Horizon-Brightened Acceleration Radiation and Optical Signatures of Generic Regular Black Holes from Nonlinear Electrodynamics

Abstract

We investigate horizon-brightened acceleration radiation (HBAR) and optical signatures for a broad class of regular black holes sourced by nonlinear electrodynamics. The spacetimes considered are static, spherically symmetric, and nonsingular, and they include Bardeen-like, and Hayward-like regular black-hole limits as spacial cases. We characterize the horizon structure and thermodynamics properties, and we compute key optical observables by determining the photon-sphere location and the corresponding shadow size as seen by distant observers, including controlled perturbative limits and full numerical solutions. Using angular-size constraints for SgrA* and M87* from the Event Horizon Telescope and the GRAVITY collaboration, we perform a Markov Chain Monte Carlo analysis to infer the admissible parameter ranges of the model and to quantify degeneracies among the black-hole mass and nonlinear-electrodynimcs parameters. On the quantum side, we develop the near-horizon reduction relevant for HBAR, showing that the dominant sector governing the detector response exhibits conformal behavior and leads to a thermal excitation spectrum governed by the horizon temperature. We formulate a Lindblad master-equation description of the radiation field, identify the thermal steady state, and derive an HBAR entropy-energy relation consistent with a Clausius-type first law. Finally, we establish a Wien-type displacement law for the HBAR spectrum, expressing the peak wavelength in terms of the horizon thermodynamics, thereby providing an additional observable link between nonlinear electrodynamics, regularity, and near-horizon quantum radiation.

Figures (10)

• Figure 1: Schematic illustration of horizon-brightened acceleration radiation (HBAR): a dilute atomic cloud falls toward a black hole; a near-horizon mirror suppresses background emission, and atom–field interactions produce acceleration radiation. Inset: effective two-level transition with photon emission Scully2018.
• Figure 2: Dependence of the horizon radius $r_g$ (left panel) and Hawking temperature $T_H$ (right panel) on magnetic charge $q_m$ for different solutions.
• Figure 3: Dependence of the photon radius $r_{ph}$ on dimensionless magnetic charge $Q=\frac{q_m}{M}$ for different solutions.
• Figure 4: The shadow image for different cases
• Figure 5: MCMC for Sgr A* from EHT (left) and from gravity (right). M87 bottom