On the spin paradigm and the radio dichotomy of quasars

We investigate whether models based on the assumption that jets in quasars are powered by rotating black holes can explain the observed radio dichotom y of quasars. We show that in terms of the 'spin paradigm' models, radio-lo ud quasars could be objects in which the rotation rate of the black hole co rresponds to an equilibrium between spin-up by accretion and spin-down by t he Blandford-Znajek mechanism. Radio-quiet quasars could be hosting black h oles with an average spin much smaller than the equilibrium one. We discuss possible accretion scenarios which can lead to such a bimodal distribution of black hole spins.