Conformalons: a new class of black hole mimickers
Abstract
Abstract In any conformally invariant gravitational theory, the space of exact solutions is greatly enlarged. Therefore, we cannot exclude the Weyl’s conformal invariance to be spontaneously broken to spherically symmetric vacuum solutions that exclude the spacetime region inside the black hole’s event horizon from our Universe. We baptize these solutions conformalons . It turns out that for all such spacetimes nothing can reach the Schwarzschild event horizon in a finite amount of proper time for conformally coupled “massive” particles, or finite values of the affine parameter for massless particles. Therefore, for such vacuum solutions the surface $$r = 2 M$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>r</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2</mml:mn> <mml:mi>M</mml:mi> </mml:mrow> </mml:math> becomes an asymptotic region of the Universe. As a general feature, all conformalons show a gravitational blueshift instead of a gravitational redshift at the unattainable Schwarzschild event horizon, hence avoiding the Trans-Planckian problem in the Hawking evaporation process. Unexpectedly, the Hawking’s temperature of the conformalons turns out to be negative and the thermodynamic interpretation leads us to speculate about a possible maximum energy state of the Hawking radiation. Contrary to the Schwarzschild spacetime, for the conformalons the gravitational collapse consists of matter that falls down forever towards the Schwarzschild horizon without ever reaching it. Hence, the annihilation process between the matter and Hawking’s negative energy particles takes place outside the surface at $$r = 2 M$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>r</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2</mml:mn> <mml:mi>M</mml:mi> </mml:mrow> </mml:math> . Finally, the information is not lost in the whole process of singularity-free collapse and evaporation.