Free Streaming in Warm Wave Dark Matter

Understand

We provide a framework for numerically computing the effects of free-streaming in scalar fields produced after inflation.

• First, we provide a detailed prescription for setting up initial conditions in the field.
• This prescription allows us to specify the power spectra of the fields (peaked on subhorizon length scales and without a homogeneous field mode), and importantly, also correctly reproduces the behaviour of density perturbations on large length scales consistent with superhorizon adiabatic perturbations.
• We then evolve the fields using a spatially inhomogeneous Klein-Gordon equation, including the effects of expansion and radiation-sourced metric perturbations.