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A series expansion for Heckman-Opdam hypergeometric functions $\varphi_\lambda$ is obtained for all $\lambda \in \mathfrak a^*_{\mathbb C}.$ As a consequence, estimates for $\varphi_\lambda$ away from the walls of a Weyl chamber are…

Representation Theory · Mathematics 2015-11-16 E. K. Narayanan , A. Pasquale , S. Pusti

This work studies the Fourier transform of the characteristic function of planar convex bodies averaged over affine transformations. We establish lower and upper bounds on the latter quantities in terms of the geometric properties of the…

Number Theory · Mathematics 2025-07-02 Thomas Beretti

Covering numbers are a powerful tool used in the development of approximation algorithms, randomized dimension reduction methods, smoothed complexity analysis, and others. In this paper we prove upper bounds on the covering number of…

Algebraic Geometry · Mathematics 2025-06-09 Yifan Zhang , Joe Kileel

We prove Fourier restriction estimates by means of the polynomial partitioning method for compact subsets of any sufficiently smooth hyperbolic hypersurface in threedimensional euclidean space. Our approach exploits in a crucial way the…

Classical Analysis and ODEs · Mathematics 2020-10-21 Stefan Buschenhenke , Detlef Müller , Ana Vargas

Let $\{e_j\}$ be an orthonormal basis of Laplace eigenfunctions of a compact Riemannian manifold $(M,g)$. Let $H \subset M$ be a submanifold and let $\{\psi_k\}$ be an orthonormal basis of Laplace eigenfunctions of $H$ with the induced…

Analysis of PDEs · Mathematics 2023-01-24 Emmett L. Wyman , Yakun Xi , Steve Zelditch

In this work, we will present variants Fixed Point Theorem for the affine and classical contexts, as a consequence of general Brouwer's Fixed Point Theorem. For instance, the affine results will allow working on affine balls, which are…

Functional Analysis · Mathematics 2023-05-09 Anderson Luis Albuquerque de Araujo , Edir Junior Ferreira Leite

We study norm inequalities for the Fourier transform, namely, \begin{equation}\label{introduction} \|\widehat f\|_{X_{p,q}^\lambda} \lesssim \|f\|_{Y}, \end{equation} where $X$ is either a Morrey or Campanato space and $Y$ is an appropriate…

Classical Analysis and ODEs · Mathematics 2023-10-25 Alberto Debernardi Pinos , Erlan Nursultanov , Sergey Tikhonov

The spherical Fourier transform on a harmonic Hadamard manifold $(X^n, g)$ of positive volume entropy is studied. If $(X^n, g)$ is of hypergeometric type, namely spherical functions of $X$ are represented by the Gauss hypergeometric…

Differential Geometry · Mathematics 2020-05-28 Mitsuhito Itoh , Hiroyasu Satoh

We consider Fourier transforms of densities supported on curves in R^d. We obtain sharp lower and close to sharp upper bounds for the L^q decay rates.

Classical Analysis and ODEs · Mathematics 2010-03-15 Luca Brandolini , Giacomo Gigante , Allan Greenleaf , Alexander Iosevich , Andreas Seeger , Giancarlo Travaglini

Let $G$ be a locally compact Abelian group with a fixed Haar measure and, denote by $\widehat{G}$ its dual group. In this article, the authors obtain various boundedness of the short-time Fourier transform on Lorentz spaces:…

Classical Analysis and ODEs · Mathematics 2025-09-30 Jun Liu , Yaqian Lu , Xianjie Yan , Chi Zhang

We establish some weighted $L^2$ estimates for the Fourier extension operator in $\mathbb{R}^2$ and discuss several applications to $L^p$ problems. These include estimates for the maximal Schr\"odinger operator and the maximal extension…

Classical Analysis and ODEs · Mathematics 2025-06-04 Shukun Wu

We give an extension of Rubio de Francia's extrapolation theorem for functions taking values in UMD Banach function spaces to the multilinear limited range setting. In particular we show how boundedness of an $m$-(sub)linear operator…

Classical Analysis and ODEs · Mathematics 2024-05-31 Emiel Lorist , Zoe Nieraeth

We study $L^p$ boundedness of the maximal average over dilations of a smooth hypersurface $S$. When the decay rate of the Fourier transform of a measure on $S$ is $1/2$, we establish the optimal maximal bound, which settles the conjecture…

Classical Analysis and ODEs · Mathematics 2025-01-03 Sewook Oh

This note records an asymptotic improvement on the known $L^p$ range for the Fourier restriction conjecture in high dimensions. This is obtained by combining Guth's polynomial partitioning method with recent geometric results regarding…

Classical Analysis and ODEs · Mathematics 2020-10-07 Jonathan Hickman , Joshua Zahl

We give a proof of Fourier extension conjecture on the paraboloid in all dimensions bigger than 2 that begins with a decomposition suggested in Sawyer [Saw8] of writing a smooth Alpert projection as a sum of pieces whose Fourier extensions…

Classical Analysis and ODEs · Mathematics 2026-05-19 Cristian Rios , Eric T. Sawyer

In this article, the authors establish a general (two-weight) boundedness criterion for a pair of functions, $(F,f)$, on $\mathbb{R}^n$ in the scale of weighted Lebesgue spaces, weighted Lorentz spaces, (Lorentz--)Morrey spaces, and…

Analysis of PDEs · Mathematics 2021-12-09 Sibei Yang , Zhenyu Yang

We study the Fourier orthogonal expansions with respect to the Laguerre type weigh functions on the conic surface of revolution and the domain bounded by such a surface. The main results include a closed form formula for the reproducing…

Classical Analysis and ODEs · Mathematics 2021-03-09 Yuan Xu

In this paper we solve an open problem concerning the characterization of those measurable sets $\Omega\subset \mathbb{R}^{2d}$ that, among all sets having a prescribed Lebesgue measure, can trap the largest possible energy fraction in…

Classical Analysis and ODEs · Mathematics 2022-09-19 Fabio Nicola , Paolo Tilli

We refine the $L^p$ restriction estimates for Laplace eigenfunctions on a Riemannian surface, originally established by Burq, G\'erard, and Tzvetkov. First, we establish estimates for the restriction of eigenfunctions to arbitrary Borel…

Analysis of PDEs · Mathematics 2024-11-05 Chuanwei Gao , Changxing Miao , Yakun Xi

It is considered Fourier transform of convex analytic hypersufaces on $R^{4} $. We prove that the Fourier restriction operator associated to convex analytic hypersufaces is \textit{$(L_{p}, L_{2})$} bounded whenever $1\le p\le…

Classical Analysis and ODEs · Mathematics 2010-04-16 D. D. Turakulov