EN
For any locally integrable f on ℝⁿ, we consider the operators S and T which average f over balls of radius |x| and center 0 and x, respectively:
$Sf(x) = 1/|B(0,|x|)| ∫_{B(0,|x|)} f(t)dt$, $Tf(x) = 1/|B(x,|x|)| ∫_{B(x,|x|)} f(t)dt$
for x ∈ ℝⁿ. The purpose of the paper is to establish sharp localized LlogL estimates for S and T. The proof rests on a corresponding one-weight estimate for a martingale maximal function, a result which is of independent interest.