Displaying 41 – 60 of 104

Showing per page

Mesures spectrales de Walsh associées à certaines suites arithmétiques

Jean Coquet (1985)

Annales de l'institut Fourier

On associe à certaines suites g de nombres complexes une mesure borélienne positive μ g sur le tore dont la transformée de Fourier-Walsh est une suite de moyennes liées à g . La nature de μ g (discrète, continue) est discutée dans quelques cas : suites presque-périodiques et certaines suites arithmétiques.

Metric unconditionality and Fourier analysis

Stefan Neuwirth (1998)

Studia Mathematica

We investigate several aspects of almost 1-unconditionality. We characterize the metric unconditional approximation property (umap) in terms of “block unconditionality”. Then we focus on translation invariant subspaces L E p ( ) and C E ( ) of functions on the circle and express block unconditionality as arithmetical conditions on E. Our work shows that the spaces p E ( ) , p an even integer, have a singular behaviour from the almost isometric point of view: property (umap) does not interpolate between L E p ( ) and L E p + 2 ( ) . These...

Minimal ideals of group algebras

David Alexander, Jean Ludwig (2004)

Studia Mathematica

We first study the behavior of weights on a simply connected nilpotent Lie group G. Then for a subalgebra A of L¹(G) containing the Schwartz algebra 𝓢(G) as a dense subspace, we characterize all closed two-sided ideals of A whose hull reduces to one point which is a character.

Minimality and unique ergodicity for subgroup actions

Shahar Mozes, Barak Weiss (1998)

Annales de l'institut Fourier

Let G be an -algebraic semisimple group, H an algebraic -subgroup, and Γ a lattice in G . Partially answering a question posed by Hillel Furstenberg in 1972, we prove that if the action of H on G / Γ is minimal, then it is uniquely ergodic. Our proof uses in an essential way Marina Ratner’s classification of probability measures on G / Γ invariant under unipotent elements, and the study of “tubes” in G / Γ .

Mittelergodische Halbgruppen linearer Operatoren

Rainer J. Nagel (1973)

Annales de l'institut Fourier

A semigroup H in L s ( E ) , E a Banach space, is called mean ergodic, if its closed convex hull in L s ( E ) has a zero element. Compact groups, compact abelian semigroups or contractive semigroups on Hilbert spaces are mean ergodic.Banach lattices prove to be a natural frame for further mean ergodic theorems: let H be a bounded semigroup of positive operators on a Banach lattice E with order continuous norm. H is mean ergodic if there is a H -subinvariant quasi-interior point of E + and a H ' -subinvariant strictly...

Module maps over locally compact quantum groups

Zhiguo Hu, Matthias Neufang, Zhong-Jin Ruan (2012)

Studia Mathematica

We study locally compact quantum groups and their module maps through a general Banach algebra approach. As applications, we obtain various characterizations of compactness and discreteness, which in particular generalize a result by Lau (1978) and recover another one by Runde (2008). Properties of module maps on L ( ) are used to characterize strong Arens irregularity of L₁() and are linked to commutation relations over with several double commutant theorems established. We prove the quantum group...

Module ( ϕ , ψ ) -amenability of Banach algebras

Abasalt Bodaghi (2010)

Archivum Mathematicum

Let S be an inverse semigroup with the set of idempotents E and S / be an appropriate group homomorphic image of S . In this paper we find a one-to-one correspondence between two cohomology groups of the group algebra 1 ( S ) and the semigroup algebra 1 ( S / ) with coefficients in the same space. As a consequence, we prove that S is amenable if and only if S / is amenable. This could be considered as the same result of Duncan and Namioka [5] with another method which asserts that the inverse semigroup S is amenable...

Currently displaying 41 – 60 of 104