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We build on a recent paper on Fourier expansions for the Riemann zeta function. We establish Fourier expansions for certain $L$-functions, and offer series representations involving the Whittaker function $W_{\gamma,\mu}(z)$ for the…

Number Theory · Mathematics 2025-10-07 Alexander E. Patkowski

Quantitative formulations of Fefferman's counterexample for the ball multiplier are naturally linked to square function estimates for conical and directional multipliers. In this article we develop a novel framework for these square…

Classical Analysis and ODEs · Mathematics 2023-09-27 Natalia Accomazzo , Francesco Di Plinio , Paul Hagelstein , Ioannis Parissis , Luz Roncal

The optimal $L^4$-Strichartz estimate for the Schr{\"o}dinger equation on the two-dimensional rational torus $\mathbb{T}^2$ is proved, which improves an estimate of Bourgain. A new method based on incidence geometry is used. The approach…

Analysis of PDEs · Mathematics 2024-09-11 Sebastian Herr , Beomjong Kwak

The endpoint Strichartz estimate $\|e^{it\Delta} f\|_{L_t^2 L_x^\infty} \lesssim \|f\|_{L^2}$ is known to be false in two space dimensions. Taking averages spherically on the polar coordinates $x=\rho\omega$, $\rho>0$,…

Analysis of PDEs · Mathematics 2022-03-18 Jungkwon Kim , Yoonjung Lee , Ihyeok Seo

We improve the $L^p(\mathbb{R}^n)$ bounds on Stein's square function to the best-known range of the Fourier restriction problem when $n\geq4$. Applications including certain local smoothing estimates are also discussed.

Classical Analysis and ODEs · Mathematics 2021-09-15 Shengwen Gan , Changkeun Oh , Shukun Wu

We present a unified approach for obtaining global a priori estimates for solutions of nonlinear defocusing Schr\"odinger equations with defocusing nonlinearities. The estimates are produced by contracting the local momentum conservation…

Analysis of PDEs · Mathematics 2009-08-06 J. Colliander , M. Grillakis , N. Tzirakis

The problem of reconstruction a function from spherical means is at the heart of several modern imaging modalities and other applications. In this paper we derive universal back-projection type reconstruction formulas for recovering a…

Analysis of PDEs · Mathematics 2015-01-20 Markus Haltmeier

In the present paper, the coefficient estimates are found for the class $\mathcal S^{*-1}(\alpha)$ consisting of inverses of functions in the class of univalent starlike functions of order $\alpha$ in $\mathcal D=\{z\in\mathbb C:|z|<1\}$.…

Complex Variables · Mathematics 2007-05-23 G. P. Kapoor , A. K. Mishra

In this paper, we study the dispersive decay estimates for solution to the $3\mathrm{D}$ energy-critical nonlinear Schr\"odinger equation with an inverse-square operator $\mathcal{L}_a$ where the operator is denoted by…

Analysis of PDEs · Mathematics 2024-12-17 Jialu Wang , Chengbin Xu , Fang Zhang

In this paper we study sharp estimates for the Schr\"odinger operator via the framework of orthogonal polynomials. We use spherical harmonics and Gegenbauer polynomials to prove a new weighted inequality for the Schr\"odinger equation that…

Classical Analysis and ODEs · Mathematics 2017-08-28 Felipe Gonçalves

We prove new $L^p$-$L^q$-estimates for solutions to elliptic differential operators with constant coefficients in $\mathbb{R}^3$. We use the estimates for the decay of the Fourier transform of particular surfaces in $\mathbb{R}^3$ with…

Analysis of PDEs · Mathematics 2021-08-18 Robert Schippa

The purpose of this paper is to study the validity of global-in-time Strichartz estimates for the Schr\"odinger equation on $\mathbb{R}^n$, $n\ge3$, with the negative inverse-square potential $-\sigma|x|^{-2}$ in the critical case…

Analysis of PDEs · Mathematics 2017-05-09 Haruya Mizutani

Let $L$ be a linear operator in $L^2(\mathbb{R}^n)$ which generates a semigroup $e^{-tL}$ whose kernels $p_t(x,y)$ satisfy the Gaussian upper bound. In this paper, we investigate several kinds of weighted norm inequalities for the conical…

Classical Analysis and ODEs · Mathematics 2020-11-24 Mingming Cao , Zengyan Si , Juan Zhang

We establish certain square function estimates for a class of oscillatory integral operators with homogeneous phase functions. These results are employed to deduce a refinement of a previous result of Mockenhaupt Seeger and Sogge…

Analysis of PDEs · Mathematics 2019-01-23 Chuanwei Gao , Changxing Miao , Jianwei-Urbain Yang

We announce a local $T(b)$ theorem, an inductive scheme, and $L^p$ extrapolation results for $L^2$ square function estimates related to the analysis of integral operators that act on Ahlfors-David regular sets of arbitrary codimension in…

Analysis of PDEs · Mathematics 2014-01-31 Steve Hofmann , Dorina Mitrea , Marius Mitrea , Andrew J. Morris

We prove L^1 --> L^\infty estimates for linear Schroedinger equations in dimensions one and three. The potentials are only required to satisfy some mild decay assumptions. No regularity on the potentials is assumed.

Analysis of PDEs · Mathematics 2007-05-23 M. Goldberg , W. Schlag

We prove sharp local smoothing estimates for wave equations on compact Riemannian manifolds in $n+1$ dimensions for odd $n$ and obtain improved estimates in even dimensions. This is achieved by deriving local smoothing estimates for certain…

Analysis of PDEs · Mathematics 2026-01-06 Shengwen Gan , Danqing He , Xiaochun Li , Shukun Wu

We obtain Strichartz-type estimates for the fractional Schr\"odinger operator $f \mapsto e^{it(-\Delta)^{\gamma/2}} f$ over a time set $E$ of fractal dimension. To obtain those estimates capturing fractal nature of $E$, we employ the…

Analysis of PDEs · Mathematics 2025-09-16 Jin Bong Lee , Sanghyuk Lee , Luz Roncal

We generalise and offer a different proof of a recent $L^2$ square function estimate on UR sets by Hofmann, Mitrea, Mitrea and Morris. The proof is a short argument using the $\alpha$-numbers of Tolsa.

Classical Analysis and ODEs · Mathematics 2019-01-24 Henri Martikainen , Mihalis Mourgoglou

We consider the model of nonregular nonparametric regression where smoothness constraints are imposed on the regression function $f$ and the regression errors are assumed to decay with some sharpness level at their endpoints. The aim of…

Statistics Theory · Mathematics 2014-10-02 Moritz Jirak , Alexander Meister , Markus Reiß