  The ground-state phase diagram of the asymmetric Hubbard model is studied in
one and two dimensions by a well-controlled numerical method. The method allows
to calculate directly the probabilities of particular phases in the approximate
ground-state and thus to specify the stability domains corresponding to phases
with the highest probabilities. Depending on the electron filling $n$ and the
magnitude of the asymmetry $t_f/t_d$ between the hopping integrals of $f$ and
$d$ electrons two different scenarios in formation of ground states are
observed. At low electron fillings ($n\leq 1/3$) the ground states are always
phase segregated in the limit of strong asymmetry ($t_d\gg t_f$). With
decreasing asymmetry the system undergoes a transition to the phase separated
state and then to the homogeneous state. For electron fillings $n>1/3 $ and
weak Coulomb interactions the ground state is homogeneous for all values of
asymmetry, while for intermediate and strong interactions the system exhibits
the same sequence of phase transitions as for $n$ small. Moreover, it is shown
that the segregated phase is significantly stabilized with increasing electron
filling, while the separated phases disappear gradually from the ground-state
phase diagrams.
