A multiplier theorem for ultraspherical series
Let be a nonnegative Radon measure on which only satisfies for all , , with some fixed constants and In this paper, a new characterization for the space of Tolsa in terms of the John-Strömberg sharp maximal function is established.
The aim of this paper is to demonstrate how a fairly simple nilpotent Lie algebra can be used as a tool to study differential operators on with polynomial coefficients, especially when the property studied depends only on the degree of the polynomials involved and/or the number of variables.
We show that in every Polish, abelian, non-locally compact group G there exist non-Haar null sets A and B such that the set {g ∈ G; (g+A) ∩ B is non-Haar null} is empty. This answers a question posed by Christensen.
We prove that every homogeneous Carnot group can be lifted to a free homogeneous Carnot group. Though following the ideas of Rothschild and Stein, we give simple and self-contained arguments, providing a constructive proof, as shown in the examples.
Answering a question of Pisier, posed in [10], we construct an L-set which is not a finite union of translates of free sets.