Matter-power-spectrum distinction between thermal and non-thermal secluded dark matter

Determine the observational difference in the matter power spectrum between thermal and non-thermal secluded dark matter distributions by carrying out a dedicated cosmological-perturbation-theory analysis.

Background

The paper studies a secluded real-scalar dark-matter scenario produced through perturbative inflaton decay and subsequently subject to quartic self-interactions. Depending on the self-coupling, the dark-matter momentum distribution may thermalize toward a Maxwell–Boltzmann form or remain non-thermal, while both cases can satisfy the considered BBN, CMB, and large-scale-structure constraints.

The authors note that the parameter region in which the momentum distribution remains non-thermal is nevertheless cosmologically allowed. They identify the matter power spectrum as a potential observable capable of distinguishing the thermal and non-thermal cases, but leave the required cosmological perturbation-theory calculation unresolved.