Acceleration Radiation of Freely Falling Atoms: Nonlinear Electrodynamic Effects

TL;DR

This paper studies the acceleration radiation emitted by freely falling atoms near a Bardeen black hole, revealing a Planckian spectrum influenced by the black hole's parameters and demonstrating suppression near extremality.

Contribution

It extends the quantum-optics approach to acceleration radiation to Bardeen black holes, deriving the spectrum and analyzing effects of the regular core parameter.

Findings

Radiation spectrum is Planckian with temperature set by Bardeen Hawking temperature.

Excitation probability decreases as the black hole approaches extremality.

The regular core parameter modulates the strength of the acceleration radiation.

Abstract

Motivated by the work of Scully \textit{et al.} [ \textcolor{blue}{Proc. Nat. Acad. Sci. 115, 8131 (2018)}] and Camblong \textit{et al.}[ \textcolor{blue}{Phys. Rev. D 102, 085010 (2020)}], we investigate horizon-brightened acceleration radiation (HBAR) for freely falling two-level atoms in the geometry of a Bardeen regular black hole. Building on the quantum-optics approach to acceleration radiation and its near-horizon conformal quantum mechanics (CQM) structure, we show that the dominant physics is again governed by an inverse-square potential in the radial Klein-Gordon equation, with an effective coupling fixed by the Bardeen surface gravity. Using geodesic expansions and a near-horizon CQM reduction of the scalar field, we derive the excitation probability for atoms falling through a Boulware-like vacuum in the presence of a stretched-horizon mirror. The resulting spectrum is Planckian in the mode frequency, with a temperature determined by the Bardeen Hawking temperature. We analyze how the regular core parameter controls the strength of the radiation and demonstrate that the excitation probability is strongly suppressed as the geometry approaches the extremal (cold remnant) limit. Numerical results illustrate the dependence of the spectrum on the Bardeen parameter and on the atomic transition frequency.