9,438 research outputs found

    A note on weighted bounds for rough singular integrals

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    We show that the L2(w)L^2(w) operator norm of the composition M ⁣TΩM\!\circ T_{\Omega}, where MM is the maximal operator and TΩT_{\Omega} is a rough homogeneous singular integral with angular part ΩL(Sn1)\Omega\in L^{\infty}(S^{n-1}), depends quadratically on [w]A2[w]_{A_2}, and this dependence is sharp

    Sharp weighted norm inequalities for Littlewood-Paley operators and singular integrals

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    We prove sharp Lp(w)L^p(w) norm inequalities for the intrinsic square function (introduced recently by M. Wilson) in terms of the ApA_p characteristic of ww for all 1<p<1<p<\infty. This implies the same sharp inequalities for the classical Lusin area integral S(f)S(f), the Littlewood-Paley gg-function, and their continuous analogs SψS_{\psi} and gψg_{\psi}. Also, as a corollary, we obtain sharp weighted inequalities for any convolution Calder\'on-Zygmund operator for all 1<p3/21<p\le 3/2 and 3p<3\le p<\infty, and for its maximal truncations for 3p<3\le p<\infty

    On weighted norm inequalities for the Carleson and Walsh-Carleson operators

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    We prove Lp(w)L^p(w) bounds for the Carleson operator C{\mathcal C}, its lacunary version Clac\mathcal C_{lac}, and its analogue for the Walsh series \W in terms of the AqA_q constants [w]Aq[w]_{A_q} for 1qp1\le q\le p. In particular, we show that, exactly as for the Hilbert transform, CLp(w)\|{\mathcal C}\|_{L^p(w)} is bounded linearly by [w]Aq[w]_{A_q} for 1q<p1\le q<p. We also obtain Lp(w)L^p(w) bounds in terms of [w]Ap[w]_{A_p}, whose sharpness is related to certain conjectures (for instance, of Konyagin \cite{K2}) on pointwise convergence of Fourier series for functions near L1L^1. Our approach works in the general context of maximally modulated Calder\'on-Zygmund operators.Comment: A major revision of arXiv: 1310.3352. In particular, the main result is proved under a different assumption, and applications to the lacunary Carleson operator and to the Walsh-Carleson operator are give
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