## Thursday, January 30, 2014

### Gravitational Collapse and the Horizon

It has been suggested [1] that the resolution of the information paradox for evaporating black holes is that the holes are surrounded by firewalls, bolts of outgoing radiation that would destroy any infalling observer. Such firewalls would break the CPT invariance of quantum gravity and seem to be ruled out on other grounds. A different resolution of the paradox is proposed, namely that gravitational collapse produces apparent horizons but no event horizons behind which information is lost. This proposal is supported by ADS-CFT and is the only resolution of the paradox compatible with CPT. The collapse to form a black hole will in general be chaotic and the dual CFT on the boundary of ADS will be turbulent. Thus, like weather forecasting on Earth, information will effectively be lost, although there would be no loss of unitarity. See: Information Preservation and Weather Forecasting for Black Holes

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${r}_{0}=\frac{GM}{{c}^{2}}$
The critical radius ${r}_{0}$ where the energy of $m$ changes sign is called the horizon radius. The region inside this critical radius is called a black hole. See: Can we make objects of zero mass?
Implications for the black hole problem:Recall that vacuum fluctuations near the horizon had lead to the creation of particle pairs See: The Black Hole Information Paradox
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Ahmed Almheiri, Donald Marolf, Joseph Polchinski, James Sully
We argue that the following three statements cannot all be true: (i) Hawking radiation is in a pure state, (ii) the information carried by the radiation is emitted from the region near the horizon, with low energy effective field theory valid beyond some microscopic distance from the horizon, and (iii) the infalling observer encounters nothing unusual at the horizon. Perhaps the most conservative resolution is that the infalling observer burns up at the horizon. Alternatives would seem to require novel dynamics that nevertheless cause notable violations of semiclassical physics at macroscopic distances from the horizon. Black Hole: Complementarity vs Firewall