Given an uncountable, compact metric space X, we show that there exists no reproducingkernelhilbert space that contains the space of all continuous functions on X.
Given an uncountable, compact metric space X, we show that there exists no reproducingkernelhilbert space that contains the space of all continuous functions on X.
In 1961, Bargmann introduced the classical Fock space F(C), and in 1984, Cholewinsky introduced the generalized Fock space F-2,F-nu (C). These two spaces are the aim of many works, and have many applications in mathem...
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In 1961, Bargmann introduced the classical Fock space F(C), and in 1984, Cholewinsky introduced the generalized Fock space F-2,F-nu (C). These two spaces are the aim of many works, and have many applications in mathematics, in physics, and in quantum mechanics. In this work, we introduce and study the reproducingkernelhilbert space F-r,F-alpha(C) associated with the Bessel operator B-r,B-alpha of r-order (r >= 3). Next, we establish an uncertainty inequality of Heisenberg type for the space F-r,F-alpha (C). Finally, using the theory of extremal functions, we give best approximate inversion formulas for the difference operator D and the integral operator P, respectively.
A straightforward way to represent the kernel approximant of a function, known by a finite set of samples, within a reproducingkernelhilbert space is through the canonical dual pair. The canonical dual pair consists...
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A straightforward way to represent the kernel approximant of a function, known by a finite set of samples, within a reproducingkernelhilbert space is through the canonical dual pair. The canonical dual pair consists of the basis of kernel translates and the corresponding Lagrange basis. From a numerical perspective, one is particularly interested in dual pairs such that the dual basis is quasi-local meaning that it can be well approximated using only a small subset of the data sites. This implies that the inverse Gramian is approximately sparse. In this case, the kernel approximant is efficiently computable by multiplying a sparse matrix with the data vector. We present two methods for finding such quasi-localized dual bases. First, we adapt the idea of localizing the Lagrange basis, which yields an approximate canonical dual pair and extend this idea to derive a new, symmetric preconditioner for kernel matrices. Second, we use samplets to obtain multiresolution versions of dual bases. Samplets are localized discrete signed measures constructed such that their respective measure integrals of polynomials up to a certain degree vanish. Therefore, the kernel matrix and its inverse are compressible to sparse matrices in samplet coordinates for asymptotically smooth kernels. We provide benchmark experiments in two spatial dimensions to demonstrate the compression power of both approaches and apply the new preconditioner to implicit surface reconstruction in computer graphics.
We propose a new topological clustering methodology, based on generalizing an empirical risk minimization framework, using a reproducingkernelhilbert space (RKHS) for vectorized persistent homology representations o...
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We propose a new topological clustering methodology, based on generalizing an empirical risk minimization framework, using a reproducingkernelhilbert space (RKHS) for vectorized persistent homology representations of point clouds. In contrast to conventional Euclidean-based clustering methods which address only pairwise similarity among data points, our new approach of topological K-means clusters data based on similarity of shapes which are exhibited by the local vicinity of each data point at multiple scales. Thereby, topological clustering systematically captures the inherent local and global higher order data characteristics that are otherwise inaccessible with Euclidean-based clustering. We summarize the extracted shape characteristics of each local vicinity in the form of a persistence diagram (PD) and embed the PDs into a RKHS, which induces a distance among shapes of local vicinities in hilbert space. Our derived theoretical guarantees on stability and consistency of the topological partitions are the first theoretical results of this kind at the intersection of topological data analysis and statistical inference. Additionally, we establish a number of new theoretical results on bounds of covering numbers in hilbertspaces which are of independent interest in statistical learning theory. We demonstrate the superior performance of the new topological K-means clustering on simulations and the US COVID-19 data.
Given a Banach space E consisting of functions, we ask whether there exists a reproducingkernelhilbert space H with bounded kernel such that E subset of H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackag...
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Given a Banach space E consisting of functions, we ask whether there exists a reproducingkernelhilbert space H with bounded kernel such that E subset of H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E\subset H$$\end{document}. More generally, we consider the question, whether for a given Banach space consisting of functions F with E subset of F\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E\subset F$$\end{document}, there exists an intermediate reproducingkernelhilbert space E subset of H subset of F\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E\subset H\subset F$$\end{document}. We provide both sufficient and necessary conditions for this to hold. Moreover, we show that for typical classes of function spaces described by smoothness there is a strong dependence on the underlying dimension: the smoothness s required for the space E needs to grow proportional to the dimension d in order to allow for an intermediate reproducingkernelhilbert space H.
We propose a new data-driven approach for learning the fundamental solutions (Green's functions) of various linear partial differential equations (PDEs) given sample pairs of input-output functions. Building off t...
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We propose a new data-driven approach for learning the fundamental solutions (Green's functions) of various linear partial differential equations (PDEs) given sample pairs of input-output functions. Building off the theory of functional linear regression (FLR), we estimate the best-fit Green's function and bias term of the fundamental solution in a reproducingkernelhilbert space (RKHS) which allows us to regularize their smoothness and impose various structural constraints. We derive a general representer theorem for operator RKHSs to approximate the original infinite-dimensional regression problem by a finite-dimensional one, reducing the search space to a parametric class of Green's functions. In order to study the prediction error of our Green's function estimator, we extend prior results on FLR with scalar outputs to the case with functional outputs. Finally, we demonstrate our method on several linear PDEs including the Poisson, Helmholtz, Schrodinger, Fokker-Planck, and heat equation. We highlight its robustness to noise as well as its ability to generalize to new data with varying degrees of smoothness and mesh discretization without any additional training.
We study reproducing kernel hilbert spaces (RKHS) on a Riemannian manifold. In particular, we discuss under which condition Sobolev spaces are RKHS and characterize their reproducingkernels. Further, we introduce and...
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We study reproducing kernel hilbert spaces (RKHS) on a Riemannian manifold. In particular, we discuss under which condition Sobolev spaces are RKHS and characterize their reproducingkernels. Further, we introduce and discuss a class of smoother RKHS that we call diffusion spaces. We illustrate the general results with a number of detailed examples. While connections between Sobolev spaces, differential operators and RKHS are well known in the Euclidean setting, here we present a self-contained study of analogous connections for Riemannian manifolds. By collecting a number of results in unified a way, we think our study can be useful for researchers interested in the topic.
This article studies the distributed parameter system that governs adaptive estimation by mobile sensor networks of external fields in a reproducingkernelhilbert space (RKHS). The article begins with the derivation ...
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This article studies the distributed parameter system that governs adaptive estimation by mobile sensor networks of external fields in a reproducingkernelhilbert space (RKHS). The article begins with the derivation of conditions that guarantee the well-posedness of the ideal, infinite dimensional governing equations of evolution for the centralized estimation scheme. Subsequently, convergence of finite dimensional approximations is studied. Rates of convergence in all formulations are established using history-dependent bases defined from translates of the RKHS kernel that are centered at sample points along the agent trajectories. Sufficient conditions are derived that ensure that the finite dimensional approximations of the ideal estimator equations converge at a rate that is bounded by the fill distance of samples in the agents' assigned subdomains. The article concludes with examples of simulations and experiments that illustrate the qualitative performance of the introduced algorithms.
This note consists of two largely independent parts. In the first part we give conditions on the kernel k : Omega x Omega -> R of a reproducingkernelhilbert space H continuously embedded via the identity mapping ...
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This note consists of two largely independent parts. In the first part we give conditions on the kernel k : Omega x Omega -> R of a reproducingkernelhilbert space H continuously embedded via the identity mapping into L-2(Omega, mu), which are equivalent to the fact that H is even compactly embedded into L-2(Omega, mu). In the second part we consider a scenario from infinite-variate L-2-approximation. Suppose that the embedding of a reproducingkernelhilbert space of univariate functions with reproducingkernel 1 + k into L-2(Omega, mu) is compact. We provide a simple criterion for checking compactness of the embedding of a reproducingkernelhilbert space with the kernel given by Sigma(u is an element of U) gamma(u) circle times(j is an element of u)k where U = {u subset of N : |u| < infinity}, and gamma = (gamma(u))(u is an element of U) is a family of non-negative numbers, into an appropriate L-2 space.
The concept of reproducingkernelhilbert space does not capture the key features of the spherical smoothing problem. A semi- reproducingkernelhilbert space (SRKHS), provides a more natural setting for the smoothing...
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The concept of reproducingkernelhilbert space does not capture the key features of the spherical smoothing problem. A semi- reproducingkernelhilbert space (SRKHS), provides a more natural setting for the smoothing spline solution. In this paper, we carry over the concept of the SRKHS from the R-d to the sphere, Sd-1. In addition, a systematic study is made of the properties of an spherical SRKHS. Next, we present the one to one correspondence between increment-reproducingkernels and conditionally positive definite functions and its consequences on spherical optimal smoothing. The smoothing and interpolation issues on the sphere are considered in the proposed SRKHS setting. Finally, a simulation study is done to illustrate the proposed methodology and an analysis of world average temperature from 1963 to 1967 and 1993-1997 is done using the proposed methods.
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