Roldao da Rocha

We construct a coherent-state quantum extension of gravitational-decoupling (GD) hairy black holes, in which the classical spacetime geometry emerges as the mean-field limit of a finite graviton condensate, while quantum fluctuations provide a natural short-distance regulator. The coherent quantum GD hairy black hole metric is obtained by Gaussian smearing of the gravitational potential, with an effective width encoding the size of the quantum core. The resulting geometry is free of curvature singularities over appropriate parameter ranges and exhibits a modified horizon structure. We also investigate geodesic motion in the coherent quantum GD hairy spacetime and find significant deviations from the classical Reissner–Nordström (RN) geometry. In particular, the photon ring, critical impact parameter, and light deflection are modified by the combined effects of quantum corrections and GD hair, providing potential strong-field tests of deviations from general relativity. Finally, we employ the WKB approximation to show that the coherent quantum GD hairy black hole has a quasinormal mode spectrum that differs from those of both the classical GD hairy and Schwarzschild black holes.

This paper demonstrates that ordinary fermions, interacting via a BF mediator, form a renormalized structure with non-trivial topological properties. We explore the analogy between the renormalized system and a subset of real three-dimensional topological insulators (TIs) in the vicinity of their single Dirac cones. Using the typical magnitude of TI effective velocities and gaps, we constrain model parameters. The topological nature induced by radiative corrections ensures the existence of helical gapless boundary modes, even for massive bulk excitations. We derive an effective low-energy potential for inter quasi-particle interactions that captures finite-size effects in the axial direction and reveals spin-orbit coupling and time-reversal invariance signatures. The equilibrium configuration of the spin-orbit part of the interaction potential induces helical boundary modes. We also investigate the potential and its topological signatures at the transition to the thin-film limit.

A quantum description of hairy black holes within gravitational decoupling (GD) is developed using coherent graviton states. Classical geometry emerges as the mean-field limit of a finite graviton condensate, while quantum fluctuations introduce a short-distance regulator. We construct a coherent quantum GD hairy black hole metric by Gaussian smearing the gravitational potential, with an effective width that encodes the size of the quantum core. The resulting geometry is free of curvature singularities over appropriate parameter ranges and exhibits modified horizon structures. The effective stress-energy tensor is derived, the energy conditions are analyzed, and the Misner-Sharp mass is computed. We investigate geodesics in the coherent quantum GD hairy black hole geometry, with relevant deviations from the RN case. Photon rings, critical impact parameters, and light deflection exhibit measurable strong-field modifications, allowing observational constraints on deviations from general relativity.

Hairy black hole solutions are constructed within quantum-inspired nonlocal quadratic gravity. Nonlocal effects induce Yukawa screening, which shifts the event horizon inward and modifies both the Bekenstein--Hawking entropy and the Hawking temperature, while also renormalizing the chemical potential. Nonlocal corrections also reduce the magnitude of the negative specific heat, making small hairy black holes more stable, with Helmholtz and Gibbs free energies consistent with the absence of first-order phase transitions. The nonlocal spin-2 propagator contains, in addition to the massless graviton, a massive pole with positive residue and positive norm. Consequently, hairy black holes in nonlocal quadratic gravity are free of ghost instabilities at the quadratic and classical levels, in the effective field theory.

Quasinormal modes for bosonic (scalar, electromagnetic, and axial gravitational) and fermionic field perturbations, radiated from black holes that carry quantum gravitational corrections at third order in the curvature to the Schwarzschild solution, are scrutinized from the propagation of analog transonic sound waves across a de Laval nozzle. The thermodynamic variables, the nozzle geometry, the Mach number, and the thrust coefficient are computed as functions of the parameter driving the effective action for quantum gravity containing a dimension-six local operator beyond general relativity. The quasinormal modes for quantum gravitational corrected analog black holes are also determined for higher overtones, yielding a more precise description of the quantum-corrected ringdown process and the gravitational waveform way before the fundamental mode sets in.