We establish an optimal Calderón-Zygmund theory for nonuniformly elliptic double phase problems with matrix weights. For 11, (| F|ᵖ+a (x) | F|q) L^γ₋₎₂ \;\; (| Du|ᵖ+a (x) | Du|q) L^γ₋₎₂. Our argument combines a freezing of the logarithm of the matrix field, , with a fractional maximal-operator method governed by the Muckenhoupt-Wheeden A, ₒ classes (where 1/s=1/p-α/ (nq) ). This yields scale-invariant comparison and level-set estimates and precludes Lavrentiev gaps at the sharp threshold q/p 1+α/n. Our result recovers the identity case \, Iₙ\, , i. e. , the classical (unweighted) Calderón-Zygmund theory for double-phase problems.
Byun et al. (Tue,) studied this question.