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Spectral pairs in cartesian coordinates
Journal article   Peer reviewed

Spectral pairs in cartesian coordinates

Palle Jorgensen and Steen Pedersen
The Journal of Fourier Analysis and Applications, Vol.5(4), pp.285-302
07/1999
DOI: 10.1007/BF01259371

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Abstract

Let Ω ⊂ℝd have finite positive Lebesgue measure, and let $$\mathcal{L}^2$$ (Ω) be the corresponding Hilbert space of $$\mathcal{L}^2$$ -functions on Ω. We shall consider the exponential functionse λ on Ω given bye λ(x)=e i2πλ·x . If these functions form an orthogonal basis for $$\mathcal{L}^2$$ (Ω), when λ ranges over some subset Λ in ℝ d , then we say that (Ω, Λ) is a spectral pair, and that Λ is a spectrum. We conjecture that (Ω, Λ) is a spectral pair if and only if the translates of some set Ω′ by the vectors of Λ tile ℝd. In the special case of Ω=Id, the d-dimensional unit cube, we prove this conjecture, with Ω′=Id, for d≤3, describing all the tilings by Id, and for all d when Λ is a discrete periodic set. In an appendix we generalize the notion of spectral pair to measures on a locally compact abelian group and its dual.
spectral resolution Signal, Image and Speech Processing operator extensions Mathematics spectral pair induced representations tilings Abstract Harmonic Analysis Fourier Analysis 47C05 translations Approximations and Expansions Hilbert space Applications of Mathematics 46L55 Partial Differential Equations 42C05 22D25 Fourier basis

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