Weighted estimates for Hardy-Littlewood maximal functions on Harmonic $NA$ groups

TL;DR

This paper investigates the weighted boundedness of the Hardy-Littlewood maximal operator on Harmonic $NA$ groups, establishing $A_p$ weight conditions, endpoint inequalities, and providing examples including spherical functions.

Contribution

It introduces a suitable $A_p$ weight framework for Harmonic $NA$ groups and proves the weighted $L^p$ boundedness of the maximal operator, including endpoint and vector-valued inequalities.

Findings

Weighted $L^p$ boundedness of the maximal operator established.

Endpoint Fefferman-Stein inequality proved.

Spherical functions shown as examples of $A_p$ weights.

Abstract

Our aim in this article is to study the weighted boundedness of the centered Hardy-Littlewood maximal operator in Harmonic $NA$ groups. Following Ombrosi et al. \cite{ORR}, we define a suitable notion of $A_p$ weights, and for such weights, we prove the weighted $L^p$-boundedness of the maximal operator. Furthermore, as an endpoint case, we prove a variant of the Fefferman-Stein inequality, from which vector-valued maximal inequality has been established. We also provide various examples of weights to substantiate many aspects of our results. In particular, we have shown certain spherical functions of the Harmonic $NA$ group constitute examples of $A_p$ weights. The purely exponential volume growth property of the Harmonic $NA$ group has played a crucial role in our proofs.