HEP Colloquia 2022

by Mr Andrea Pierfrancesco Sanna (University of Cagliari)

Wednesday 29 Mar 2023, 14:30 → 16:30 Europe/Rome

Aula Consiliare (Department of Physics)

Effective models of nonsingular quantum black holes

Penrose's singularity theorem proved the utter inevitability of spacetime singularity formation in general relativity during gravitational collapse, where the theory completely loses its predictive powers. It is generally believed that this problem will find a solution in a theory of quantum gravity (QG), whose effects have so far been assumed to act at the Planck length. Instead, this talk explores the possibility that smearing of the singularity may be related to QG effects acting at the event horizon scale. We construct a broad class of nonsingular, static and asymptotically-flat black-hole models with a de Sitter core, sourced by an anisotropic fluid which effectively encodes quantum corrections. These corrections are parametrized by a single length-scale $\ell$, which represents an effective ``quantum hair''. Depending on its value, these models interpolate between two-horizon, one-horizon (extremal) or horizonless objects. By analyzing their thermodynamics, we show that models with $\ell \sim R_\text{S}$ (where $R_\text{S}$ is the classical Schwarzschild radius) are thermodynamically preferred over those with $\ell \ll R_\text{S}$, supporting the relevance of quantum corrections at horizon scales. We show that these super-Planckian corrections can have phenomenological signatures, potentially observable in the near future. We also comment on their evaporation process, arguing that the absence of the classical singularity could also be related to the resolution of the celebrated information paradox.