Rome Samanta
Institute of Physics of the Czech Academy of Sciences, Czech Republic

Abstract
Strong upper limits on the electric dipole moment of neutron show that strong interactions are CP symmetric, although the SM as a whole is not. The CP violation in the strong interaction is characterized by the angle θ, which is bounded from above: θ < 10^-10 . The required vanishingly small value of the θ parameter is the strong CP problem. The classic solution to this is to promote θ as a pseudoscalar axion field resulting from a global U (1) symmetry breaking–the Peccei-Quinn (PQ) mechanism. When axion obtains its potential through QCD effects, remarkably, θ relaxes to zero (ground state of the potential) and solves the strong CP problem. Interestingly, besides solving the strong CP problem, axions could constitute the entire cold dark matter energy density if they are incredibly light; m a ≃ 10^-5 eV. For axion dark matter production, generally, misalignment mechanism, and decay of topological defects such as cosmic strings are considered. I shall discuss a new production mechanism of axion dark matter via parametric resonance oscillation of PQ field which leads to relatively heavy axion dark matter candidate m a ≃ 10^-2 eV, interesting for stellar evolution.

2023 July 26, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto