Speaker: Marco Calzà (University of Coimbra)
Title: Primordial black holes as laboratories for physics beyond the standard scenarios
We use the evaporation of primordial black holes (PBHs), of mass between 10^8 -10^12 kg, as a laboratory to investigate physics beyond the standard model of particles and to probe the structure of black holes. We show that PBHs develop non-negligible spins through Hawking's emission of a large number of axion-like particles generically present in string theory compactifications. This is because scalars can be emitted in the monopole mode (l = 0), where no angular momentum is removed from the BH, so a sufficiently large number of scalars can compensate for the spin-down produced by fermion, gauge boson, and graviton emission. This yields a unique probe of the total number of light scalars in the fundamental theory, independent of how weakly they interact with known matter. We propose a method to determine the mass and spin of PBHs based on measuring the energy of specific features in the photon Hawking emission spectrum, including both primary and secondary components. Since the proposed method relies on the energy of the photons emitted by a given PBH, rather than on the associated flux, it is independent of the PBH-Earth distance and, as a byproduct, can also be used to infer the latter. We study a regular rotating black hole, described by the Kerr-black-bounce metric, evaporating under the Hawking emission of a single scalar field. We compare the results with a Kerr black hole evaporating under the same conditions. The gray-body factors, the asymptotic final spin, the surface gravity, and as a consequence temperature, primary emissivity, and lifetime, are affected by the regularizing parameter. We briefly comment on the possibility of investigating the beyond-the-horizon structure of a black hole exploiting its Hawking emission.
Room: Sala de Reuniões e Seminários (2-8.3) (2nd Floor of Physics Building)