EN
Let T be a power-bounded operator on a (real or complex) Banach space. We study the convergence of the one-sided ergodic Hilbert transform $lim_{n} ∑_{k=1}^{n} (T^{k}x)/k$. We prove that weak and strong convergence are equivalent, and in a reflexive space also $sup_{n} ||∑_{k=1}^{n} (T^{k}x)/k|| < ∞$ is equivalent to the convergence. We also show that $-∑_{k=1}^{∞} (T^{k})/k$ (which converges on (I-T)X) is precisely the infinitesimal generator of the semigroup $(I-T)^{r}_{|\overline{(I-T)X}}$.