  We investigate the two-orbital Hubbard model in infinite dimensions by means
of the self-energy functional method. By calculating the entropy,
susceptibility, and quasi-particle weight at zero temperature, we determine the
phase diagram for the system with same and different bandwidths, which is
compared with that obtained recently. It is clarified that orbital fluctuations
play a key role in controlling the nature of the Mott transitions in the
system.
