A Model of Black Hole Evaporation and 4D Weyl Anomaly

Abstract

Abstract:We analyze the time evolution of a spherically-symmetric collapsing matter from the point of view that black holes evaporate by nature. We consider conformal matters and solve the semi-classical Einstein equation G µν = 8πG T µν by using the four-dimensional Weyl anomaly with a large c coefficient. Here, T µν contains the contribution from both the collapsing matter and Hawking radiation. The solution indicates that the collapsing matter forms a dense object and evaporates without horizon or singularity, and it has a surface, but looks like an ordinary black hole from the outside. Any object we recognize as a black hole should be such an object.

On the near-horizon geometry of an evaporating black hole

“…For instance, the black-hole models considered in refs. [14]- [18,26,27] demonstrate a different nature.…”

Tests for the existence of black holes through gravitational wave echoes

“…In summary, with the exception of boson stars, we do not know how or if UCOs and ClePhOs form in realistic collapse or merger scenarios. [37,116] (but see [117]) [23,24] 2 − 2 holes ClePhOs ∼ [118] (but see [118]) (but see [118]) [23,24] Collapsed ClePhOs ∼ polymers [119,120] (but see [119,121]) [121] Quantum bounces / ECO -ClePhOs ∼ black stars [7,8,[122][123][124][125] (but see [123,126]) [125] Quantum stars * Table 1: Catalogue of some proposed horizonless compact objects. A tick means that the topic was addressed.…”

“…At these CM energies, it is possible that new degrees of freedom are excited (some of which might even be the unknown physics that forms these compact objects in the first place). It is well possible that if new fields exist they carry a substantial fraction of the luminosity (while going undetected in our telescopes) 8 . Even without advocating new physics beyond the 10 TeV scale, extrapolation of known hadronic interactions to large energies suggests that about 20% of the collision energy goes into neutrinos, whose total energy is a sizeable fraction of that of the photons emitted in the process [151].…”

“…Therefore, any argument suggesting that exotic compact objects are excluded for any has to be taken with great care. 8 Incidentally, gravitational radiation makes only negligible contribution to the total flux, even for such large CM energies. The ratio of EM to gravitational radiation generated during these processes was estimated to be [150] …”

“…The resolution of such problems could include changing the endstate of collapse [4][5][6][7][8] (perhaps as-yet-unknown physics can prevent the formation of horizons), or altering drastically the near-horizon region [9]. The fact of the matter is that there is no tested nor fully satisfactory theory of quantum gravity, in much the same way that one did not have a quantum theory of point particles at the beginning of the 20th century.…”