Establish sufficiency of the Lorentz–Muckenhoupt condition above the target index

Prove or disprove that \(w\in A_{(p,r),(q,s)}\) is sufficient for boundedness of \(M_\alpha:L_w^{p,r}\to L_w^{q,s}\) when \(p>1\), \(p<r\le s\), and \(s>q\).

Background

For p<rsp<r\le s with s>qs>q, the paper establishes the Lorentz–Muckenhoupt condition as necessary for the weighted maximal-operator estimate. Unlike the case r=pr=p, the paper does not establish a matching sufficiency theorem, leaving open whether the displayed condition gives the exact characterization.

References

In particular, it remains open whether $A_{(p,r),(q,s)}$ is sufficient for the above boundedness.

Properties and applications of Lorentz--Muckenhoupt classes  (2608.17918 - Wang et al., 18 Aug 2026) in Remark 4.17 (Remark \ref{rem:LILO}), Section 4