EN
We answer a question of H. Furstenberg on the pointwise convergence of the averages
$1/N ∑_{n=1}^{N} Uⁿ(f·Rⁿ(g))$,
where U and R are positive operators. We also study the pointwise convergence of the averages
$1/N ∑_{n=1}^{N} f(Sⁿx)g(Rⁿx)$
when T and S are measure preserving transformations.