Abstract. Let B be a locally integrable matrix function, W a matrix A p weight with 1 < p < ∞, and T be any of the Riesz transforms. We will characterize the boundedness of the commu-in terms of the membership of B in a natural matrix weighted BMO space. To do this, we will characterize the boundedness of dyadic paraproducts on L p (W ) via a new matrix weighted Carleson embedding theorem. Finally, we will use some of the ideas from these proofs to (among other things) obtain quantitative weighted norm inequalities for these operators and also use them to prove sharp L 2 bounds for the Christ/Goldberg matrix weighted maximal function associated with matrix A 2 weights.

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