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1.
Stephen J. Sangwine 《Mathematical Methods in the Applied Sciences》2017,40(1):22-30
A vector‐valued signal in N dimensions is a signal whose value at any time instant is an N‐dimensional vector, that is, an element of . The sum of an arbitrary number of such signals of the same frequency is shown to trace an ellipse in N‐dimensional space, that is, to be confined to a plane. The parameters of the ellipse (major and minor axes, represented by N‐dimensional vectors; and phase) are obtained algebraically in terms of the directions of oscillation of the constituent signals, and their phases. It is shown that the major axis of the ellipse can always be determined algebraically. That is, a vector, whose value can be computed algebraically (without decisions or comparisons of magnitude) from parameters of the constituent signals, always represents the major axis of the ellipse. The ramifications of this result for the processing and Fourier analysis of signals with vector values or samples are discussed, with reference to the definition of Fourier transforms, particularly discrete Fourier transforms, such as have been defined in several hypercomplex algebras, including Clifford algebras. The treatment in the paper, however, is entirely based on signals with values in . Although the paper is written in terms of vector signals (which are taken to include images and volumetric images), the analysis clearly also applies to a superposition of simple harmonic motions in N dimensions. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
2.
In Sook Park 《Mathematische Nachrichten》2008,281(4):561-574
It is shown that for any locally compact abelian group ?? and 1 ≤ p ≤ 2, the Fourier type p norm with respect to ?? of a bounded linear operator T between Banach spaces, denoted by ‖T |?????p‖, satisfies ‖T |?????p‖ ≤ ‖T |?????p‖, where ?? is the direct product of ?2, ?3, ?4, … It is also shown that if ?? is not of bounded order then Cnp ‖T |?????p‖ ≤ ‖T |?????p‖, where ?? is the circle group, n is a onnegative integer and Cp = . From these inequalities, for any locally compact abelian group ?? ‖T |?????2‖ ≤ ‖T |?????2‖, and moreover if ?? is not of bounded order then ‖T |?????2‖ = ‖T |?????2‖. The Hilbertian property and B‐convexity are discussed in the framework of Fourier type p norms. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
José Garcí a-Cuerva José Manuel Marco Javier Parcet 《Transactions of the American Mathematical Society》2003,355(9):3591-3609
Sharp Fourier type and cotype of Lebesgue spaces and Schatten classes with respect to an arbitrary compact semisimple Lie group are investigated. In the process, a local variant of the Hausdorff-Young inequality on such groups is given.
4.
Operator-valued Fourier Multipliers on Periodic Triebel Spaces 总被引:2,自引:0,他引:2
Shang Quan BU Jin Myong KIM 《数学学报(英文版)》2005,21(5):1049-1056
We establish operator-valued Fourier multiplier theorems on periodic Triebel spaces, where the required smoothness of the multipliers depends on the indices of the Triebel spaces. This is used to give a characterization of the maximal regularity in the sense of Triebel spaces for Cauchy problems with periodic boundary conditions. 相似文献
5.
The main purpose of this paper is to study the validity of theHausdorffYoung inequality for vector-valued functionsdefined on a non-commutative compact group. As we explain inthe introduction, the natural context for this research is thatof operator spaces. This leads us to formulate a whole new theoryof Fourier type and cotype for the category of operator spaces.The present paper is the first step in this program, where thebasic theory is presented, the main examples are analyzed andsome important questions are posed. 2000 Mathematics SubjectClassification 43A77, 46L07. 相似文献
6.
The present article applies the method of Geometric Analysis to the study H ‐type groups satisfying the J2 condition and finishes the series of works describing the Heisenberg group and the quaternion H ‐type group. The latter class of H ‐type groups satisfying the J2 condition is related to the octonions. The relations between the group structure and the boundary of the corresponding Siegel upper half space are given. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
We investigate analytical properties of a measure geometric Laplacian which is given as the second derivative w.r.t. two atomless finite Borel measures μ and ν with compact supports supp μ ? supp ν on the real line. This class of operators includes a generalization of the well‐known Sturm‐Liouville operator as well as of the measure geometric Laplacian given by . We obtain for this differential operator under both Dirichlet and Neumann boundary conditions similar properties as known in the classical Lebesgue case for the euclidean Laplacian like Gauß‐Green‐formula, inversion formula, compactness of the resolvent and its kernel representation w.r.t. the corresponding Green function. Finally we prove nuclearity of the resolvent and give two representations of its trace. 相似文献
8.
Nico Spronk 《Proceedings of the American Mathematical Society》2002,130(12):3609-3617
We show that for any locally compact group , the Fourier algebra is operator weakly amenable.
9.
Peter J. Wood 《Proceedings of the American Mathematical Society》2003,131(6):1881-1890
In this paper, we study the ideals in the Fourier algebra of a locally compact group which are complemented by an invariant projection. In particular we show that when is discrete, every ideal which is complemented by a completely bounded projection must be invariantly complemented. Perhaps surprisingly, this result does not depend of the amenability of the group or the algebra, but instead relies on the operator biprojectivity of the Fourier algebra for a discrete group.
10.
In this paper we show that if is an amenable locally compact group and if is a closed subgroup, then the ideal has an approximate identity of norm If is not open, this bound is the best possible.
11.
A linear and bounded operator T between Banach spaces X and Y has Fourier type 2 with respect to a locally compact abelian group G if there exists a constant c > 0 such that∥T ∥2 ≤ c∥f∥2 holds for all X‐valued functions f ∈ LX2(G) where is the Fourier transform of f. We show that any Fourier type 2 operator with respect to the classical groups has Fourier type 2 with respect to any locally compact abelian group. This generalizes previous special results for the Cantor group and for closed subgroups of ?n. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
定义了齐型空间上的 Riesz位势算子 Iβ ,并研究了它的 L ipschitz有界性等性质 . 相似文献
13.
Andrei Agrachev 《Journal of Functional Analysis》2009,256(8):2621-2655
We present an invariant definition of the hypoelliptic Laplacian on sub-Riemannian structures with constant growth vector using the Popp's volume form introduced by Montgomery. This definition generalizes the one of the Laplace-Beltrami operator in Riemannian geometry. In the case of left-invariant problems on unimodular Lie groups we prove that it coincides with the usual sum of squares.We then extend a method (first used by Hulanicki on the Heisenberg group) to compute explicitly the kernel of the hypoelliptic heat equation on any unimodular Lie group of type I. The main tool is the noncommutative Fourier transform. We then study some relevant cases: SU(2), SO(3), SL(2) (with the metrics inherited by the Killing form), and the group SE(2) of rototranslations of the plane. 相似文献
14.
In this paper, we define the quadratic-phase Fourier wavelet transform (QPFWT) and discuss its basic properties including convolution for QPFWT. Further, inversion formula and the Parseval relation of QPFWT are also discussed. Continuity of QPFWT on some function spaces are studied. Moreover, some applications of quadratic-phase Fourier transform (QPFT) to solve the boundary value problems of generalized partial differential equations. 相似文献
15.
Let X be a Banach space. We show that each m : ? \ {0} → L (X ) satisfying the Mikhlin condition supx ≠0(‖m (x )‖ + ‖xm ′(x )‖) < ∞ defines a Fourier multiplier on B s p,q (?; X ) if and only if 1 < p < ∞ and X is isomorphic to a Hilbert space; each bounded measurable function m : ? → L (X ) having a uniformly bounded variation on dyadic intervals defines a Fourier multiplier on B s p,q (?; X ) if and only if 1 < p < ∞ and X is a UMD space. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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17.
Several results about convolution and about Fourier coefficients for X-valued functions defined on t he torus satisfying the condition sup ||y||=1∫-π^π|| B (f (e^iθ), y)||dθ/2π〈 ∞ for a bounded bilinear map B : X × Y → Z are presented and some applications are given. 相似文献
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19.
M. Laczkovich G. Szé kelyhidi 《Proceedings of the American Mathematical Society》2005,133(6):1581-1586
Let be an Abelian group and let denote the linear space of all complex-valued functions defined on equipped with the product topology. We prove that the following are equivalent.
(i) Every nonzero translation invariant closed subspace of contains an exponential; that is, a nonzero multiplicative function.
(ii) The torsion free rank of is less than the continuum.
20.
G. A. Karagulyan 《Mathematical Notes》2002,71(3-4):362-373
In this paper we study the properties of the maximal operator generated by the Calderón--Zygmund operator. In particular, we refine Hunt's inequality. 相似文献