# Distances sets that are a shift of the integers and Fourier basis for planar convex sets

Abstract : The aim of this paper is to prove that if a planar set $A$ has a difference set $\Delta(A)$ satisfying $\Delta(A)\subset \Z^++s$ for suitable $s$ than $A$ has at most $3$ elements. This result is motivated by the conjecture that the disk has not more than $3$ orthogonal exponentials. Further, we prove that if $A$ is a set of exponentials mutually orthogonal with respect to any symmetric convex set $K$ in the plane with a smooth boundary and everywhere non-vanishing curvature, then $\# (A \cap {[-q,q]}^2) \leq C(K) q$ where $C(K)$ is a constant depending only on $K$. This extends and clarifies in the plane the result of Iosevich and Rudnev. As a corollary, we obtain the result from \cite{IKP01} and \cite{IKT01} that if $K$ is a centrally symmetric convex body with a smooth boundary and non-vanishing curvature, then $L^2(K)$ does not possess an orthogonal basis of exponentials.
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Article dans une revue
Acta Matematica Hungarica, 2008, 121, pp.107-118. 〈10.1007/s10474-008-7187-6〉

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https://hal.archives-ouvertes.fr/hal-00175046
Contributeur : Philippe Jaming <>
Soumis le : mercredi 26 septembre 2007 - 12:18:24
Dernière modification le : jeudi 3 mai 2018 - 15:32:06
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Alex Iosevich, Philippe Jaming. Distances sets that are a shift of the integers and Fourier basis for planar convex sets. Acta Matematica Hungarica, 2008, 121, pp.107-118. 〈10.1007/s10474-008-7187-6〉. 〈hal-00175046〉

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