Speaker
Description
Axions are pseudo-Nambu-Goldstone bosons that provide a cogent solution to the strong CP problem. They are expected to have a rich phenomenology, stemming from their postulated couplings to Standard Model particles.
In this talk, we focus on neutron star (NS) astrophysics and on the axion-photon coupling, which modifies Maxwell’s equations. We show that the expectation value of the axion field can become large at the typical densities expected in NS cores, compared to the vacuum case. Such shift affects the magnetic and thermal evolution of NSs, leading to potentially observable effects. By performing state-of-the-art magneto-thermal simulations of NSs, we show that axion-induced perturbations to
the NS magnetic field grow rapidly. The electric currents circulating in the resistive crustal layers become more intense, causing enhanced ohmic dissipation, heating the crust and increasing the observable NS thermal luminosity. The growth of axion-induced magnetic field perturbations and
the consequent internal heating effect are controlled by axion parameters such as the axion decay constant and axion couplings. By preventing the uncontrolled growth of axion-induced magnetic
field perturbations, we place constraints on axion parameters and couplings with our magneto-thermal simulations, in agreement with the latest data from the population of thermally-emitting NSs and magnetars.
