Svitlana Mayboroda, Alexander Volberg
Following a recent paper by X. Tolsa [JFA, 2008] we show that the finiteness of square function associated with the Riesz transforms with respect to Hausdorff measure $H^n$ ($n$ is interger) on a set $E$ implies that $E$ is rectifiable.
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The well-known curvature method initiated in works of Melnikov and Verdera is now commonly used to relate the $L^2(μ)$-boundedness of certain singular integral operators to the geometric properties of the support of measure $μ$, e.g. rectifiability. It can be applied however only if Menger curvature-like permutations, directly associated with the kernel of the operator, are non-negative. We give an example of an operator in the plane whose corresponding permutations change sign but the $L^2(μ)$-boundedness of the operator still implies that the support of $μ$ is rectifiable. To the best of our…
Let $E \subset \mathbb{C}$ be a Borel set such that $0<\mathcal{H}^1(E)<\infty$. David and Léger proved that the Cauchy kernel $1/z$ (and even its coordinate parts $\textrm{Re}\, z/|z|^2$ and $\textrm{Im}\, z/|z|^2$, $z\in \mathbb{C}\setminus\{0\}$) has the following property $(*)$: the $L^2(\mathcal{H}^1\lfloor E)$-boundedness of the corresponding singular integral operator implies the rectifiability of $E$. Recently Chousionis, Mateu, Prat and Tolsa extended this result to any kernel of the form $(\textrm{Re}\, z)^{2n-1}/|z|^{2n}$, $n\in \mathbb{N}$. In this paper, we prove that the property…
Recently, M. Badger and R. Schul proved that for a $1$-rectifiable Radon measure $μ$, the density weighted Jones' square function $$ J_{1}(x) = \mathop{\sum_{Q \in \mathcal{D}}}_{\ell(Q) \leq 1} β_{2,μ}^{2}(3Q)\frac{\ell(Q)}{μ(Q)} 1_{Q}(x) $$ is finite for $μ$-a.e. $x$. Answering a question of Badger-Schul, we show that the converse is not true. Given $ε> 0$, we construct a Radon probability measure on $[0,1]^{2} \subset \mathbb{R}^{2}$ with the properties that $J_{1}(x) \leq ε$ for all $x \in \operatorname{spt} μ$, but nevertheless the $1$-dimensional lower density of $μ$ vanishes almost ever…
Let $E \subset \C$ be a Borel set with finite length, that is, $0<\mathcal{H}^1 (E)<\infty$. By a theorem of David and Léger, the $L^2 (\mathcal{H}^1 \lfloor E)$-boundedness of the singular integral associated to the Cauchy kernel (or even to one of its coordinate parts $x / |z|^2,y / |z|^2,z=(x,y) \in \C$) implies that $E$ is rectifiable. We extend this result to any kernel of the form $x^{2n-1} /|z|^{2n}, z=(x,y) \in \C,n \in \mathbb{N}$. We thus provide the first non-trivial examples of operators not directly related with the Cauchy transform whose $L^2$-boundedness implies rectifiability.
We prove that if $μ$ is a d-dimensional Ahlfors-David regular measure in $\R^{d+1}$, then the boundedness of the $d$-dimensional Riesz transform in $L^2(μ)$ implies that the non-BAUP David-Semmes cells form a Carleson family. Combined with earlier results of David and Semmes, this yields the uniform rectifiability of $μ$.
Let $A(\cdot)$ be an $(n+1)\times (n+1)$ uniformly elliptic matrix with Hölder continuous real coefficients and let $\mathcal E_A(x,y)$ be the fundamental solution of the PDE $\mathrm{div} A(\cdot) \nabla u =0$ in $\mathbb R^{n+1}$. Let $μ$ be a compactly supported $n$-AD-regular measure in $\mathbb R^{n+1}$ and consider the associated operator $$T_μf(x) = \int \nabla_x\mathcal E_A(x,y)\,f(y)\,dμ(y).$$ We show that if $T_μ$ is bounded in $L^2(μ)$, then $μ$ is uniformly $n$-rectifiable. This extends the solution of the codimension $1$ David-Semmes problem for the Riesz transform to the gradient…
In this paper it is shown that an Ahlfors-David $n$-dimensional measure $μ$ on $\mathbb{R}^d$ is uniformly $n$-rectifiable if and only if for any ball $B(x_0,R)$ centered at $\operatorname{supp}(μ)$, $$ \int_0^R \int_{x\in B(x_0,R)} \left|\frac{μ(B(x,r))}{r^n} - \frac{μ(B(x,2r))}{(2r)^n} \right|^2\,dμ(x)\,\frac{dr}r \leq c\, R^n.$$ Other characterizations of uniform $n$-rectifiability in terms of smoother square functions are also obtained.
Square Functions Controlling Smoothness and Higher-Order Rectifiability
该研究针对0<α<2的BMO-Sobolev空间I_α(BMO)，分别用衡量常数、线性函数多尺度逼近的平方函数给出不同α区间下的新刻画，推进了相关空间的特征研究。
Interactions between quantitative rectifiability, singular integrals, and boundary value problems for harmonic functions
该论文围绕定量可求长性展开，回顾其与可求长性刻画、里斯变换L²有界性的联系及应用，还探讨了其在粗糙区域中拉普拉斯方程相关问题的L^p可解性方面的关键作用。
We consider the Calderón-Zygmund kernels $K_ {α,n}(x)=(x_i^{2n-1}/|x|^{2n-1+α})_{i=1}^d$ in $\mathbb{R}^n$ for $0<α\leq 1$ and $n\in\mathbb{N}$. We show that, on the plane, for $0<α<1$, the capacity associated to the kernels $K_{α,n}$ is comparable to the Riesz capacity $C_{\frac23(2-α),\frac 3 2}$ of non-linear potential theory. As consequences we deduce the semiadditivity and bi-Lipschitz invariance of this capacity. Furthermore we show that for any Borel set $E\subset\mathbb{R}^n$ with finite length the $L^2(\mathcal{H}^1 \lfloor E)$-boundedness of the singular integral associated to $K_{1,…
We show that a Radon measure $μ$ in $\mathbb R^d$ which is absolutely continuous with respect to the $n$-dimensional Hausdorff measure $H^n$ is $n$-rectifiable if the so called Jones' square function is finite $μ$-almost everywhere. The converse of this result is proven in a companion paper by the second author, and hence these two results give a classification of all $n$-rectifiable measures which are absolutely continuous with respect to $H^{n}$. Further, in this paper we also investigate the relationship between the Jones' square function and the so called Menger curvature of a measure with…
For a Radon measure $μ$ on $\mathbb{R}^d$, define $C^n_μ(x, t)= \ (\frac{1}{t^n} \ |\int_{B(x,t)} \frac{x-y}{t} \, dμ(y)\ | \ )$. This coefficient quantifies how symmetric the measure $μ$ is by comparing the center of mass at a given scale and location to the actual center of the ball. We show that if $μ$ is $n$-rectifiable, then $ \int_0^\infty |C^n_μ(x,t)|^2 \frac{dt}{t} < \infty \, \, μ\mbox{-almost everywhere}. $ Together with a previous result of Mayboroda and Volberg, where they showed that the converse holds true, this gives a characterisation of $n$-rectifiability. To prove our main re…
In this paper it is shown that if $μ$ is a finite Radon measure in $\mathbb R^d$ which is $n$-rectifiable and $1\leq p\leq 2$, then $$\int_0^\infty β_{μ,p}^n(x,r)^2\,\frac{dr}r<\infty \quad {for $μ$-a.e. $x\in\mathbb R^d$,}$$ where $$β_{μ,p}^n(x,r) = \inf_L (\frac1{r^n} \int_{\bar B(x,r)} (\frac{\mathrm dist(y,L)}{r})^p\,dμ(y))^{1/p},$$ with the infimum taken over all the $n$-planes $L\subset \mathbb R^d$. The $β_{μ,p}^n$ coefficients are the same as the ones considered by David and Semmes in the setting of the so called uniform $n$-rectifiability. An analogous necessary condition for $n$-rect…
Let $E$ be a set in $\mathbb R^d$ with finite $n$-dimensional Hausdorff measure $H^n$ such that $\liminf_{r\to0}r^{-n} H^n(B(x,r)\cap E)>0$ for $H^n$-a.e. $x\in E$. In this paper it is shown that $E$ is $n$-rectifiable if and only if $$\int_0^1 \left|\frac{H^n(B(x,r)\cap E)}{r^n} - \frac{H^n(B(x,2r)\cap E)}{(2r)^n}\right|^2\,\frac{dr}r < \infty$$ for $H^n$-a.e. $x\in E$; and also if and only if $$ \lim_{r\to0}\left(\frac{H^n(B(x,r)\cap E)}{r^n} - \frac{H^n(B(x,2r)\cap E)}{(2r)^n}\right) = 0$$ for $H^n$-a.e. $x\in E$. Other more general results involving Radon measures are also proved.
We say a measure is $C^{1,α}$ $d$-rectifiable if there is a countable union of $C^{1,α}$ $d$-surfaces whose complement has measure zero. We provide sufficient conditions for a Radon measure in $\mathbb{R}^n$ to be $C^{1,α}$ $d$-rectifiable, with $α\in (0,1]$. The conditions involve a Bishop-Jones type square function and all statements are quantitative in that the $C^{1,α}$ constants depend on such a function. Along the way we also give sufficient conditions for $C^{1,α}$ parametrizations for Reifenberg flat sets in terms of the same square function. Key tools for the proof come from David and…
In some former works of Azzam and Tolsa it was shown that $n$-rectifiability can be characterized in terms of a square function involving the David-Semmes $β_2$ coefficients. In the present paper we construct some counterexamples which show that a similar characterization does not hold for the $β_p$ coefficients with $p\neq2$. This is in strong contrast with what happens in the case of uniform $n$-rectifiability. In the second part of this paper we provide an alternative argument for a recent result of Edelen, Naber and Valtorta about the $n$-rectifiability of measures with bounded lower $n$-d…
In this paper we prove $L^p$ estimates for Stein's square functions associated to Fourier-Bessel expansions. Furthermore we prove transference results for square functions from Fourier-Bessel series to Hankel transforms. Actually, these are transference results for vector-valued multipliers from discrete to continuous in the Bessel setting. As a consequence, we deduce the sharpness of the range of $p$ for the $L^p$-boundedness of Fourier-Bessel Stein's square functions from the corresponding property for Hankel-Stein square functions. Finally, we deduce $L^p$ estimates for Fourier-Bessel multi…
Let $Ω\subset\mathbb{R}^{n+1}$, $n\geq2$, be an open set with Ahlfors-David regular boundary that satisfies the corkscrew condition. We consider a uniformly elliptic operator $L$ in divergence form associated with a matrix $A$ with real, merely bounded and possibly non-symmetric coefficients, which are also locally Lipschitz and satisfy suitable Carleson type estimates. In this paper we show that if $L^*$ is the operator in divergence form associated with the transpose matrix of $A$, then $\partialΩ$ is uniformly $n$-rectifiable if and only if every bounded solution of $Lu=0$ and every bounded…
Let $Ω\subset\mathbb R^{n+1}$, $n\geq1$, be a corkscrew domain with Ahlfors-David regular boundary. In this paper we prove that $\partialΩ$ is uniformly $n$-rectifiable if every bounded harmonic function on $Ω$ is $\varepsilon$-approximable or if every bounded harmonic function on $Ω$ satisfies a suitable square-function Carleson measure estimate. In particular, this applies to the case when $Ω=\mathbb R^{n+1}\setminus E$ and $E$ is Ahlfors-David regular. Our results solve a conjecture posed by Hofmann, Martell, and Mayboroda in a recent work where they proved the converse statements. Here we …
Square Functions and Rectifiability under Monotone Transformations of the Density
本文证明密度经区间上双Lipschitz函数复合后，原关于n-AD正则测度一致n-可求长性的平方函数Carleson条件刻画仍成立，还推广了光滑平方函数等情形的相关结论。
This paper is devoted to the proof of boundedness of bilinear smooth square functions. Moreover, we deduce boundedness of some bilinear pseudo-differential operators associated with symbols belonging to a subclass of $BS^0_{0,0}$.
In this paper, by using the atomic decomposition theorem for weighted weak Hardy spaces, we will show the boundedness properties of intrinsic square functions including the Lusin area integral, Littlewood-Paley $g$-function and $g^*_λ$-function on these spaces.
We consider a class of bi-parameter kernels and related square functions in the upper half-space, and give an efficient proof of a boundedness criterion for them. The proof uses modern probabilistic averaging methods and is based on controlling double Whitney averages over good cubes.
The multilinear Littlewood-Paley square operators and their commutators on weighted Morrey spaces
本文证明了多重线性Littlewood-Paley平方算子及其交换子在加权Morrey空间上的有界性，并给出了相关g-函数和Marcinkiewicz积分交换子的推论。
We characterize geometric properties of Banach spaces in terms of boundedness of square functions associated to general Schrodinger operators of the form $L=-Δ+V$, where the nonnegative potential $V$ satisfies a reverse Holder inequality. The main idea is to sharpen the well known localization method introduced by Z. Shen. Our results can be regarded as alternative proofs of the boundedness in $H^1$, $L^p$ and $BMO$ of classical $L$-square functions.
In this paper, we characterize the rectifiability (both uniform and not) of an Ahlfors regular set, E, of arbitrary co-dimension by the behavior of a regularized distance function in the complement of that set. In particular, we establish a certain version of the Riesz transform characterization of rectifiability for lower-dimensional sets. We also uncover a special situation in which the regularized distance is itself a solution to a degenerate elliptic operator in the complement of E. This allows us to precisely compute the harmonic measure of those sets associated to this degenerate operato…
In this paper, we will study the strong type and weak type estimates of intrinsic square functions including the Lusin area integral, Littlewood-Paley $g$-function and $g^*_λ$-function on the generalized Morrey spaces $L^{p,Φ}$ for $1\le p<\infty$, where $Φ$ is a growth function on $(0,\infty)$ satisfying the doubling condition. The boundedness of the commutators generated by $BMO(\mathbb R^n)$ functions and intrinsic square functions is also obtained.
In this paper, we will obtain the strong type and weak type estimates for vector-valued analogues of intrinsic square functions in the weighted Morrey spaces $L^{p,κ}(w)$ when $1\leq p<\infty$, $0<κ<1$, and in the generalized Morrey spaces $L^{p,Φ}$ for $1\le p<\infty$, where $Φ$ is a growth function on $(0,\infty)$ satisfying the doubling condition.
In this paper, we will obtain the strong type and weak type estimates of intrinsic square functions including the Lusin area integral, Littlewood-Paley $g$-function and $g^*_λ$-function on the weighted Herz spaces $\dot K^{α,p}_q(w_1,w_2)$ ($K^{α,p}_q(w_1,w_2)$) with general weights.
On the Boundedness in $H^{1/4}$ of the Maximal Square Function Associated with the Schroedinger Equation
线性薛定谔方程的一个长期存在的猜想指出，在索伯列夫空间的意义下，$L^2$中的1/4导数足以使该方程的解在任何维度上几乎处处收敛到初始数据。这是唯一已知的是真实的一维工作的Carleson。在本文中，我们证明了该猜想是正确的球平均。更精确地说，我们证明了Sobolev类$H^{1/4}(R^n)$上相关极大平方函数在任意维数n上的$L^2$有界性.
We continue the study of local $Tb$ theorems for square functions defined in the upper half-space $(\mathbb{R}^{n+1}_+, μ\times dt/t)$. Here $μ$ is allowed to be a non-homogeneous measure in $\mathbb{R}^n$. In this paper we prove a boundedness result assuming local $L^q$ type testing conditions in the difficult range $q \in (1,2)$. Our theorem is a non-homogeneous version of a result of S. Hofmann valid for the Lebesgue measure. It is also an extension of the recent results of M. Lacey and the first named author where non-homogeneous local $L^2$ testing conditions have been considered.
In this paper we establish $L^p(\mathbb{R}^d,γ_\infty)$-boundedness properties for square functions involving time and spatial derivatives of Ornstein-Uhlenbeck semigroups. Here $γ_\infty$ denotes the invariant measure. In order to prove the strong type results for $1<p<\infty$ we use $R$-boundedness. The weak type (1,1) property is established by studying separately global and local operators defined for the square Littlewood-Paley functions. By the way we prove $L^p(\mathbb{R}^d,γ_\infty)$-boundedness properties for maximal and variation operators for Ornstein-Uhlenbeck semigroups.
On the boundedness for the bilinear quadratic functional given by arbitrary strips
研究由任意不相交条带定义的光滑双线性二次泛函的有界性，该泛函结合了线性Rubio de Francia平方函数与双线性Hilbert变换的调制不变奇异结构。
The Usual Square Function on Weakly Flat Sets
研究平面上Cauchy单层核的通常平方函数估计，证明满足该估计和弱平坦条件的有限Radon测度是可求长的，并给出支撑在局部双侧NTA曲线或拟圆上的可求长性推论。
We continue developing the theory of conical and vertical square functions on $R^{n}$, where $μ$ is a power bounded measure, possibly non-doubling. We provide new boundedness criteria and construct various counterexamples. First, we prove a general local $Tb$ theorem with tent space $T^{2,\infty}$ type testing conditions to characterise the $L^{2}$ boundedness. Second, we completely answer the question, whether the boundedness of our operators on $L^{2}$ implies boundedness on other $L^{p}$ spaces, including the endpoints. For the conical square function, the answers are generally affirmative,…
Two-weight estimates for the square function and $t$-Haar multipliers
本文研究了权三元组$(u,v,w)$下二进加权平方函数$S_w$与$t$-Haar乘子从$L^2(u)$到$L^2(v)$的有界性，给出了两者的充要条件并建立了基于平方函数有界性的刻画。
Boundedness of a class of multilinear operators and their iterated commutators on Morrey-Banach function spaces
本文在广义Morrey-Banach函数空间框架下，针对含多线性ω-Calderón-Zygmund算子等的算子类，通过逐点稀疏控制假设或Wᵣ性质建立其及交换子的有界性，并将迭代交换子有界性推广到Morrey-Lorentz空间和变指数Morrey空间。
We characterize the boundedness of square functions in the upper half-space with general measures. The short proof is based on an averaging identity over good Whitney regions.
In this paper we introduce Stein's square function associated with bilinear Bochner-Riesz means and investigate its $L^p$ boundedness properties. Further, we discuss several applications of the square function in the context of bilinear multipliers. In particular, we obtain results for maximal function associated with generalised bilinear Bochner-Riesz means. This extends the results proved in~\cite{JS}. Another application concerns the $L^p$ estimates for bilinear fractional Schrödinger multipliers. Finally, we improve upon a result of Grafakos, He and Honzik~\cite{GHH} in the context of bili…
A local Tb theorem is an L^2 boundedness criterion by which the question of the global behavior of an operator is reduced to its local behavior, acting on a family of test functions b_Q indexed by the dyadic cubes. We present several versions of such results, in particular, treating square function operators whose kernels do not satisfy the standard Littlewood-Paley pointwise estimates. As an application of one version of the local Tb theorem, we show how the solvability of the Kato problem (which was implicitly based on local Tb theory) may be deduced from this general criterion. We also pres…
Weak Type Estimates for Square Functions of Dunkl Heat Flows
本文通过积分型Dunkl热核估计和Caldrón--Zygmund分解，证明了Dunkl热流的Littlewood--Paley--Stein平方函数的弱(1,1)有界性，延续了先前关于该函数无维L^p有界性的研究。
UMD Banach spaces and square functions associated with heat semigroups for Schrödinger and Laguerre operators
本文定义了与 Schrödinger 和 Laguerre 算子热半群相关联的 UMD Banach 空间取值平方函数，利用 γ-radonifying 算子将其经典 L^p-有界性扩展至 Banach 取值设定，并证明该性质可刻画 Banach 空间的 UMD 性质。
In this paper, we will study the boundedness of intrinsic square functions on the weighted Hardy spaces $H^p(w)$ for $0<p<1$, where $w$ is a Muckenhoupt's weight function. We will also give some intrinsic square function characterizations of weighted Hardy spaces $H^p(w)$ for $0<p<1$.
The Interplay of Shifted Square and Maximal Function Estimates in the Context of Multilinear Fourier Multipliers
本文通过移位正方形和最大函数的结合，改进了多线性傅里叶乘子的有界性定理，并应用于奇异积分在Orlicz空间中的有界性研究。
UMD-valued square functions associated with Bessel operators in Hardy and BMO spaces
本文研究 Bessel 背景下 Banach 取值 Hardy 和 BMO 空间，利用分数阶导数定义平方函数，证明了 UMD 空间中涉及 $γ$-radonifying 算子的等价范数，并基于 g-函数的有界性刻画了 UMD Banach 空间。
In this paper, we will study the boundedness properties of intrinsic square functions including the Lusin area integral, Littlewood-Paley $g$-function and $g^*_λ$-function on the weighted Morrey spaces $L^{p,κ}(w)$ for $1<p<\infty$ and $0<κ<1$. The corresponding commutators generated by $BMO(\mathbb R^n)$ functions and intrinsic square functions are also discussed.
Let $P(D)$ be the Laplacian $Δ,$ or the wave operator $\square$. The following type of Carleman estimate is known to be true on a certain range of $p,q$: \[ \|e^{v\cdot x}u\|_{L^q(\mathbb{R}^d)} \le C\|e^{v\cdot x}P(D)u\|_{L^p(\mathbb{R}^d)} \] with $C$ independent of $v\in \mathbb{R}^d$. The estimates are consequences of the uniform Sobolev type estimates for second order differential operators due to Kenig-Ruiz-Sogge \cite{KRS} and Jeong-Kwon-Lee \cite{JKL}. The range of $p,q$ for which the uniform Sobolev type estimates hold was completely characterized for the second order differential ope…
New index transforms, involving the square of Bessel functions of the first kind as the kernel are considered. Mapping properties such as the boundedness and invertibility are investigated for these operators in the Lebesgue spaces. Inversion theorems are proved. As an interesting application, a solution to the initial value problem for the third order partial differential equation, involving the Laplacian, is obtained.
In this paper we consider square functions (also called Littlewood-Paley g-functions) associated to Hankel convolutions acting on functions in the Bochner-Lebesgue space $L^p((0,\infty),B)$, where $B$ is a UMD Banach space. As special cases we study square functions defined by fractional derivatives of the Poisson semigroup for the Bessel operator $Δ_λ=-x^{-λ}\frac{d}{dx}x^{2λ}\frac{d}{dx}x^{-λ}$, $λ>0$. We characterize the UMD property for a Banach space $B$ by using $L^p((0,\infty),B)$-boundedness properties of g-functions defined by Bessel-Poisson semigroups. As a by product we prove that t…
Estimates for maximal Fourier multiplier operators on $\Bbb R^2$ via square functions
本文通过平方函数估计，推导出Bochner-Riesz型傅里叶乘子在R²上的最大函数L^p有界性，扩展了Carbery 1983年的结果。
We show $\ell^p\big(\mathbb Z^d\big)$ boundedness, for $p\in(1, \infty)$, of discrete singular integrals of Radon type with the aid of appropriate square function estimates, which can be thought as a discrete counterpart of the Littlewood--Paley theory. It is a very powerful approach which allows us to proceed as in the continuous case.
$L^{p}$ estimates for multilinear maximal Bochner--Riesz means and square function
本文研究多线性极大Bochner–Riesz平均及其平方函数的$L^{p}$有界性，借鉴Jotsaroop和Shrivastava关于双线性Bochner–Riesz平均极大估计的方法完成证明。
In this paper, we establish sufficient conditions for a singular integral $T$ to be bounded from certain Hardy spaces $H^p_L$ to Lebesgue spaces $L^p$, $0< p \le 1$, and for the commutator of $T$ and a BMO function to be weak-type bounded on Hardy space $H_L^1$. We then show that our sufficient conditions are applicable to the following cases: (i) $T$ is the Riesz transform or a square function associated with the Laplace-Beltrami operator on a doubling Riemannian manifold, (ii) $T$ is the Riesz transform associated with the magnetic Schrödinger operator on an Euclidean space, and (iii) $T = g…
In this paper, we obtain some boundedness of the following general multilinear square functions $T$ with non-smooth kernels, which extend some known results significantly. $$ T(\vec{f})(x)=\big( \int_{0}^\infty \big|\int_{(\mathbb{R}^n)^m}K_v(x,y_1,\dots,y_m) \prod_{j=1}^mf_{j}(y_j)dy_1,\dots,dy_m\big|^2\frac{dv}{v}\big)^{\frac 12}. $$ The corresponding multilinear maximal square function $T^*$ was also introduced and weighted strong and weak type estimates for $T^*$ were given.
The aim of this paper is to study the boundedness of different conical square functions that arise naturally from second order divergence form degenerate elliptic operators. More precisely, let $L_w=w^{-1}\,{\rm div}(w\,A\,\nabla)$ where $w\in A_2$ and $A$ is an $n\times n$ bounded, complex-valued, uniformly elliptic matrix. D. Cruz-Uribe and C. Rios solved the $L^2(w)$-Kato square root problem obtaining that $\sqrt{L_w}$ is equivalent to the gradient on $L^2(w)$. The same authors in collaboration with the second named author of this paper studied the $L^p(w)$-boundedness of operators that are…
Weighted Weak Type estimates for non-integral Square Functions
本文针对非积分平方函数在临界情形 $p=2$ 下，利用 Gehring 引理的定量版本解耦权函数作用，建立了以 $A_p$ 和逆 Hölder 常数表示的定量加权弱型估计，并可推广至其他有界性范围内的 $p$ 值。
Square functions in the Hermite setting for functions with values in UMD spaces
本文利用 Hermite 背景下的 Littlewood-Paley $g$-函数和 $γ$-radonifying 算子，刻画了取值于 UMD Banach 空间的 Lebesgue Bochner 空间，并通过该 $g$-函数的有界性反向刻画了 UMD Banach 空间。
The bilinear cone multiplier on $\mathbb{R}^2\times \mathbb{R}^2$
本文研究了二维空间上的双线性锥乘法子，通过将双线性算子分解为与线性锥乘法子及其变体相关的平方函数，并利用合适的强极大值估计和几何方法，得到了双线性锥乘法子的$ L^p $有界性。
In this paper, the boundedness properties of commutators generated by $b$ and intrinsic square functions in the endpoint case are discussed, where $b\in BMO(\mathbb R^n)$. We first establish the weighted weak $L\log L$-type estimates for these commutator operators. Furthermore, we will prove endpoint estimates of commutators generated by $BMO(\mathbb R^n)$functions and intrinsic square functions in the weighted Morrey spaces $L^{1,κ}(w)$ for $0<κ<1$ and $w\in A_1$, and in the generalized Morrey spaces $L^{1,Θ}$, where $Θ$ is a growth function on $(0,+\infty)$ satisfying the doubling condition.
We consider the square function (known as Stein's square function) estimate associated with the Bochner-Riesz means. The previously known range of sharp estimate is improved. Our results are based on vector valued extensions of Bennett-Carbery-Tao's multilinear (adjoint) restriction estimate and adaption of induction argument due to Bourgain-Guth. Unlike the previous work by Bourgain-Guth on $L^p$ boundedness of Bochner-Riesz means in which oscillatory operators associated to the kernel had been studied, we take more direct approach by working on the Fourier transform side. This enables us to …
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