Mathematics 2015-10-02 Daniel Pellegrino , Eduardo V. Teixeira

We consider similarity transformations of a perturbed linear operator $A-B$ in a complex Banach space $\mathcal{X}$, where the unperturbed operator $A$ is a generator of a Banach $L_1(\mathbb{R})$-module and the perturbation operator $B$ is…

Functional Analysis · Mathematics 2024-04-02 Anatoly G. Baskakov , Ilya A. Krishtal , Natalia B. Uskova

Let $L_0$ be a bounded operator on a Banach space, and consider a perturbation $L=L_0+K$, where $K$ is compact. This work is concerned with obtaining bounds on the number of eigenvalues of $L$ in subsets of the complement of the essential…

Spectral Theory · Mathematics 2015-01-09 Michael Demuth , Franz Hanauska , Marcel Hansmann , Guy Katriel

Several recent papers investigated unbounded convergences in Banach lattices. Combine all unbounded convergences, including unbounded order (norm, absolute weak, absolute weak*) convergence, we characterize L-weakly compact sets, L-weakly…

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

We study the Bishop-Phelps-Bollob\'as property for operators between Banach spaces. Sufficient conditions are given for generalized direct sums of Banach spaces with respect to a~uniformly monotone Banach sequence lattice to have the…

Functional Analysis · Mathematics 2021-06-14 M. D. Acosta , M. Mastyło , M. Soleimani-Mourchehkhorti

In this paper, we establish quantitative estimates for nonlinear sampling Kantorovich operators in terms of the modulus of continuity in the setting of Orlicz spaces. This general frame allows us to directly deduce some quantitative…

Functional Analysis · Mathematics 2021-02-18 Nursel Cetin , Danilo Costarelli , Gianluca Vinti

We study ergodicity of composition operators on rearrangement-invariant Banach function spaces. More precisely, we give a natural and easy-to-check condition on the symbol of the operator which entails mean ergodicity on a very large class…

Functional Analysis · Mathematics 2025-10-15 Thomas Kalmes , Dalimil Peša

In this paper we introduce the Stancu type generalization of the q-Bernstein-Schurer-Kantorovich operators and examine their approximation properties. We investigate the convergence of our operators with the help of the Korovkin's…

Classical Analysis and ODEs · Mathematics 2016-02-23 M. Mursaleen , Taqseer Khan