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The vacuum polarization around an axionic stringy black hole

A. Carlini·A. Treves·F. Fucito·M. Martellini
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Abstract

We consider the effect of vacuum polarization around the horizon of a 4 dimensional axionic stringy black hole. In the extreme degenerate limit ($Q_a=M$), the lower limit on the black hole mass for avoiding the polarization of the surrounding medium is $M\gg (10^{-15}÷10^{-11})m_p$ ($m_p$ is the proton mass), according to the assumed value of the axion mass ($m_a\simeq (10^{-3}÷10^{-6})~eV$). In this case, there are no upper bounds on the mass due to the absence of the thermal radiation by the black hole. In the nondegenerate (classically unstable) limit ($Q_a<M$), the black hole always polarizes the surrounding vacuum, unless the effective cosmological constant of the effective stringy action diverges.

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A. Carlini, A. Treves, F. Fucito, M. Martellini. 1992-07-16. The vacuum polarization around an axionic stringy black hole. https://doi.org/10.1016/0370-2693(92)91070-p

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