Quantum Black Holes in the Sky?

We propose that a large Schwarzschild black hole (BH) is a bound state of highly excited, long, closed strings just above the Hagedorn temperature. The effective free-energy density is expressed as a function of its entropy density and contains only linear and quadratic terms, in analogy with that of collapsed living polymers. Classically, the horizon of such BH’s is completely opaque, hiding any clues about the state and very existence of its interior.

Event horizons are the defining feature of classical black holes. They are the key ingredient of the information loss paradox which, as paradoxes in quantum foundations, is built on a combination of predictions of quantum theory and counterfactual classical features. Within the semi-classical theory we investigate the possibility that black hole radiation still does not allow for a finite time crossing of the Schwarzschild radius of collapsing matter as seen by distant observers.