A Newtonian Motion Gauge found via Einstein-Boltzmann solver maps linear dynamics with scale-dependent growth and GR corrections to Newtonian equations, enabling consistent nonlinear EFT calculations that are transformed back for accuracy in real and redshift space.
Relativistic initial conditions for N-body simulations
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abstract
Initial conditions for (Newtonian) cosmological N-body simulations are usually set by re-scaling the present-day power spectrum obtained from linear (relativistic) Boltzmann codes to the desired initial redshift of the simulation. This back-scaling method can account for the effect of inhomogeneous residual thermal radiation at early times, which is absent in the Newtonian simulations. We analyse this procedure from a fully relativistic perspective, employing the recently-proposed Newtonian motion gauge framework. We find that N-body simulations for LambdaCDM cosmology starting from back-scaled initial conditions can be self-consistently embedded in a relativistic space-time with first-order metric potentials calculated using a linear Boltzmann code. This space-time coincides with a simple "N-body gauge" for z<50 for all observable modes. Care must be taken, however, when simulating non-standard cosmologies. As an example, we analyse the back-scaling method in a cosmology with decaying dark matter, and show that metric perturbations become large at early times in the back-scaling approach, indicating a breakdown of the perturbative description. We suggest a suitable "forwards approach" for such cases.
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UNVERDICTED 2representative citing papers
COLA-based hybrid emulator reproduces nonlinear power spectrum boosts in w0wa models to <2% error vs EuclidEmulator2 and produces <0.3σ shifts in LSST-like cosmic shear parameter constraints.
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Effective Field Theory of Large Scale Structure and Newtonian Motion Gauges
A Newtonian Motion Gauge found via Einstein-Boltzmann solver maps linear dynamics with scale-dependent growth and GR corrections to Newtonian equations, enabling consistent nonlinear EFT calculations that are transformed back for accuracy in real and redshift space.
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Modeling nonlinear scales for dynamical dark energy cosmologies with COLA
COLA-based hybrid emulator reproduces nonlinear power spectrum boosts in w0wa models to <2% error vs EuclidEmulator2 and produces <0.3σ shifts in LSST-like cosmic shear parameter constraints.