  Recent advances in the field of quantum Monte Carlo simulations for impurity
problems allow --within dynamical mean field theory-- for a more thorough
investigation of the two-band Hubbard model with narrow/wide band and
SU(2)-symmetric Hund's exchange. The nature of this transition has been
controversial, and we establish that an orbital-selective Mott-Hubbard
transition exists. Thereby, the wide band still shows metallic behavior after
the narrow band became insulating -not a pseudogap as for an Ising Hund's
exchange. The coexistence of two solutions with metallic wide band and
insulating or metallic narrow band indicates, in general, first-order
transitions.
