Convolution roots and differentiability of isotropic positive definite functions on spheres
نویسندگان
چکیده
منابع مشابه
Convolution Roots of Radial Positive Definite Functions with Compact Support
A classical theorem of Boas, Kac, and Krein states that a characteristic function φ with φ(x) = 0 for |x| ≥ τ admits a representation of the form φ(x) = ∫ u(y)u(y + x) dy, x ∈ R, where the convolution root u ∈ L2(R) is complex-valued with u(x) = 0 for |x| ≥ τ/2. The result can be expressed equivalently as a factorization theorem for entire functions of finite exponential type. This paper examin...
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1. Introduction. Let Sym denote the linear space of all symmetric second-order tensors on an n-dimensional real vector space Vect with scalar product. (If Vect is identified with R n , then Sym may be identified with the set of all symmetric n-by-n matrices.) A function f : Sym → R is said to be isotropic if f (A) = f (QAQ T) for all A ∈ Sym and all Q proper orthogonals. An isotropic function h...
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ژورنال
عنوان ژورنال: Proceedings of the American Mathematical Society
سال: 2014
ISSN: 0002-9939,1088-6826
DOI: 10.1090/s0002-9939-2014-11989-7