José García-Cuerva

Wavelet characterization of weighted spaces

We give a characterization of weighted Hardy spaces Hp(w), valid for a rather large collection of wavelets, 0 <p ≤ 1,and weights w in the Muckenhoupt class A∞We improve the previously known results and adopt a systematic point of view based upon the theory of vector-valued Calderón-Zygmund operators. Some consequences of this characterization are also given, like the criterion for a wavelet to give an unconditional basis and a criterion for membership into the space from the size of the wavelet coefficients.

Higher-order Riesz operators for the Ornstein-Uhlenbeck semigroup

We prove that the second-order Riesz transforms associated to the Ornstein–Uhlenbeck semigroup are weak type (1,1) with respect to the Gaussian measure in finite dimension. We also show that they are given by a principal value integral plus a constant multiple of the identity. For the Riesz transforms of order three or higher, we present a counterexample showing that the weak type (1,1) estimate fails.

Maximal operators for the holomorphic Ornstein-Uhlenbeck semigroup

For each p in [1, ∞) let Ep denote the closure of the region of holomorphy of the Ornstein-Uhlenbeck semigroup {Ht : t> 0} on L p with respect to the Gaussian measure. We prove sharp weak type and strong type estimates for the maximal operator f �→ H ∗ f = sup{|Hzf | : z ∈ Ep} and for a class of related operators. As a consequence of our methods, we give a new and simpler proof of the weak type 1 estimate for the maximal operator associated to the Mehler kernel.

On the existence of principal values for the Cauchy integral on weighted Lebesgue spaces for non-doubling measures.

AbstractLet T be a Calderón-Zygmund operator in a “non-homogeneous” space (

Vector-valued Hausdorff–Young inequality on compact groups

\mathbb{X}

Studies in Advanced Mathematics

, d, μ), where, in particular, the measure μ may be non-doubling. Much of the classical theory of singular integrals has been recently extended to this context by F. Nazarov, S. Treil, and A. Volberg and, independently by X. Tolsa. In the present work we study some weighted inequalities for T*, which is the supremum of the truncated operators associated with T. Specifically, for1<p<∞, we obtain sufficient conditions for the weight in one side, which guarantee that another weight exists in the other side, so that the corresponding Lp weighted inequality holds for T*. The main tool to deal with this problem is the theory of vector-valued inequalities for T* and some related operators. We discuss it first by showing how these operators are connected to the general theory of vector-valued Calderón-Zygmund operators in non-homogeneous spaces, developed in our previous paper [6]. For the Cauchy integral operator C, which is the main example, we apply the two-weight inequalities for C* to characterize the existence of principal values for functions in weighted Lp.

Boundedness properties of fractional integral operators associated to non-doubling measures

Sharp Fourier type and cotype of Lebesgue spaces and Schatten classes with respect to an arbitrary compact semisimple Lie group are investigated. In the process, a local variant of the Hausdorff-Young inequality on such groups is given.

Hardy Spaces and Beurling Algebras

The main purpose of this paper is to study the validity of the Hausdorff?Young inequality for vector-valued functions defined on a non-commutative compact group. As we explain in the introduction, the natural context for this research is that of operator spaces. This leads us to formulate a whole new theory of Fourier type and cotype for the category of operator spaces. The present paper is the first step in this program, where the basic theory is presented, the main examples are analyzed and some important questions are posed.