In this paper, optimal $L^p-L^q$ estimates are obtained for operators which average functions over polynomial submanifolds, generalizing the $k$-plane transform. An important advance over previous work is that full $L^p-L^q$ estimates are obtained by methods which have traditionally yielded only restricted weak-type estimates. In the process, one is lead to make coercivity estimates for certain functionals on $L^p$ for $p < 1$.
We present a new family of sharp examples for the Szemerédi-Trotter theorem. These are the first examples not based on a rectangular lattice. We also include an application to the discrete inverse Loomis-Whitney problem.
Sharp estimates for the Fourier transform of surface-carried measures and maximal operators associated with hypersurfaces in $\mathbb{R}^4$ with vanishing Gaussian curvature
V. I. Romanovsky Institute of Mathematics, Uzbekistan Academy of Sciences(乌兹别克斯坦科学院 V.I. 罗曼诺夫斯基数学研究所);Institut für Analysis und Numerik, Fachbereich Mathematik und Informatik der Universität Münster(明斯特大学数学与信息学院分析与数值研究所)
We derive bilateral estimates for the constants appearing in the Fourier transform restricted theorems on the Euclidean sphere for the ordinary and especially radial functions belonging to the Lebesgue-Riesz spaces as well as belonging to the Grand Lebesgue Spaces. We obtain an exact estimate for the norm of the restriction Fourier transform operator acting on the radial functions.
This paper may be viewed as a companion paper to [G1]. In that paper, $L^2$ Sobolev estimates derived from a Newton polyhedron-based resolution of singularities method are combined with interpolation arguments to prove $L^p$ to $L^q_s$ estimates, some sharp up to endpoints, for translation invariant Radon transforms over hypersurfaces and related operators. Here $q \geq p$ and $s$ can be positive, negative, or zero. In this paper, we instead use $L^2$ Sobolev estimates derived from the resolution of singularities methods of [G2] and combine with analogous interpolation arguments, again resulti…
On Mattila's intersection problem in the plane: sharp dimension and positive measure of rotated difference sets
Institute of Mathematics and Interdisciplinary Sciences, Xidian University(西安电子科技大学数学与交叉科学研究院);National Taiwan University(台湾大学);VNU University of Science, Hanoi, Vietnam(越南河内国立大学科学大学)
This is an expository paper. We give proofs of some results of M. Christ (1984) and S. W. Drury (1984) for $k$-plane transforms. Also, we give proofs for some related results including that for the existence of invariant measures on certain homogeneous manifolds of Lie groups.
Sharp estimates for the commutators of the Hilbert, Riesz transforms and the Beurling-Ahlfors operator on weighted Lebesgue spaces
我们证明了Hilbert变换、Riesz变换和Beurling变换的算子在加权Lebesgue空间L2(w)上的范数与BMO函数b的A2-特征相关,而不是已知的算子本身的线性相关.我们知道,这类交换子的算子范数可以由交换子的范数通过适当的Haar移位算子控制,并证明了这类交换子的估计.对于与希尔伯特变换对应的移位算子,我们使用贝尔曼函数方法,然而现在有一类Haar移位算子的一般定理,可以用来推导类似的结果。我们利用这个一般定理得到了里斯变换和Beurling-Ahlfors算子的相应结果。然后我们可以外推到Lp(w),结果对于1 < p < 1是尖锐的。
We study integral transforms mapping a function on the Euclidean plane to the family of its integration on plane curves, that is, a function of plane curves. The plane curves we consider in the present paper are given by the graphs of functions with a fixed axis of the independent variable, and are imposed some symmetry with respect to the axes. These transforms contain the parabolic Radon transform and the hyperbolic Radon transform arising from seismology. We prove the inversion formulas for these transforms under some vanishing and symmetry conditions of functions.
Though Adams and Hardy-Adams inequalities can be extended to general symmetric spaces of noncompact type fairly straightforwardly by following closely the systematic approach developed in our early works on real and complex hyperbolic spaces, higher order Poincaré-Sobolev and Hardy-Sobolev-Maz'ya inequalities are more difficult to establish. The main purpose of this goal is to establish the Poincaré-Sobolev and Hardy-Sobolev-Maz'ya inequalities on quaternionic hyperbolic spaces and the Cayley hyperbolic plane. A crucial part of our work is to establish appropriate factorization theorems on the…
We study the basic properties of d-plane transform on the Euclidean space as a Fourier integral operator, and its application to the microlocal analysis of streaking artifacts in its filtered back-projection. The d-plane transform is defined by integrals of functions on the n-dimensional Euclidean space over all the d-dimensional planes, where 0<d<n. This maps functions on the Euclidean space to those on the affine Grassmannian G(d,n). This is said to be X-ray transform if d=1 and Radon transform if d=n-1. When n=2 the X-ray transform is thought to be measurements of CT scanners. In this paper…
Following the ideas of A. Lerner, F. Nazarov, S. Ombrosi from [12] we prove that there is a sequence of weights $w\in A^d_1$ such that $[w]^d_{A_1}\to \infty$, and martingale transforms $T$ such that with an absolute positive $c$ $\|T: L^1(w) \to L^{1, \infty}(w)\| \ge c [w]^d_{A_1}\log [w]^d_{A_1}$. We also show the existence of the sequence of weights (now in $A_2$) such that $[w]^d_{A_2}\to \infty$, and such that the following holds: $[w]_{A_2^d}\asymp \|M^d\|_{w^{-1}}^2$; $\|S_{w}: L^{2} (w) \to L^2(w^{-1})\| \ge c\, \|M^d\|_{w^{-1}}\sqrt{\log \|M^d\|_{w^{-1}}}$; $\|S_{w}: L^{2,1} (w) \to …