Fast simulations of cosmic large-scale structure with massive neutrinos
  Accurate cosmological simulations that include the effect of non-linear
matter clustering as well as of massive neutrinos are essential for measuring
the neutrino mass scale from upcoming galaxy surveys. Typically, Newtonian
simulations are employed and the neutrino distribution is sampled with a large
number of particles in order to beat down the shot noise. Here we perform very
efficient simulations with light massive neutrinos which require virtually no
extra cost over matter-only simulations, and furthermore do not require tracer
particles for the neutrinos. Instead, we use a weak-field dictionary based on
the recently developed Newtonion motion approach, where Newtonian simulations
for matter are paired with a linear relativistic Boltzmann code to allow for an
absorption of the neutrino evolution into a time-dependent coordinate
transformation. For this, only minimal modifications in existing N-body codes
are required, which we have explicitly implemented in $\textit{gevolution}$ and
$\textit{gadget-2}$. Our fast method determines the non-linear matter power
spectrum to permille-level precision when compared against state-of-the-art
simulations that have been performed for $0.1\,{\rm eV} \leq \sum m_\nu \leq
0.3\,$eV.
