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A characterization of Fourier transforms

Philippe Jaming (2010)

Colloquium Mathematicae

The aim of this paper is to show that, in various situations, the only continuous linear (or not) map that transforms a convolution product into a pointwise product is a Fourier transform. We focus on the cyclic groups ℤ/nℤ, the integers ℤ, the torus 𝕋 and the real line. We also ask a related question for the twisted convolution.

A characterization of the minimal strongly character invariant Segal algebra

Viktor Losert (1980)

Annales de l'institut Fourier

For a locally compact, abelian group G , we study the space S 0 ( G ) of functions on G belonging locally to the Fourier algebra and with l 1 -behavior at infinity. We give an abstract characterization of the family of spaces { S 0 ( G ) : G abelian } by its hereditary properties.

A Freĭman-type theorem for locally compact abelian groups

Tom Sanders (2009)

Annales de l’institut Fourier

Suppose that G is a locally compact abelian group with a Haar measure μ . The δ -ball B δ of a continuous translation invariant pseudo-metric is called d -dimensional if μ ( B 2 δ ) 2 d μ ( B δ ) for all δ ( 0 , δ ] . We show that if A is a compact symmetric neighborhood of the identity with μ ( n A ) n d μ ( A ) for all n d log d , then A is contained in an O ( d log 3 d ) -dimensional ball, B , of positive radius in some continuous translation invariant pseudo-metric and μ ( B ) exp ( O ( d log d ) ) μ ( A ) .

A property of Fourier Stieltjes transforms on the discrete group of real numbers

Yngve Domar (1970)

Annales de l'institut Fourier

Let μ be a Fourier-Stieltjes transform, defined on the discrete real line and such that the corresponding measure on the dual group vanishes on the set of characters, continuous on R . Then for every ϵ > 0 , { x R | Re ( μ ( x ) ) > ϵ } has a vanishing interior Lebesgue measure. If ϵ = 0 the statement is not generally true. The result is applied to prove a theorem of Rosenthal.

An elementary proof of the decomposition of measures on the circle group

Przemysław Ohrysko (2015)

Colloquium Mathematicae

We give an elementary proof for the case of the circle group of the theorem of O. Hatori and E. Sato, which states that every measure on a compact abelian group G can be decomposed into a sum of two measures with a natural spectrum and a discrete measure.

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