Snowmass2021 Cosmic Frontier White Paper: Cosmological Simulations for
  Dark Matter Physics
  Over the past several decades, unexpected astronomical discoveries have been
fueling a new wave of particle model building and are inspiring the next
generation of ever-more-sophisticated simulations to reveal the nature of Dark
Matter (DM). This coincides with the advent of new observing facilities coming
online, including JWST, the Rubin Observatory, the Nancy Grace Roman Space
Telescope, and CMB-S4. The time is now to build a novel simulation program to
interpret observations so that we can identify novel signatures of DM
microphysics across a large dynamic range of length scales and cosmic time.
This white paper identifies the key elements that are needed for such a
simulation program. We identify areas of growth on both the particle theory
side as well as the simulation algorithm and implementation side, so that we
can robustly simulate the cosmic evolution of DM for well-motivated models. We
recommend that simulations include a fully calibrated and well-tested treatment
of baryonic physics, and that outputs should connect with observations in the
space of observables. We identify the tools and methods currently available to
make predictions and the path forward for building more of these tools. A
strong cosmic DM simulation program is key to translating cosmological
observations to robust constraints on DM fundamental physics, and provides a
connection to lab-based probes of DM physics.
