BBN constraints on universally-coupled ultralight scalar dark matter

TL;DR

This paper investigates how ultralight scalar dark matter interacting universally with Standard Model particles influences Big Bang Nucleosynthesis, deriving constraints from helium-4 abundance measurements that surpass other probes.

Contribution

It models the cosmological evolution of such dark matter, incorporating environmental effects on scalar mass and analyzing BBN in both Einstein and Jordan frames.

Findings

Helium-4 abundance measurements impose strong constraints on dark matter parameters.

Constraints are significantly affected by environmental scalar mass and neutron freeze-out dynamics.

BBN constraints are more stringent than other observational probes for most parameter space.

Abstract

Ultralight scalar dark matter can interact with all massive Standard Model particles through a universal coupling. Such a coupling modifies the Standard Model particle masses and affects the dynamics of Big Bang Nucleosynthesis. We model the cosmological evolution of the dark matter, taking into account the modifications of the scalar mass by the environment as well as the full dynamics of Big Bang Nucleosynthesis. We find that precision measurements of the helium-4 abundance set stringent constraints on the available parameter space, and that these constraints are strongly affected by both the dark matter environmental mass and the dynamics of the neutron freeze-out. Furthermore, we perform the analysis in both the Einstein and Jordan frames, the latter of which allows us to implement the model into numerical Big Bang Nucleosynthesis codes and analyze additional light elements. The numerical analysis shows that the constraint from helium-4 dominates over deuterium, and that the effect on lithium is insufficient to solve the lithium problem. Comparing to several other probes, we find that Big Bang Nucleosynthesis sets the strongest constraints for the majority of the parameter space.