Fourier decay and endpoint estimates for lacunary maximal operators

Abstract

We study endpoint estimates for lacunary maximal operators associated with compactly supported measures. For every $d\geq1$, we construct a compactly supported, absolutely continuous probability measure on $\mathbb R^d$ with polynomial Fourier decay whose associated lacunary maximal operator fails to map $H^1(\mathbb R^d)$ boundedly into $L^{1,\infty}(\mathbb R^d)$. In particular, it fails to be of weak type $(1,1)$. This gives a negative answer to the weak type $(1,1)$ question posed by Seeger and Wright in 2011 and to Open Problems 14 and 15, contributed by Wright at the 2016 Conference in Harmonic Analysis, held at the University of Wisconsin--Madison in honor of Professor Michael Christ.