In this paper we are concerned with the properties of positivity, uncertainty principle and continuity in Lp spaces of a generalized spectrogram. In particular we study the connections of a generalized spectrogram, as a subclass of the Cohen class, with the Rihaczek and the Wigner representations. We also consider the behavior of the generalized spectrogram with respect to the positivity and th...

Let T be a Calderon-Zygmund operator, a classical result of Coifman, Rochberg and Weiss (see [7]) states that the commutator [b, T ] = T (bf)−bTf (where b ∈ BMO(Rn)) is bounded on Lp(Rn) for 1 < p < ∞; Chanillo (see [2]) proves a similar result when T is replaced by the fractional integral operator. However, it was observed that [b, T ] is not bounded, in general, from Hp(Rn) to Lp(Rn) for p ≤ ...

We establish two inequalities of Stein-Weiss type for the Riesz potential operator Iα,γ (B−Riesz potential operator) generated by the Laplace-Bessel differential operator ΔB in the weighted Lebesgue spaces Lp,|x|β ,γ . We obtain necessary and sufficient conditions on the parameters for the boundedness of Iα,γ from the spaces Lp,|x|β ,γ to Lq,|x|−λ ,γ , and from the spaces L1,|x|β ,γ to the weak...

By means of Muckenhoupt type conditions, we characterize the weights ω on C such that Bergman projection Fα2,ℓ=H(C)∩L2(C,e−α2|z|2ℓ), α>0, ℓ>1, is bounded Lp(C,e−αp2|z|2ℓω(z)), for 1<p<∞. We also obtain explicit representation integral formulas functions in weighted spaces Ap(ω)=H(C)∩Lp(ω). Finally, check validity so called Sarason conjecture about boundedness products certain Toeplitz operators...

The necessary and sufficient conditions are found for the weight function v, which provide the boundedness and compactness of the Riemann–Liouville operator Rα from Lp to L q v . The criteria are also established for the weight function w, which guarantee the boundedness and compactness of the Weyl operator Wα from L p w to Lq . In this paper, the necessary and sufficient conditions are found f...

X iv :m at h/ 05 12 40 7v 2 [ m at h. FA ] 1 8 Ja n 20 06 Notes on Matrix Valued Paraproducts Tao MEI 1 Abstract Denote by Mn the algebra of n×n matrices. We consider the dyadic paraproducts πb associated with Mn valued functions b, and show that the L(Mn) norm of b does not dominate ||πb||L2(l2n)→L2(l2n) uniformly over n. We also consider paraproducts associated with noncommutative martingales...

In this article, we will be concerned with questions related to the boundedness of the Riesz transform on manifolds. Since the seminal work of Coulhon and Duong [4], who gave sufficient conditions on the heat kernel so that the Riesz transform is bounded on Lp for 1 < p ≤ 2, several authors have investigated both necessary and sufficient conditions for the boundedness of the Riesz transform on ...