Positive Definite Functions
Mostrando 1-5 de 5 artigos, teses e dissertações.
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1. Positive integral operators and reproducing kernel Hilbert spaces / Operadores integrais positivos e espaços de Hilbert de reprodução
In this work we study theoretical properties of positive integral operators on L POT. 2(X; u), in the case when X is a topological space, either locally compact or first countable, and u is a strictly positive measure. The analysis is directed to spectral properties of the operator which are related to some extensions of Mercers Theorem and to the study of t
Publicado em: 2010
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2. Operadores integrais gerados por núcleos em multi-escalas / Integral operators generated by multi-scale kernels
We study Mercer like kernels, a very special class of positive definite kernels possessing the description given by many results labeled as Mercers Theorem. We explore some of their properties which are needed in the development of this work and construct their native space. In the second half of the work, we consider Mercer kernels defined by a multi-scale
Publicado em: 2009
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3. Funções positivas definidas para interpolação em esferas complexas. / Positive definite functions for interpolation on complex spheres.
Apresentamos uma caracterização das funções positivas definidas em esferas complexas, generalizando assim, um resultado de Schoenberg ([41]). Como no caso real, uma classe importante dessas funções é aquela composta pelas funções estritamente positivas definidas de uma certa ordem; estas podem ser utilizadas para resolver certos problemas de interpo
Publicado em: 2001
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4. The spectral domain of multivariate harmonizable processes
The spectral or frequency domain of a multivariate weakly harmonizable process is a vector space of vector functions that are integrable relative to a positive definite matrix bimeasure. It has a norm derived from a Gramian inner product. The completeness property of this space, which is needed for many applications, has been open for some years. An affirmat
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5. Delayed singularity formation for solutions of nonlinear partial differential equations in higher dimensions
Strict solutions u of genuinely nonlinear homogeneous hyperbolic equations in two independent variables with initial data f(x) of compact support become singular after a time interval of order ∥f∥-1. In higher dimensions solutions initially of compact support are likely to have life expectancies of orders ∥f∥-2+ε at least. This is proved for the spe