Constraints on ultralight scalar dark matter with quadratic couplings

Ultralight dark matter is a compelling candidate. In this work, we examine the impact of quadratically-coupled ultralight on predictions Big Bang Nucleosynthesis. The presence can modify effective values fundamental constants during Nucleosynthesis, modifying predicted abundances primordial elements such as Helium-4. We improve upon existing literature in two ways: firstly, take into account thermal mass acquired by due to its quadratic interactions with Standard Model bath, which affects cosmological evolution matter. Secondly, treat weak freeze-out using full kinetic equations instead an instantaneous approximation. Both improvements were shown Helium-4 prediction context universally-coupled previous work. extend these lessons more general couplings. show that modifications, Nucleosynthesis provides strong constraints couplings for large range masses compared other probes model, equivalence principle tests, atomic and nuclear clocks, well astrophysical probes.