Deciphering the Archaeological Record: Cosmological Imprints of Non-Minimal Dark Sectors

Abstract

Many proposals for physics beyond the Standard Model give rise to a dark sector containing many degrees of freedom. In this work, we explore the cosmological implications of the non-trivial dynamics which may arise within such dark sectors, focusing on decay processes which take place entirely among the dark constituents. First, we demonstrate that such decays can leave dramatic imprints on the resulting dark-matter phase-space distribution. In particular, this distribution need not be thermal -it can even be multi-modal, exhibiting a non-trivial pattern of peaks and troughs as a function of momentum. We then proceed to show how these features can induce small-scale modifications to the matter power spectrum. Finally, we assess the extent to which one can approach the archaeological "inverse" problem of deciphering the properties of an underlying dark sector from the matter power spectrum. Indeed, one of the main results of this paper is a remarkably simple conjectured analytic expression which permits the reconstruction of many of the important features of the dark-matter phase-space distribution directly from the matter power spectrum. Our results therefore provide an interesting toolbox of methods for learning about, and potentially constraining, the features of non-minimal dark sectors and their dynamics in the early universe.

Stasis in an Expanding Universe: A Recipe for Stable Mixed-Component Cosmological Eras

“…As discussed in Ref. [40], the phase space of the φ particles could therefore be rather non-trivial at the time t (0) . Indeed, this distortion of the phase space could be viewed as introducing an additional initial "edge" effect that would also have to be taken into account in our analysis.…”

“…In either case, such non-trivial dynamics will produce a non-trivial time evolution for the background cosmology. This in turn could affect all sectors of the corresponding theory, including its dark sector, and thereby leave interesting signatures in the matter power spectrum [40] and corresponding halo-mass distributions [41].…”