Variation of Calderón--Zygmund Operators with Matrix Weight

Abstract: Let $p\in(1,\infty)$, $\rho\in (2, \infty)$ and $W$ be a matrix $A_p$ weight. In this article, we introduce a version of variation $\mathcal{V}{\rho}({\mathcal T_n}{\,,\,\ast})$ for matrix Calder\'on--Zygmund operators with modulus of continuity satisfying the Dini condition. We then obtain the $L^p(W)$-boundedness of $\mathcal{V}{\rho}({\mathcal T_n}{\,,\,\ast})$ with norm \begin{align*} |\mathcal{V}{\rho}({\mathcal T_n}{\,,\,\ast})|{L^p(W)\to L^p(W)}\leq C[W]{A_p}^{1+{1\over p-1} -{1\over p}} \end{align*} by first proving a sparse domination of the variation of the scalar Calder\'on--Zygmund operator, and then providing a convex body sparse domination of the variation of the matrix Calder\'on--Zygmund operator. The key step here is a weak type estimate of a local grand maximal truncated operator with respect to the scalar Calder\'on--Zygmund operator.