Fully relativistic treatment of decaying cold dark matter in $N$-body simulations

Understand

We present $N$-body simulations in which either all, or a fraction of, the cold dark matter decays non-relativistically to a relativistic, non-interacting dark radiation component.

• All effects from radiation and general relativity are self-consistently included at the level of linear perturbation theory, and our simulation results therefore match those from linear Einstein-Boltzmann codes such as CLASS in the appropriate large-scale limit.
• We also find that standard, Newtonian $N$-body simulations adequately describe the non-linear evolution at smaller scales ($k \gtrsim 0.1 \, h/{\mathrm{Mpc}}$) in this type of model, provided that the mass of the decaying component is modified correctly, and that the background evolution is correctly treated.
• That is, for studies of small scales, effects from general relativity and radiation can be safely neglected.