Linear Perturbations in a coupled cosmon-bolon cosmology

TL;DR

This paper studies linear perturbations in a coupled scalar field dark matter and quintessence model, providing analytical and numerical methods to predict structure formation and setting a lower bound on the dark matter particle mass.

Contribution

It introduces an analytical averaging mechanism for oscillations and applies it to predict matter power spectra and halo counts in a coupled cosmon-bolon cosmology.

Findings

Lower bound on bolon mass ~9 x 10^{-22} eV

Predicted matter power spectra and halo counts

Discussed ambiguities in the formalism

Abstract

We investigate linear perturbations in the recently proposed cosmon-bolon model of coupled scalar field dark matter and quintessence. We provide an analytical mechanism to average over the quick oscillations appearing both in the background and at the perturbative level and evolve the effective equations numerically. The resulting matter power spectra are used to predict total halo number counts as well as substructure abundances in a typical galaxy by employing the extended Press-Schechter excursion set approach. We discuss in some detail the ambiguities arising in this formalism, starting from issues with generalizing spherical collapse to our model to filter choices and different barriers. The results are used to put a lower bound on the current bolon mass of roughly $9 \times 10^{-22}$ eV.