  We calculate the full $I-V$ characteristics at vanishing temperature in the
self-dual interacting resonant level model in two ways. The first uses careful
time dependent DMRG with large number of states per block and a representation
of the reservoirs as leads subjected to a chemical potential. The other is
based on integrability in the continuum limit, and generalizes early work of
Fendley Ludwig Saleur on the boundary sine-Gordon model. The two approaches are
in excellent agreement, and uncover among other things a power law decay of the
current at large voltages when $U>0$.
