  Initial conditions for cosmological N-body simulations are usually calculated
by rescaling the present day linear power spectrum obtained from an
Einstein-Boltzmann solver to the initial time employing the scale-independent
matter growth function. For the baseline Lambda-CDM model, this has been shown
to be consistent with General Relativity (GR) even in the presence of
relativistic species such as photons. We show that this approach is not
feasible in cosmologies with massive neutrinos and present an alternative
method employing the Newtonian motion gauge framework.
