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Perron-Frobenius operators and the Klein-Gordon equation

Francisco Canto-Martín, Håkan Hedenmalm, Alfonso Montes-Rodríguez (2014)

Journal of the European Mathematical Society

For a smooth curve Γ and a set Λ in the plane 2 , let A C ( Γ ; Λ ) be the space of finite Borel measures in the plane supported on Γ , absolutely continuous with respect to the arc length and whose Fourier transform vanishes on Λ . Following [12], we say that ( Γ , Λ ) is a Heisenberg uniqueness pair if A C ( Γ ; Λ ) = { 0 } . In the context of a hyperbola Γ , the study of Heisenberg uniqueness pairs is the same as looking for uniqueness sets Λ of a collection of solutions to the Klein-Gordon equation. In this work, we mainly address the...

Principe d’Heisenberg et fonctions positives

Jean Bourgain, Laurent Clozel, Jean-Pierre Kahane (2010)

Annales de l’institut Fourier

On décrit un problème naturel concernant la transformation de Fourier. Soient f , f ^ deux fonctions associées par celle-ci, positives pour x a et nulles en zéro. Quelle est la borne inférieure pour a  ? En dimension supérieure, même question, l’intervalle étant remplacé par la boule de rayon a . On montre l’existence d’une borne inférieure strictement positive, qui est estimée en fonction de la dimension. La dernière section montre que cette question est naturellement liée à la théorie des fonctions zêta....

Restriction theorems for the Fourier transform to homogeneous polynomial surfaces in ℝ³

E. Ferreyra, T. Godoy, M. Urciuolo (2004)

Studia Mathematica

Let φ:ℝ² → ℝ be a homogeneous polynomial function of degree m ≥ 2, let Σ = (x,φ(x)): |x| ≤ 1 and let σ be the Borel measure on Σ defined by σ ( A ) = B χ A ( x , φ ( x ) ) d x where B is the unit open ball in ℝ² and dx denotes the Lebesgue measure on ℝ². We show that the composition of the Fourier transform in ℝ³ followed by restriction to Σ defines a bounded operator from L p ( ³ ) to L q ( Σ , d σ ) for certain p,q. For m ≥ 6 the results are sharp except for some border points.

Restrictions of Fourier transforms to curves

S. W. Drury (1985)

Annales de l'institut Fourier

Let x ( t ) = ( t , 1 2 t 2 , 1 6 t 3 ) a certain curve in R 3 . We investigate inequalities of the type { | f ^ ( x ( t ) ) | b d t } 1 / b C f a for f 𝒮 ( R 3). Our results improve improve an earlier restriction theorem of Prestini. Various generalizations are also discussed.

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