  We study the Haldane-Hubbard model by exact Renormalization Group techniques.
We construct the topological phase diagram, for weak interactions. We predict
that many-body interactions induce a shift of the transition line. The presence
of new intermediate phases, absent in the non interacting case, is rigorously
excluded at weak coupling. Despite the nontrivial renormalization of the wave
function and of the Fermi velocity, the conductivity is universal: at the
renormalized critical line, both the discontinuity of the transverse
conductivity and the longitudinal conductivity do not depend on the
interaction, thanks to remarkable cancellations due to lattice Ward Identities.
