Improving bounds for singular operators via Sharp Reverse Hölder Inequality for $A_{\infty}$

In this expository article we collect and discuss some recent results on different consequences of a Sharp Reverse Hölder Inequality for $A_{\infty}$ weights. For two given operators $T$ and $S$, we study $L^p(w)$ bounds of Coifman-Fefferman type. $\|Tf\|_{L^p(w)}\le c_{n,w,p} \|Sf\|_{L^p(w)},$ that can be understood as a way to control $T$ by $S$. We will focus on a \emph{quantitative} analysis of the constants involved and show that we can improve classical results regarding the dependence on the weight $w$ in terms of Wilson's $A_{\infty}$ constant $[w]_{A_{\infty}}:=\sup_Q\frac{1}{w(Q)}\int_Q M(wχ_Q).$ We will also exhibit recent improvements on the problem of finding sharp constants for weighted norm inequalities involving several singular operators. We obtain mixed $A_{1}$--$A_{\infty}$ estimates for the commutator $[b,T]$ and for its higher order analogue $T^k_{b}$. A common ingredient in the proofs presented here is a recent improvement of the Reverse Hölder Inequality for $A_{\infty}$ weights involving Wilson's constant.

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