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Commutators of Littlewood-Paley sums   总被引:1,自引:0,他引:1  
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We define and investigate the Riesz transform associated with the differential operatorL λ f(θ)=−f"(θ)−2λ cot’θ. We prove that it can be defined as a principal value and that it is bounded onL P ([0, π],dm λ (θ)),dm λ(θ)=sin θdθ, for every 1<p<∞ and of weak type (1,1). The same boundedness properties hold for the maximal operator of the truncated operators. The speed of convergence of the truncated operators is measured in terms of the boundedness inL P (dm λ ), 1<p<∞, and weak type (1,1) of the oscillation and ρ-variation associated to them. Also, a multiplier theorem is proved to get the boundedness of the conjugate function studied by Muckenhoupt and Stein for 1<p<∞ as a corollary of the results for the Riesz transform. Moreover, we find a condition on the weightv which is necessary and sufficient for the existence of a weightu such that the Riesz transform is bounded fromL P (v dm λ ) intoL P (u dm λ ). The authors were partially supported by RTN Harmonic Analysis and Related Problems contract HPRN-CT-2001-00273-HARP. The first and fourth authors were supported in part by KBN grant 1-P93A 018 26. The second and third authors were partially supported by BFM grant 2002-04013-C02-02.  相似文献
3.
In this paper we present a new point of view to study the tent spaces introduced by Coifman, Meyer and Stein ([CMS1] and [CMS2]) by immersing them into vector-valued Lebesgue, Hardy and BMO spaces. This approach allows us to derive many of the known properties for tent spaces in a very simple manner. In fact most of the results are obtained as a consequence of similar results for those vector-valued spaces where they are immersed. The main tool we use to obtain such immersions and the applications to boundedness of operators, given in &4, is the vector-valued Calderón-Zygmund theory.  相似文献
4.
We derive Hölder regularity estimates for operators associated with a time-independent Schrödinger operator of the form $-\Delta +V$ . The results are obtained by checking a certain condition on the function $T1$ . Our general method applies to get regularity estimates for maximal operators and square functions of the heat and Poisson semigroups, for Laplace transform type multipliers and also for Riesz transforms and negative powers $(-\Delta +V)^{-\gamma /2}$ , all of them in a unified way.  相似文献
5.
The weighted Lebesgue spaces of initial data for which almost everywhere convergence of the heat equation holds was only very recently characterized. In this note we show that the same weighted space of initial data is optimal for the heat–diffusion parabolic equations involving the harmonic oscillator and the Ornstein–Uhlenbeck operator.  相似文献
6.
In this paper we prove the behaviour in weighted Lp spaces of the oscillation and variation of the Hilbert transform and the Riesz transform associated with the Hermite operator of dimension 1. We prove that this operator maps LP(R, w(x)dx) into itself when w is a weight in the Ap class for 1 〈 p 〈 ∞. For p = 1 we get weak type for the A1 class. Weighted estimated are also obtained in the extreme case p = ∞.  相似文献
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It is well known that the fundamental solution of
$${u_t}\left( {n,t} \right) = u\left( {n + 1,t} \right) - 2u\left( {n,t} \right) + u\left( {n - 1,t} \right),n \in \mathbb{Z},$$
with u(n, 0) = δ nm for every fixed m ∈ Z is given by u(n, t) = e −2t I n−m (2t), where I k (t) is the Bessel function of imaginary argument. In other words, the heat semigroup of the discrete Laplacian is described by the formal series W t f(n) = Σ m∈Z e −2t I n−m (2t)f(m). This formula allows us to analyze some operators associated with the discrete Laplacian using semigroup theory. In particular, we obtain the maximum principle for the discrete fractional Laplacian, weighted ℓ p (Z)-boundedness of conjugate harmonic functions, Riesz transforms and square functions of Littlewood-Paley. We also show that the Riesz transforms essentially coincide with the so-called discrete Hilbert transform defined by D. Hilbert at the beginning of the twentieth century. We also see that these Riesz transforms are limits of the conjugate harmonic functions. The results rely on a careful use of several properties of Bessel functions.
  相似文献
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We characterize Lusin type and cotype for a Banach space in terms of the L p -boundedness of Littlewood-Paley g-functions associated with the Hermite and Laguerre expansions.  相似文献
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