Mixed weak estimates of Sawyer type for generalized maximal operators

Abstract

We study mixed weak estimates of Sawyer type for maximal operators associated to the family of Young functions $\Phi (t)=t^r(1+{\log }^{+}t{)}^{\delta }$, where $r\ge 1$ and $\delta \ge 0$. More precisely, if $u$ and $v^r$ are $A_1$ weights, and $w$ is defined as $w=1/\Phi (v^{-1})$ then the following estimate \[uw\left(\left\{x\in \mathbb{R}^n: \frac{M_Φ(fv)(x)}{v(x)} > t\right\}\right) \leq C\int_{\mathbb{R}^n} Φ\left(\frac{|f(x)|v(x)}{t}\right)u(x) \,dx\] holds for every positive $t$. This extends mixed estimates to a wider class of maximal operators, since when we put $r=1$ and $\delta =0$ we recover a previous result for the Hardy-Littlewood maximal operator. This inequality generalizes some previous results proved by Cruz Uribe, Martell and Pérez in (Int. Math. Res. Not. (30): 1849-1871, 2005). Moreover, it includes estimates for some maximal operators related with commutators of Calderón-Zygmund operators.

14 pages