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Fusco, Danny

University of British Columbia

In the Nariai limit of the Schwarzschild-de Sitter spacetime, the black hole horizon and cosmological horizon merge into a single, degenerate horizon. To investigate the stability of this degenerate horizon, we calculate the renormalized stress-energy tensor for the (1+1)D Nariai limit with a scalar field in a symmetric spherical collapse scenario. We do so by making use of a semi-classical one-loop effective action formalism, with a quantized field on a classical curved spacetime background. This formalism lets us compute the stress-energy tensor in curved spacetimes in terms of a known Minkowski result. In doing so, we show that if the Nariai limit does form, then the semi-classical RSET does not, on its own, indicate an instability of the degenerate horizon. We also show that there is a firewall on the outer side of the horizon. These results hinge on the formation of the degenerate horizon via gravitational collapse. However we use our results to make the inference that, during formation of the degenerate horizon, the cosmological horizon might be strongly repelled from the forming black hole due to an infinite negative energy-density. This would prevent the merging of the black hole and cosmological horizons, and presents the possibility that the Nariai limit cannot form via gravitational collapse. If it does form, then it might not be because of two horizons colliding.

Text

2024-04-22

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87921

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/