{"title":"用单个函数和神经网络的移位和扩张的总和逼近","authors":"K. Shklyaev","doi":"10.1016/j.jat.2023.105915","DOIUrl":null,"url":null,"abstract":"<div><p>We find sufficient conditions on a function <span><math><mi>f</mi></math></span> to ensure that sums of functions of the form <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>α</mi><mi>x</mi><mo>−</mo><mi>θ</mi><mo>)</mo></mrow></mrow></math></span>, where <span><math><mrow><mi>α</mi><mo>∈</mo><mi>A</mi><mo>⊂</mo><mi>R</mi></mrow></math></span> and <span><math><mrow><mi>θ</mi><mo>∈</mo><mi>Θ</mi><mo>⊂</mo><mi>R</mi></mrow></math></span>, are dense in the real spaces <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>L</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span><span><span> on the real line or its compact subsets. That is, we consider </span>linear combinations in which all coefficients are 1. As a corollary we deduce results on density of sums of functions </span><span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>w</mi><mi>⋅</mi><mi>x</mi><mo>−</mo><mi>θ</mi><mo>)</mo></mrow></mrow></math></span>, <span><math><mrow><mi>w</mi><mo>∈</mo><mi>W</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></mrow></math></span>, <span><math><mrow><mi>θ</mi><mo>∈</mo><mi>Θ</mi><mo>⊂</mo><mi>R</mi></mrow></math></span> in <span><math><mrow><mi>C</mi><mrow><mo>(</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup><mo>)</mo></mrow></mrow></math></span> in the topology of uniform convergence on compact subsets.</p></div>","PeriodicalId":54878,"journal":{"name":"Journal of Approximation Theory","volume":null,"pages":null},"PeriodicalIF":0.9000,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Approximation by sums of shifts and dilations of a single function and neural networks\",\"authors\":\"K. Shklyaev\",\"doi\":\"10.1016/j.jat.2023.105915\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>We find sufficient conditions on a function <span><math><mi>f</mi></math></span> to ensure that sums of functions of the form <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>α</mi><mi>x</mi><mo>−</mo><mi>θ</mi><mo>)</mo></mrow></mrow></math></span>, where <span><math><mrow><mi>α</mi><mo>∈</mo><mi>A</mi><mo>⊂</mo><mi>R</mi></mrow></math></span> and <span><math><mrow><mi>θ</mi><mo>∈</mo><mi>Θ</mi><mo>⊂</mo><mi>R</mi></mrow></math></span>, are dense in the real spaces <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>L</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span><span><span> on the real line or its compact subsets. That is, we consider </span>linear combinations in which all coefficients are 1. As a corollary we deduce results on density of sums of functions </span><span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>w</mi><mi>⋅</mi><mi>x</mi><mo>−</mo><mi>θ</mi><mo>)</mo></mrow></mrow></math></span>, <span><math><mrow><mi>w</mi><mo>∈</mo><mi>W</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></mrow></math></span>, <span><math><mrow><mi>θ</mi><mo>∈</mo><mi>Θ</mi><mo>⊂</mo><mi>R</mi></mrow></math></span> in <span><math><mrow><mi>C</mi><mrow><mo>(</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup><mo>)</mo></mrow></mrow></math></span> in the topology of uniform convergence on compact subsets.</p></div>\",\"PeriodicalId\":54878,\"journal\":{\"name\":\"Journal of Approximation Theory\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.9000,\"publicationDate\":\"2023-07-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Approximation Theory\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0021904523000539\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Approximation Theory","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0021904523000539","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
Approximation by sums of shifts and dilations of a single function and neural networks
We find sufficient conditions on a function to ensure that sums of functions of the form , where and , are dense in the real spaces and on the real line or its compact subsets. That is, we consider linear combinations in which all coefficients are 1. As a corollary we deduce results on density of sums of functions , , in in the topology of uniform convergence on compact subsets.
期刊介绍:
The Journal of Approximation Theory is devoted to advances in pure and applied approximation theory and related areas. These areas include, among others:
• Classical approximation
• Abstract approximation
• Constructive approximation
• Degree of approximation
• Fourier expansions
• Interpolation of operators
• General orthogonal systems
• Interpolation and quadratures
• Multivariate approximation
• Orthogonal polynomials
• Padé approximation
• Rational approximation
• Spline functions of one and several variables
• Approximation by radial basis functions in Euclidean spaces, on spheres, and on more general manifolds
• Special functions with strong connections to classical harmonic analysis, orthogonal polynomial, and approximation theory (as opposed to combinatorics, number theory, representation theory, generating functions, formal theory, and so forth)
• Approximation theoretic aspects of real or complex function theory, function theory, difference or differential equations, function spaces, or harmonic analysis
• Wavelet Theory and its applications in signal and image processing, and in differential equations with special emphasis on connections between wavelet theory and elements of approximation theory (such as approximation orders, Besov and Sobolev spaces, and so forth)
• Gabor (Weyl-Heisenberg) expansions and sampling theory.