Weak-type estimates in Morrey spaces for maximal commutator and commutator of maximal function

Abstract

In this paper it is shown that the Hardy-Littlewood maximal operator $M$ is not bounded on Zygmund-Morrey space $\mathcal{M}_{L(\log L),λ}$, but $M$ is still bounded on $\mathcal{M}_{L(\log L),λ}$ for radially decreasing functions. The boundedness of the iterated maximal operator $M^2$ from $\mathcal{M}_{L(\log L),λ}$ to weak Zygmund-Morrey space ${\mathcal {W \! M}}_{L(\log L),λ}$ is proved. The class of functions for which the maximal commutator $C_b$ is bounded from $\mathcal{M}_{L(\log L),λ}$ to ${\mathcal {W \! M}}_{L(\log L),λ}$ are characterized. It is proved that the commutator of the Hardy-Littlewood maximal operator $M$ with function $b \in BMO({\mathbb R}^n)$ such that $b^- \in L_{\infty}({\mathbb R}^n)$ is bounded from $\mathcal{M}_{L(\log L),λ}$ to ${\mathcal {W \! M}}_{L(\log L),λ}$. New pointwise characterizations of $M_α M$ by means of norm of Hardy-Littlewood maximal function in classical Morrey spaces are given.