Kavli Affiliate: Salman Habib
| First 5 Authors: James M. Sullivan, J. D. Emberson, Salman Habib, Nicholas Frontiere,
| Summary:
Neutrino mass constraints are a primary focus of current and future
large-scale structure (LSS) surveys. Non-linear LSS models rely heavily on
cosmological simulations — the impact of massive neutrinos should therefore be
included in these simulations in a realistic, computationally tractable, and
controlled manner. A recent proposal to reduce the related computational cost
employs a symmetric neutrino momentum sampling strategy in the initial
conditions. We implement a modified version of this strategy into the
Hardware/Hybrid Accelerated Cosmology Code (HACC) and perform convergence tests
on its internal parameters. We illustrate that this method can impart
$mathcal{O}(1%)$ numerical artifacts on the total matter field on small
scales, similar to previous findings, and present a method to remove these
artifacts using Fourier-space filtering of the neutrino density field.
Moreover, we show that the converged neutrino power spectrum does not follow
linear theory predictions on relatively large scales at early times at the
$15%$ level, prompting a more careful study of systematics in particle-based
neutrino simulations. We also present an improved method for backscaling linear
transfer functions for initial conditions in massive neutrino cosmologies that
is based on achieving the same relative neutrino growth as computed with
Boltzmann solvers. Our self-consistent backscaling method yields sub-percent
accuracy in the total matter growth function. Comparisons for the non-linear
power spectrum with the Mira-Titan emulator at a neutrino mass of
$m_{nu}=0.15~mathrm{eV}$ are in very good agreement with the expected level
of errors in the emulator and in the direct N-body simulation.
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