Hawking radiation as perceived by different observers

L C Barbado (1) , C Barceló (1) , L J Garay (2, 3)

1 IAA - Instituto de Astrofísica de Andalucía
2 Departamento de Física Teórica II
3 Instituto de Estructura de la Materia

We use a method recently introduced in Barceló et al, 10.1103/Phys- RevD.83.041501, to analyse Hawking radiation in a Schwarzschild black hole as perceived by different observers in the system. The method is based on the introduction of an " effective temperature " function that varies with time. First we introduce a nonstationary vacuum state for a quantum scalar field, which interpolates between the Boulware vacuum state at early times and the Unruh vacuum state at late times. In this way we mimic the process of switching on Hawking radiation in realistic collapse scenarios. Then, we analyse this vacuum state from the perspective of static observers at different radial positions, observers undergoing a free-fall trajectory from infinity, and observers standing at rest at a radial distance and then released to fall freely towards the horizon. The physical image that emerges from these analyses is rather rich and compelling. Among many other results, we find that generic freely-falling observes do not perceive vacuum when crossing the horizon, but an effective temperature a few times larger than the one that they perceived when started to free-fall. We explain this phenomenon as due to a diverging Doppler effect at horizon crossing.

Mots clés: Black Holes; Hawking Radiation; quantum field theory in curved spacetime; vacuum states

Domaines: Relativité Générale et Cosmologie Quantique [gr-qc]

L C Barbado, C Barceló, L J Garay. Hawking radiation as perceived by different observers. Classical and Quantum Gravity, 2011, 10 (12), pp.125021. ⟨10.1088/0264-9381/28/12/125021⟩. ⟨hal-00710459⟩