The limiting weak type behaviors and The lower bound for a new weak $L\log L$ type norm of strong maximal operators

Moyan Qin, Huoxiong Wu, Qingying Xue

Published 2021-04-08Version 1

It is well known that the weak ($1,1$) bounds doesn't hold for the strong maximal operators, but it still enjoys certain weak $L\log L$ type norm inequality. Let $\Phi_n(t)=t(1+(\log^+t)^{n-1})$ and the space $L_{\Phi_n}({\mathbb R^{n}})$ be the set of all measurable functions on ${\mathbb R^{n}}$ such that $\|f\|_{L_{\Phi_n}({\mathbb R^{n}})} :=\|\Phi_n(|f|)\|_{L^1({\mathbb R^{n}})}<\infty$. In this paper, we introduce a new weak norm space $L_{\Phi_n}^{1,\infty}({\mathbb R^{n}})$, which is more larger than $L^{1,\infty}({\mathbb R^{n}})$ space, and establish the correspondng limiting weak type behaviors of the strong maximal operators. As a corollary, we show that $ \max\{{2^n}{((n-1)!)^{-1}},1\}$ is a lower bound for the best constant of the $L_{\Phi_n}\to L_{\Phi_n}^{1,\infty}$ norm of the strong maximal operators. Similar results have been extended to the multilinear strong maximal operators.