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.
Highlights
To look for its imprints in the abundance of the primordial elements
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 have investigated the effect of ultralight scalar DM with universal quadratic couplings to SM fields on predictions of Big-Bang Nucleosynthesis (BBN)
Summary
We assume that any possible self-interaction of φ can be neglected, whereas its couplings to the SM fields preserve the WEP This implies that φ is coupled to the SM through the effective metric (eq (1.1)). From the expression (eq (2.3)) for the interaction Lagrangian in the Einstein frame we see that the presence of SM matter with energy density ρSM and pressure pSM induces a contribution into the mass term of φ leading to an effective time-dependent mass, m2φ,eff m2φ. We do not attempt to add anything to its solution and just speculate that the cancellation of vacuum energy can happen separately within the SM sector (or its extension universally coupled to φ) implying ρvSaMc ρvtoatc In this case the effect of quantum corrections (eq (2.13)) is completely negligible
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