A characterization of two weight norm inequality for Littlewood-Paley $g_{\lambda }^{\ast }$-function

Abstract

Let $n\ge 2$ and $g_{\lambda }^{\ast }$ be the well-known high dimensional Littlewood-Paley function which was defined and studied by E. M. Stein, \begin{align*} g_λ^{*}(f)(x) =\bigg(\iint_{\mathbb R^{n+1}_{+}} \Big(\frac{t}{t+|x-y|}\Big)^{nλ} |\nabla P_tf(y,t)|^2 \frac{dy dt}{t^{n-1}}\bigg)^{1/2}, \ \quad λ> 1, \end{align*} where $P_{t}f(y,t)=p_t\ast f(y)$, $p_t(y)=t^{-n}p(y/t)$ and $p(x)=(1+|x{|}^2{)}^{-(n+1)/2}$, $\nabla =(\frac{\partial }{\partial y_1},\dots ,\frac{\partial }{\partial y_n},\frac{\partial }{\partial t})$. In this paper, we give a characterization of two-weight norm inequality for $g_{\lambda }^{\ast }$-function. We show that, $\Vert g_{\lambda }^{\ast }(f\sigma ){\Vert }_{L^2(w)}\lesssim \Vert f{\Vert }_{L^2(\sigma )}$ if and only if the two-weight Muchenhoupt $A_2$ condition holds, and a testing condition holds : \begin{align*} \sup_{Q : cubes \ in \mathbb R^n} \frac{1}{σ(Q)} \int_{\mathbb R^n} \iint_{\widehat{Q}} \Big(\frac{t}{t+|x-y|}\Big)^{nλ}|\nabla P_t(\mathbf{1}_Q σ)(y,t)|^2 \frac{w dx dt}{t^{n-1}} dy < \infty, \end{align*} where $\hat{Q}$ is the Carleson box over $Q$ and $(w,\sigma )$ is a pair of weights. We actually prove this characterization for $g_{\lambda }^{\ast }$-function associated with more general fractional Poisson kernel $p^{\alpha }(x)=(1+|x{|}^2{)}^{-(n+\alpha )/2}$. Moreover, the corresponding results for intrinsic $g_{\lambda }^{\ast }$-function are also presented.

21 pages, to appear in Journal of Geometric Analysis

References in corpus (1)

• Two weight norm inequalities for the $g$ function