Spontaneous excitation of an atom in a Kerr spacetime

Abstract

We consider radiative processes of an atom in a rotating black-hole background. We assume the atom, represented by a hypothetical two-level system, is coupled via a monopole interaction with a massless quantum scalar field prepared in each one of the usual physical vacuum states of interest. We constrain ourselves to two different states of motion for the atom, namely a static situation in which the atom is placed at a fixed radial distance, and also the case in which it has a stationary motion but with zero angular momentum. We study the structure of the rate of variation of the atomic energy. The intention is to clarify in a quantitative way the effect of the distinguished contributions of vacuum fluctuations and radiation reaction on spontaneous excitation and on spontaneous emission of atoms. In particular, we are interested in the comprehension of the combined action of the different physical processes underlying the Hawking effect in the scenario of rotating black holes as well as the Unruh-Starobinskii effect. We demonstrate that, in the case of static atoms, spontaneous excitation is also connected with the Unruh-Starobinskii effect, but only in the case of the quantum field prepared in the Frolov-Thorne vacuum state. In addition, we show that, in the ZAMOs perspective, the Boulware vacuum state contains an outward flux of particles as a consequence of the black-hole superradiance. The possible relevance of the findings in the present work is discussed.

Entanglement dynamics in a Kerr spacetime

“…In turn, as demonstrated in Ref. [23], the Frolov-Thorne vacuum state can describe black-hole superradiance in the quantum regime.…”

“…(20) and the interpretation given in Ref. [23], one can easily understand the origin of such an adversity: This is clearly a consequence of superradiance. In this case the black hole induces stimulated emission.…”

“…One can express such functions with the help of the Hadamard function and the Pauli-Jordan function since Such functions were presented in Ref. [23]. We reproduce them here for convenience.…”

Transition processes of a static multilevel atom in the cosmic string spacetime with a conducting plane boundary

“…As the DDC formalism have been employed in some previous works 10–21 , we immediately obtain the general expression of vacuum fluctuations and radiation reaction contributions to the rate of change of the atomic energy,where 〈⋅⋅⋅〉 = 〈0, b |⋅⋅⋅|0, b 〉. In fact, the above expressions are obtained in a perturbation treatment to order e 2 and we have assumed that the field is initially in the vacuum state |0〉 and the atom is prepared in an arbitrary stationary state | b 〉.…”

“…Later, this formalism was widely utilized to investigate the radiative properties of an inertial or accelerated atom in interaction with a variety of quantum fields in an unbounded flat spacetime 10–14 . Recently, these surveys have been popularized to the curved spacetime background 15–21 . It is worth mentioning that those surveys for atoms in the accelerated or curved background have theoretically predicted the spontaneous excitation process.…”