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Sets of p-multiplicity in locally compact groups

I. G. Todorov, L. Turowska (2015)

Studia Mathematica

We initiate the study of sets of p-multiplicity in locally compact groups and their operator versions. We show that a closed subset E of a second countable locally compact group G is a set of p-multiplicity if and only if E * = ( s , t ) : t s - 1 E is a set of operator p-multiplicity. We exhibit examples of sets of p-multiplicity, establish preservation properties for unions and direct products, and prove a p-version of the Stone-von Neumann Theorem.

Sidon sets and Riesz products

Jean Bourgain (1985)

Annales de l'institut Fourier

Let G be a compact abelian group and Γ the dual group. It is shown that if Δ Γ is a Sidon set, then the interpolating measures on Λ can be obtained as mean of Riesz products. If Λ is a Sidon set tending to infinity, Λ is of first type. Our approach yields in fact elementary proofs of certain characterizations of Sidonicity obtained in G. Pisier, C.R.A.S., Paris Ser. A, 286 (1978), 1003–1006 – Math. Anal. and Appl., Part B, Advances in Math., Suppl. Sts. vol. 7, 685-726 – preprint, using random Fourier...

Sigma-idéaux polaires et ensembles d'unicité dans les groupes abéliens localement compacts

Étienne Matheron (1996)

Annales de l'institut Fourier

On étend au cadre des groupes abéliens localement compacts certains résultats obtenus notamment par G. Debs, R. Kaufman, A. Kechris, A. Louveau et J. Saint Raymond sur la structure des fermés d’unicité et d’unicité au sens large du cercle unité. On montre également que de très nombreuses familles de compacts issues de l’Analyse Harmonique sont exactement de troisième classe dans la hiérarchie de Baire. Comme application, on donne une démonstration simple de l’existence d’ensembles de Dirichlet qui...

Some remarks on quasi-Cohen sets

Pascal Lefèvre, Daniel Li (2001)

Colloquium Mathematicae

We are interested in Banach space geometry characterizations of quasi-Cohen sets. For example, it turns out that they are exactly the subsets E of the dual of an abelian compact group G such that the canonical injection C ( G ) / C E c ( G ) L ² E ( G ) is a 2-summing operator. This easily yields an extension of a result due to S. Kwapień and A. Pełczyński. We also investigate some properties of translation invariant quotients of L¹ which are isomorphic to subspaces of L¹.

Some results on Kronecker, Dirichlet and Helson sets

Thomas-William Korner (1970)

Annales de l'institut Fourier

We construct the following: a perfect non Dirichlet set every proper closed subset of which is Kronecker, A weak Kronecker set which is not an R set; an independent countable Dirichlet set which is not Kronecker; a collection of q -disjoint Kronecker sets whose union is independent but Helson 1 / q ; A countable collection of disjoint Kronecker sets whose union is closed and independent but not Helson: a perfect independent Dirichlet set which is not Helson.

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