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We study the analog of semi-separable integral kernels in $\cH$ of the type {equation*} K(x,x')={cases} F_1(x)G_1(x'), & a<x'< x< b, \\ F_2(x)G_2(x'), & a<x<x'<b, {cases} {equation*} where $-\infty\leq a<b\leq \infty$, and for a.e.\ $x \in…

Functional Analysis · Mathematics 2014-04-23 Alan Carey , Fritz Gesztesy , Denis Potapov , Fedor Sukochev , Yuri Tomilov

We present a novel and mathematically transparent approach to function approximation and the training of large, high-dimensional neural networks, based on the approximate least-squares solution of associated Fredholm integral equations of…

Numerical Analysis · Mathematics 2024-07-17 Patrick Gelß , Aizhan Issagali , Ralf Kornhuber

Given a pair of self-adjoint operators $H$ and $V$ such that $V$ is bounded and $(H+V-i)^{-1}-(H-i)^{-1}$ belongs to the Schatten-von Neumann ideal $\mathcal{S}^n$, $n\ge 2$, of operators on a separable Hilbert space, we establish higher…

Functional Analysis · Mathematics 2022-11-17 Teun D. H. van Nuland , Anna Skripka

We prove a uniform vector-valued Wiener-Wintner Theorem for a class of operators that includes compositions of ergodic Koopman operators with contractive multiplication operators. Our results are new even in the case of complex-valued…

Functional Analysis · Mathematics 2025-03-20 Micky Barthmann , Sohail Farhangi

We suggest a new algorithm to estimate representations of compact Lie groups from finite samples of their orbits. Different from other reported techniques, our method allows the retrieval of the precise representation type as a direct sum…

Optimization and Control · Mathematics 2025-09-23 Henrique Ennes , Raphaël Tinarrage

For every multivariable polynomial $p$, with $p(0)=1$, we construct a determinantal representation $$p=\det (I - K Z),$$ where $Z$ is a diagonal matrix with coordinate variables on the diagonal and $K$ is a complex square matrix. Such a…

Functional Analysis · Mathematics 2012-08-14 Anatolii Grinshpan , Dmitry S. Kaliuzhnyi-Verbovetskyi , Hugo J. Woerdeman

The aim of this note is to generalize the notion of Fredholm operator to an arbitrary $C^*$-algebra. Namely, we define "finite type" elements in an axiomatic way, and also we define Fredholm type element $a$ as such element of a given…

Operator Algebras · Mathematics 2018-01-09 Dragoljub J. Kečkić , Zlatko Lazović

The purpose of this paper is to push forward the theory of operator-valued Riemann Hilbert problems and demonstrate their effectiveness in respect to the implementation of a non-linear steepest descent method \textit{\'{a} la} Deift-Zhou.…

Mathematical Physics · Physics 2014-11-06 A. R. Its , K. K. Kozlowski

Let $\mathcal{H}$ be a separable Hilbert space and let $A^{2}_{\varphi}(\mathcal{H})$ be the $\mathcal{H}$-valued Bergman spaces with exponential weights. In the present paper, we give the complete characterizations for the boundedness and…

Functional Analysis · Mathematics 2023-05-29 Jian-xiang Dong , Yu-feng Lu

We define classes of pseudodifferential operators on $G$-bundles with compact base and give a generalized $L^2$ Fredholm theory for invariant operators in these classes in terms of von Neumann's $G$-dimension. We combine this formalism with…

Analysis of PDEs · Mathematics 2011-04-14 Joe J. Perez

Let $A_{\alpha}^{p}(\mathbb{B}^n;\mathbb{C}^d)$ be the weighted Bergman space on the unit ball $\mathbb{B}^n$ of $\mathbb{C}^n$ of functions taking values in $\mathbb{C}^d$. For $1<p<\infty$ let $\mathcal{T}_{p,\alpha}$ be the algebra…

Classical Analysis and ODEs · Mathematics 2016-02-08 Robert S. Rahm , Brett D. Wick

It is shown that each linear operator on a separable Hilbert space which generates a finite type I von Neumann algebra has, up to unitary equivalence, a unique representation as a direct integral of inflations of mutually unitary…

Functional Analysis · Mathematics 2017-05-26 Piotr Niemiec

We investigate the norm of sums of independent vector-valued random variables in noncommutative Lp spaces. This allows us to obtain a uniform family of complete embeddings of the Schatten class Sq^n in Sp(lq^m) with optimal order m = n^2.…

Functional Analysis · Mathematics 2007-05-23 Marius Junge , Javier Parcet

We consider a new algorithm in light of the min-max Collatz-Wielandt formalism to compute the principal eigenvalue and the eigenvector (eigen-function) for a class of positive Perron-Frobenius-like operators. Such operators are natural…

Numerical Analysis · Mathematics 2021-11-25 Dong Li , Jianan Li

We affirmatively settle the question on existence of a real-valued higher order spectral shift function for a pair of self-adjoint operators $H$ and $V$ such that $V$ is bounded and $V(H-iI)^{-1}$ belongs to a Schatten-von Neumann ideal…

Functional Analysis · Mathematics 2022-08-25 Teun D. H. van Nuland , Anna Skripka

We obtain a number of explicit estimates for quasi-norms of pseudo-differential operators in the Schatten-von Neumann classes $S_q$ with $0<q\le 1$. The estimates are applied to derive semi-classical bounds for operators with smooth or…

Spectral Theory · Mathematics 2022-01-27 Alexander V. Sobolev

We extend our previous definition of K-theoretic invariants for operator systems based on hermitian forms to higher K-theoretical invariants. We realize the need for a positive parameter $\delta$ as a measure for the spectral gap of the…

Operator Algebras · Mathematics 2024-11-06 Walter D. van Suijlekom

Let $G$ be a compact Lie group acting smoothly on a smooth, compact manifold $M$, let $P \in \psi^m(M; E_0, E_1)$ be a $G$--invariant, classical pseudodifferential operator acting between sections of two vector bundles $E_i \to M$, $i =…

Functional Analysis · Mathematics 2020-12-29 Alexandre Baldare , Rémi Côme , Victor Nistor

We characterize the compactness of composition operators; in term of generalized Nevanlinna counting functions, on a large class of Hilbert spaces of analytic functions, which can be viewed between the Bergman and the Dirichlet spaces

Functional Analysis · Mathematics 2010-05-02 Karim Kellay , Pascal Lefèvre

Backstepping design for boundary linear PDE is formulated as a convex optimization problem. Some classes of parabolic PDEs and a first-order hyperbolic PDE are studied, with particular attention to non-strict feedback structures. Based on…

Systems and Control · Computer Science 2017-10-11 Pedro Ascencio , Alessandro Astolfi , Thomas Parisini