DOI: 10.1515/gmj-2023-2115 ISSN: 1072-947X

A note on maximal estimate for an oscillatory operator

Jiawei Shen, Yali Pan
  • General Mathematics

Abstract

We study the local maximal oscillatory integral operator

T α , β ( f ) ( x ) = sup 0 < t < 1 | n e i | t ξ | α | t ξ | β Ψ ( | t ξ | ) f ^ ( ξ ) e 2 π i x , ξ 𝑑 ξ | , \displaystyle T_{\alpha,\beta}^{\ast}(f)(x)=\sup_{0<t<1}\Bigg{|}\int_{\mathbb{% R}^{n}}\frac{e^{i|t\xi|^{\alpha}}}{|t\xi|^{\beta}}\Psi(|t\xi|)\widehat{f}(\xi)% e^{2\pi i\langle x,\xi\rangle}\,d\xi\Bigg{|},

where

α ( 0 , 1 ) {\alpha\in(0,1)}
,
β > 0 {\beta>0}
, and Ψ is a cutoff function that vanishes in a neighborhood of the origin. First, in the case
0 < p < 1 {0<p<1}
, we obtain the
H p ( n ) L p ( n ) {{{H^{p}}({{\mathbb{R}^{n}}})}\rightarrow{{L^{p}({{\mathbb{R}^{n}}})}}}
boundedness of
T α , β {T_{\alpha,\beta}^{\ast}}
with the sharp relation among
α , β {\alpha,\beta}
and p. Then, using interpolation, we obtain the
L p ( n ) {{{L^{p}({{\mathbb{R}^{n}}})}}}
boundedness on
T α , β {T_{\alpha,\beta}^{\ast}}
when
p > 1 {p>1}
, which is an improvement of the recent result by Kenig and Staubach. At the critical case
p = 1 {p=1}
and
β = n α 2 {\beta=\frac{n\alpha}{2}}
, we show
T α , β : B q ( n ) L 1 , ( n ) {T_{\alpha,\beta}^{\ast}:B_{q}({\mathbb{R}^{n}})\rightarrow L^{1,\infty}({% \mathbb{R}^{n}})}
, where
B q ( n ) {B_{q}({\mathbb{R}^{n}})}
is the block space introduced by Lu, Taibleson and Weiss in order to study the almost every convergence of the Bochner–Riesz means at the critical index. As a further application, we obtain the convergence speed of a combination to the fractional Schrödinger operators
{ e i t k | | α } {\{e^{itk|\triangle|^{\alpha}}\}}
.