Breakdown of the semiclassical approximation at the black hole horizon

Esko Keski-Vakkuri, Gilad Lifschytz, Samir D. Mathur, Miguel Ortiz

Research output: Contribution to journalArticlepeer-review


The definition of matter states on spacelike hypersurfaces of a (1+1)-dimensional black hole spacetime is considered. The effect of small quantum fluctuations of the mass of the black hole due to the quantum nature of the infalling matter is taken into account. It is then shown that the usual approximation of treating the gravitational field as a classical background on which matter is quantized breaks down near the black hole horizon. Specifically, on any hypersurface that captures both infalling matter near the horizon and Hawking radiation, quantum fluctuations in the background geometry become important, and a semiclassical calculation is inconsistent. An estimate of the size of correlations between the matter and gravity states shows that they are so strong that a fluctuation in the black hole mass of order ePlanck-M/M produces a macroscopic change in the matter state.

Original languageEnglish
Pages (from-to)1764-1780
Number of pages17
JournalPhysical review D
Issue number4
StatePublished - 1995
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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