Baryogenesis from phase transitions below a GeV

The aim of the thesis is to build a baryogenesis model from First Order Phase Transitions (FOPTs) below a GeV, producing gravitational waves that could explain those recently observed by Pulsar Timing Arrays. Baryogenesis models aim to solve one of the open problems of the Standard Model, namely the asymmetry between matter and antimatter observed in the universe. In the last decades, many new physics models have been proposed to address this question, motivated by theoretical considerations and experimental opportunities. In particular, in this work, we consider a baryogenesis mechanism where a fermionic dark matter candidate and a neutron mix via an effective operator and the baryon asymmetry is produced at cosmological temperatures of O(10) MeV via resonant oscillations between neutron and dark matter. This idea can be implemented in a model with a dark U (1)′ gauge symmetry where the mass of the associated "dark" photon is generated via a "dark" Higgs mechanism. The main novelty of this work is that we assume that the potential of the dark Higgs scalar is scale invariant and that its vacuum expectation value (VEV) is generated by radiative corrections at one-loop, as in the Coleman-Weinberg model. The VEV enters in the mass mixing term and, ultimately, in the baryon asymmetry. This effective potential at one loop induces a supercool FOPT and lead to the generation of Gravitational Waves (GWs). We find that the parameters of our model yielding to successful baryogenesis could also explain the recent GWs observation at Pulsar Timing Arrays.