arXiv subjects
Publications and source records attributed to N. Asmar.
In a celebrated paper, Burkholder, Gundy, and Silverstein used Brownian motion to derive a maximal function characterization of H^p spaces for 0 < p < infinity. In this paper, we show that their method extends to higher dimensions and yields a dimension-free weak type (1,1) estimate for a conjugate function on the N-dimensional torus.
We introduce the notion of an ACF space, that is, a space for which a generalized version of M. Riesz's theorem for conjugate functions with values in the Banach space is bounded. We use transference to prove that spaces for which the Hilbert transform is bounded, iė\. $X\in\text{HT}$, are ACF spaces. We then show that Bourgain's proof of $X\in\text{HT}\implies X\in\text{UMD}$ is a consequence of this result.
Let $Σ$ be a $σ$-algebra over $Ω$, and let $M(Σ)$ denote the Banach space of complex measures. Consider a representation $T_t$ for $t\in\Bbb R$ acting on $M(Σ)$. We show that under certain, very weak hypotheses, that if for a given $μ\in M(Σ)$ and all $A \in Σ$ the map $t \mapsto T_t μ(A)$ is in $H^\infty(\Bbb R)$, then it follows that the map $t \mapsto T_t μ$ is Bochner measurable. The proof is based upon the idea of the Analytic Radon Nikodým Property. Straightforward applications yield a new and simpler proof of Forelli's main result concerning analytic measures ({\it Analytic and quasi-invariant measures}, Acta Math., {\bf 118} (1967), 33--59).
We extend ideas of Garling to consider the so called Hardy martingales in a more general setting of H^p theory of compact abelian groups with ordered dual. As a consequence, we obtain a new proof of a result of Helson and Lowdenslager which generalizes Jensen's Inequality for H^1 functions.