"Fermion Soliton Black Holes" and "Quasinormal modes and quasibound states around black holes: structure and transitions for scalar fields"

Wednesday 8 Oct 2025, 13:00 → 14:00 Europe/Rome

Sala Lauree

First talk: "We lack certainty about what truly lies inside black holes.  Although observational evidence for black holes continues to grow, no robust theoretical argument has yet provided a concrete resolution to the problem of the gravitational singularities that may be concealed within them. In spite of the Hawking–Penrose theorems of general relativity, it is widely believed that singularities are actually a byproduct of the breakdown of the classical theory at Planckian scales. In the absence of a complete quantum gravity theory, a pragmatic approach is to construct classical effective singularity-free black hole spacetimes, either within modified-gravity frameworks or with specific gravity–matter models: regular black holes.Within this context, the goal pursued by this thesis is to verify or disprove the existence of non-rotating regular black hole configurations in a specific fermion scalar matter theory, minimally coupled to Einstein gravity. We refer to these hypothetical configurations as fermion soliton black holes. This goal is indeed achieved, as we show that the theory cannot admit solutions of this kind. We investigate fermion soliton black holes in two settings: spacetimes admitting isotropic spherical coordinates and spacetimes admitting standard spherical coordinates.In isotropic spherical coordinates, we prove a proposition that identifies mutually isomorphic regions that can arise in solutions of generic gravity–matter theories; applying it to the fermion scalar theory rules out regular black hole spacetimes. In standard spherical coordinates, we establish a no-go theorem for broad classes of theories: if the stress–energy tensor satisfies a specific component condition, the admissible radial arrangement of static and non-static regions is constrained; for the fermion scalar theory, this constraint excludes regular black holes."

Second talk:"Axions are among the most promising dark matter candidates beyond the Standard Model. However their extremely weak interactions with ordinary matter make them very challenging to detect using traditional particle physics experiments. Black Holes, on the other hand, may offer a natural evironment to probe axions through different phenomena. In this talk i will discuss how a relativistic perturbation theory framework can yield observational predictions that could be within the reach of next generation gravitational wave inteferometer."