QUANTUM ERGOSPHERE EFFECT OF SPHERICALLY SYMMETRIC NON-STATIC BLACK HOLE

The mass-energy formula of black holes implies that up to 50% of the energy can be extracted from a static black hole. Such a result is reexamined using the recently established analytic formulas for the collapse of a shell and the expression for the irreducible mass of a static black hole. It is shown that the efficiency of energy extraction process during the formation of the black hole is linked in an essential way to the gravitational binding energy, the formation of the horizon and the reduction of the kinetic energy of implosion. Here a maximum efficiency of 50% in the extraction of the mass energy is shown to be generally attainable in the collapse of a spherically symmetric shell: surprisingly this result holds as well in the two limiting cases of the Schwarzschild and extreme Reissner–Nordström space–times. Moreover, the analytic expression recently found for the implosion of a spherical shell to an already formed black hole leads to a new exact analytic expression for the energy extraction which results in an efficiency strictly less than 100% for any physical implementable process. There appears to be no incompatibility between General Relativity and Thermodynamics at this classical level.

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Extreme black hole anabasis

Journal of High Energy Physics ◽

10.1007/jhep03(2021)223 ◽

2021 ◽

Vol 2021 (3) ◽

Author(s):

Shahar Hadar ◽

Alexandru Lupsasca ◽

Achilleas P. Porfyriadis

Keyword(s):

Boundary Condition ◽

Black Hole ◽

Spherically Symmetric ◽

Asymptotically Flat ◽

Flat Region ◽

Extreme Black Hole ◽

Condition Change ◽

Birkhoff's Theorem ◽

Birkhoff’S Theorem

Abstract We study the SL(2) transformation properties of spherically symmetric perturbations of the Bertotti-Robinson universe and identify an invariant μ that characterizes the backreaction of these linear solutions. The only backreaction allowed by Birkhoff’s theorem is one that destroys the AdS2× S2 boundary and builds the exterior of an asymptotically flat Reissner-Nordström black hole with $$ Q=M\sqrt{1-\mu /4} $$ Q = M 1 − μ / 4 . We call such backreaction with boundary condition change an anabasis. We show that the addition of linear anabasis perturbations to Bertotti-Robinson may be thought of as a boundary condition that defines a connected AdS2×S2. The connected AdS2 is a nearly-AdS2 with its SL(2) broken appropriately for it to maintain connection to the asymptotically flat region of Reissner-Nordström. We perform a backreaction calculation with matter in the connected AdS2× S2 and show that it correctly captures the dynamics of the asymptotically flat black hole.

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Hawking Radiation from a Non-static Black Hole

Chinese Physics Letters ◽

10.1088/0256-307x/8/10/015 ◽

1991 ◽

Vol 8 (10) ◽

pp. 548-550 ◽

Cited By ~ 48

Author(s):

Zhao Zheng ◽

Dai Xianxin

Keyword(s):

Black Hole ◽

Hawking Radiation ◽

Static Black Hole

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