  Metal insulator transitions driven by local Coulomb interactions are among
the most fascinating phenomena in condensed matter physics. They occur in a
large variety of transition metal compounds. Most of these strongly correlated
materials consist of valence bands derived from electronic d shells where
intra- and inter-orbital Coulomb interactions are equally important and where
the crystal structure splits the valence bands into narrow and wide subbands. A
fundamental question is whether these systems exhibit a common Mott transition,
implying all subbands to be either metallic or insulating, or successive
orbital dependent transitions, implying a coexistence region with metallic and
insulating behavior present in different subbands. Using the dynamical mean
field theory we show that inter-orbital Coulomb interactions lead to a single
Mott transition. Nevertheless, the subbands exhibit more or less strongly
correlated excitation spectra in the metallic phase and different band gaps in
the insulating phase.
