  We study theoretically the Mott metal-insulator transition for a system of
fermionic atoms confined in a three-dimensional optical lattice and a harmonic
trap. We describe an inhomogeneous system of several thousand sites using an
adaptation of dynamical mean field theory solved efficiently with the numerical
renormalization group method. Above a critical value of the on-site
interaction, a Mott-insulating phase appears in the system. We investigate
signatures of the Mott phase in the density profile and in time-of-flight
experiments.
