Weak endpoint bounds for matrix weights

We prove quantitative, matrix weighted, endpoint estimates for the matrix weighted Hardy–Littlewood maximal operator, Calderón–Zygmund operators, and commutators of CZOs with scalar BMO functions, when the matrix weight is in the class A${}_1$ introduced by M. Frazier and S. Roudenko. Even in the scalar case, our estimates are sharper than the results implicit in the literature.