Berthiere, Clément; Sarkar, Debajyoti; Solodukhin, Sergey N. (2018). The fate of black hole horizons in semiclassical gravity. Physics letters. B, 786, pp. 2127. Elsevier 10.1016/j.physletb.2018.09.027

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The presence of a horizon is the principal marker for black holes as they appear in the classical theory of gravity. In General Relativity (GR), horizons have several defining properties. First, there exists a static spherically symmetric solution to vacuum Einstein equations which possesses a horizon defined as a nullsurface on which the timelike Killing vector becomes null. Second, in GR, acodimension two sphere of minimal area is necessarily a horizon. On a quantum level, the classical gravitational action is supplemented by the quantum effective action obtained by integrating out the quantum fields propagating on a classical background. In this note we consider the case when the quantum fields are conformal and perform a certain nonperturbative analysis of the semiclassical equations obtained by varying the complete gravitational action. We show that, for these equations, both of the above aspects do not hold. More precisely, we prove that i)astatic spherically symmetric metric that would describe a horizon with a finite Hawking temperature is, generically, nota solution; ii)aminimal 2sphere is nota horizon but a tiny throat of a wormhole. We find certain bounds on the norm of the Killing vector at the throat and show that it is, while nonzero, an exponentially small function of the Bekenstein–Hawking (BH) entropy of the classical black hole. We also find that the possible temperature of the semiclassical geometry is exponentially small for large black holes. These findings suggest that a black hole in the classical theory can be viewed as a certain (singular) limit of the semiclassical wormhole geometry. We discuss the possible implications of our results.
Item Type: 
Journal Article (Original Article) 

Division/Institute: 
08 Faculty of Science > Institute of Theoretical Physics 
UniBE Contributor: 
Sarkar, Debajyoti 
Subjects: 
500 Science > 530 Physics 
ISSN: 
03702693 
Publisher: 
Elsevier 
Language: 
English 
Submitter: 
Esther Fiechter 
Date Deposited: 
28 Dec 2018 14:25 
Last Modified: 
31 Oct 2019 17:58 
Publisher DOI: 
10.1016/j.physletb.2018.09.027 
ArXiv ID: 
1712.09914 
BORIS DOI: 
10.7892/boris.122143 
URI: 
https://boris.unibe.ch/id/eprint/122143 