In many cases, interacting fermions in one spatial dimension are described by the Luttinger model of free bosonic density excitations. Due to the absence of an interaction between these
bosonic degrees of freedom, the model is integrable. As a consequence, it does not relax back to equilibrium when one excites it via the local injection of electrons. Instead, it reaches
a non-equilibrium steady state with a peculiar electronic distribution function and spectral density. In the case of two co-propagating chiral channels, the non-perturbative method of
non-equilibrium bosonization allows to characterize the electron distribution by a fractional Fano factor and interpret it in terms of charge fractionalization.