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We present a systematic study of the family of positive definite (p.d.) kernels with the use of their associated feature maps and feature spaces. For a fixed set $X$, generalizing Loewner, we make precise the corresponding partially ordered…

Functional Analysis · Mathematics 2025-01-22 Palle E. T. Jorgensen , James Tian

We use the notion of $\A$-compact sets, which are determined by a Banach operator ideal $\A$, to show that most classic results of certain approximation properties and several Banach operator ideals can be systematically studied under this…

Functional Analysis · Mathematics 2012-12-14 Silvia Lassalle , Pablo Turco

Building on the work of \.{I}nan and of Almahariq--Peters--Vergili, we develop an axiomatic framework for approximate algebra based on an algebra-compatible closure operator $\Phi^{\!*}$ on a unital ring. The operator is assumed to be…

Commutative Algebra · Mathematics 2026-04-29 Dang Vo Phuc

The $p$-adic unitary operator $U$ is defined as an invertible operator on $p$-adic ultrametric Banach space such that $\left |U\right |=\left |U^{-1}\right |=1$. We point out $U$ has a spectral measure valued in $\textbf{projection…

Mathematical Physics · Physics 2023-11-03 Zhao Tianhong

We prove new summability properties for multilinear operators on $\ell_p$ spaces. An important tool for this task is a better understanding of the interplay between almost summing and absolutely summing multilinear operators.

Functional Analysis · Mathematics 2014-04-07 O. Blasco , G. Botelho , D. Pellegrino , P. Rueda

The approximate representation of operators by finite matrices is analysed in terms of accuracy and convergence. The identity operator, for example, can be reconstructed using a basis of harmonic oscillator states leading to a narrow peak…

Mathematical Physics · Physics 2025-12-02 B. G. Giraud , S. Karataglidis , K. Murulane , R. Peschanski

A complete characterization of the similarity between two operator-valued multishifts with invertible operator weights is obtained purely in terms of operator weights. This generalizes several existing results of the unitary equivalence of…

Functional Analysis · Mathematics 2024-01-23 Soumitra Ghara , Surjit Kumar , Shailesh Trivedi

We prove matching direct and inverse theorems for (algebraic) polynomial approximation with doubling weights $w$ having finitely many zeros and singularities (i.e., points where $w$ becomes infinite) on an interval and not too ``rapidly…

Classical Analysis and ODEs · Mathematics 2015-07-20 Kirill A. Kopotun

Several unitarily invariant norm inequalities and numerical radius inequalities for Hilbert space operators are studied. We investigate some necessary and sufficient conditions for the parallelism of two bounded operators. For a finite rank…

Functional Analysis · Mathematics 2024-04-03 Pintu Bhunia

The Operator axioms have produced new real numbers with new operators. New operators naturally produce new equations and thus extend the traditional mathematical models which are selected to describe various scientific rules. So new…

Numerical Analysis · Computer Science 2021-02-08 Pith Peishu Xie

The study of operator algebras on Hilbert spaces, and C*-algebras in particular, is one of the most active areas within Functional Analysis. A natural generalization of these is to replace Hilbert spaces (which are $L^2$-spaces) with…

Functional Analysis · Mathematics 2019-10-09 Eusebio Gardella

We show that for a linear space of operators ${\mathcal M}\subseteq {\mathcal B}(H_1,H_2)$ the following assertions are equivalent. (i) ${\mathcal M} $ is reflexive in the sense of Loginov--Shulman. (ii) There exists an order-preserving map…

Operator Algebras · Mathematics 2015-11-26 Janko Bračič , Lina Oliveira

We describe a new operator space structure on $L_p$ when $p$ is an even integer and compare it with the one introduced in our previous work using complex interpolation. For the new structure, the Khintchine inequalities and Burkholder's…

Operator Algebras · Mathematics 2013-07-23 Gilles Pisier

In this paper we solve the following problems: (i) find two differential operators P and Q satisfying [P,Q]=P, where P flows according to the KP hierarchy \partial P/\partial t_n = [(P^{n/p})_+,P], with p := \ord P\ge 2; (ii) find a matrix…

High Energy Physics - Theory · Physics 2016-09-06 M. Adler , A. Morozov , T. Shiota , P. van Moerbeke

In this paper, we investigate Durrmeyer-type generalizations of maximum-minimum neural network operators. The primary objective of this study is to establish the convergence of these operators in the $L^{p}$ norm for functions $f\in…

Numerical Analysis · Mathematics 2026-02-02 Berke Şahin , İsmail Aslan

Researchers have identified complex matrices $A$ such that a bounded linear operator $B$ acting on a Hilbert space will admit a dilation of the form $A \otimes I$ whenever the numerical range inclusion relation $W(B) \subseteq W(A)$ holds.…

Functional Analysis · Mathematics 2019-11-05 Chi-Kwong Li , Yiu-Tung Poon

We consider the continuous superposition of operators of the form \[ \iint_{[0, 1]\times (1, N)} (-\Delta)_p^s \,u\,d\mu(s,p), \] where $\mu$ denotes a signed measure over the set $[0, 1]\times (1, N)$, joined to a nonlinearity satisfying a…

Analysis of PDEs · Mathematics 2026-03-12 Serena Dipierro , Edoardo Proietti Lippi , Caterina Sportelli , Enrico Valdinoci

Fractional operators are widely used in mathematical models describing abnormal and nonlocal phenomena. Although there are extensive numerical methods for solving the corresponding model problems, theoretical analysis such as the regularity…

Numerical Analysis · Mathematics 2020-06-30 Lijing Zhao , Weihua Deng , Jan S Hesthaven

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

In this paper, we introduce Durrmeyer type modification of Meyer-Konig-Zeller operators based on (p,q)-integers. Rate of convergence of these operators are explored with the help of Korovkin type theorems. We establish some direct results…

Classical Analysis and ODEs · Mathematics 2017-06-23 Honey Sharma , Cheena Gupta , Ramapati Maurya