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Characterizing the function spaces defined by neural networks helps understanding the corresponding learning models and their inductive bias. While in some limits neural networks correspond to function spaces that are Hilbert spaces, these…

Machine Learning · Statistics 2025-08-22 Francesca Bartolucci , Ernesto De Vito , Lorenzo Rosasco , Stefano Vigogna

We introduce a nonstandard extension of the category of diffeological spaces, and demonstrate its application to the study of generalized functions. Just as diffeological spaces are defined as concrete sheaves on the site of Euclidean open…

Algebraic Topology · Mathematics 2025-07-10 Kazuhisa Shimakawa

Let $p\in(0,1)$, $\alpha:=1/p-1$ and, for any $\tau\in [0,\infty)$, $\Phi_{p}(\tau):=\tau/(1+\tau^{1-p})$. Let $H^p(\mathbb R^n)$, $h^p(\mathbb R^n)$ and $\Lambda_{n\alpha}(\mathbb{R}^n)$ be, respectively, the Hardy space, the local Hardy…

Classical Analysis and ODEs · Mathematics 2021-03-10 Yangyang Zhang , Dachun Yang , Wen Yuan

In this paper, thanks to the generalizations of the dual spaces of the Hardy-amalgam spaces $\mathcal H^{(q,p)}$ and $\mathcal{H}_{\mathrm{loc}}^{(q,p)}$ for $0<q\leq1$ and $q\leq p<\infty$, obtained in our earlier paper, we prove that the…

Analysis of PDEs · Mathematics 2021-03-09 Zobo Vincent de Paul Ablé , Justin Feuto

This paper studies the probabilistic function approximation problem over reproducing kernel Hilbert spaces. We show the existence and uniqueness of the optimizer under mild assumptions. Furthermore, we generalize the celebrated representer…

Functional Analysis · Mathematics 2025-07-16 Dongwei Chen , Kai-Hsiang Wang

The modeling of fracture problems within geometrically linear elasticity is often based on the space of generalized functions of bounded deformation $GSBD^p(\Omega)$, $p\in(1,\infty)$, their treatment is however hindered by the very low…

Analysis of PDEs · Mathematics 2019-12-13 Sergio Conti , Matteo Focardi , Flaviana Iurlano

Let $\mathbb B_n$ be the open unit ball in $\mathbb C^n$. We characterize the spectra of pointwise multipliers $M_u$ acting on Banach spaces of analytic functions on $\mathbb B_n$ satisfying some general conditions. These spaces include…

Functional Analysis · Mathematics 2020-02-18 Mikael Lindström , Santeri Miihkinen , David Norrbo

Let $(\mathcal{X},d,\mu)$ be a doubling metric measure space in the sense of R. R. Coifman and G. Weiss, $L$ a non-negative self-adjoint operator on $L^2(\mathcal{X})$ satisfying the Davies--Gaffney estimate, and $X(\mathcal{X})$ a ball…

Functional Analysis · Mathematics 2023-04-28 Xiaosheng Lin , Dachun Yang , Sibei Yang , Wen Yuan

We obtain a new general extension theorem in Banach spaces for operators which are not required to be symmetric, and apply it to obtain Harnack estimates and a priori regularity for solutions of fractional powers of several second order…

Analysis of PDEs · Mathematics 2016-10-12 Hugo Aimar , Gastón Beltritti , Ivana Gómez , Cristian Rios

Using the technique of enrichment of contractive type mappings by Krasnoselskij averaging, presented here for the first time, we introduce and study the class of {\it enriched nonexpansive mappings} in Hilbert spaces. In order to…

Functional Analysis · Mathematics 2019-09-06 Vasile Berinde

In this paper we introduce a reproducing kernel Hilbert space defined on $\mathbb{R}^{d+1}$ as the tensor product of a reproducing kernel defined on the unit sphere $\mathbb{S}^{d}$ in $\mathbb{R}^{d+1}$ and a reproducing kernel defined on…

Numerical Analysis · Mathematics 2015-12-24 Johann S. Brauchart , Josef Dick , Lou Fang

The theory of slice regular functions of a quaternionic variable, introduced in 2006 by Gentili and Struppa, extends the notion of holomorphic function to the quaternionic setting. This fast growing theory is already rich of many results…

Complex Variables · Mathematics 2015-03-17 Chiara de Fabritiis , Graziano Gentili , Giulia Sarfatti

We study the radially symmetric high dimensional Fisher-KPP nonlocal diffusion equation with free boundary, and reveal some fundamental differences from its one dimensional version considered in \cite{cdjfa} recently. Technically, this high…

Analysis of PDEs · Mathematics 2021-02-11 Yihong Du , Wenjie Ni

We develop sampling formulas for high-dimensional functions in reproducing kernel Hilbert spaces, where we rely on irregular samples that are taken at determining sequences of data points. We place particular emphasis on sampling formulas…

Machine Learning · Computer Science 2025-04-21 Armin Iske , Lennart Ohlsen

Higher transcendental function occur frequently in the calculation of Feynman integrals in quantum field theory. Their expansion in a small parameter is a non-trivial task. We report on a computer program which allows the systematic…

Mathematical Physics · Physics 2008-11-26 Stefan Weinzierl

We consider a space of infinitely smooth functions on an unbounded closed convex set in ${\mathbb R}^n$. It is shown that each function of this space can be extended to an entire function in ${\mathbb C}^n$ satisfying some prescribed growth…

Complex Variables · Mathematics 2009-08-19 I. Kh. Musin , P. V. Fedotova

An extension of reproducing kernel Hilbert space (RKHS) theory provides a new framework for modeling functional regression models with functional responses. The approach only presumes a general nonlinear regression structure as opposed to…

Statistics Theory · Mathematics 2008-12-17 Heng Lian

The aim of this article is to give a complete solution to the problem of the bilinear decompositions of the products of some Hardy spaces $H^p(\mathbb{R}^n)$ and their duals in the case when $p<1$ and near to $1$, via wavelets, paraproducts…

Classical Analysis and ODEs · Mathematics 2016-03-22 Jun Cao , Luong Dang Ky , Dachun Yang

The fully matricial generalization in part I, of the difference quotient derivation on holomorphic functions, in which ${\mathbb C}$ is replaced by a Banach algebra $B$, is extended from the affine case to a Grassmannian completion. The…

Operator Algebras · Mathematics 2009-04-28 Dan-Virgil Voiculescu

In this paper, we establish a suitable version of the Hahn-Banach theorem within the framework of Colombeau spaces, a class of spaces used to model generalized functions. Our approach addresses the case where maps are defined…

Functional Analysis · Mathematics 2024-10-14 Djamel eddine Kebiche , Paolo Giordano