After reading Harlow's review notes on the black hole information problem, I am convinced that there could be many ways to explain the black holes information problem and black holes interior. It would be worth waiting and seeing which one is correct and which is less accurate. Here, I want to collect those possible ways of describing BHs.
- Old Hawking Radiation: This was the idea of Hawking where he used Bekenstein entropy and implied negatively about unitarity, which later Hawking graciously accepted.
- Complimentarity: This is a set of progressive ideas, mainly based on unitarity, purity of Hawking radiation, Einstein equivalence, and low energy EFTs. This one has exciting works from Hayden, Preskill, and Susskind.
- AMPS: This one was put forward by Almheiri, Marolf, Polchinski, and Sully in this paper. This says that four things assumed (or used as concrete builds) in complementarity cannot all be true. They propose a firewall that would incinerate information. One can say a firewall is just an extended singularity or horizon. The firewall appears to break the Einstein equivalence principle which states that any observer should not see anything unusual at horizon.
- Fuzzballs: This is for big charged black holes where one gets fuzzball-like solutions. However, hard to find such fuzzballs in uncharged black holes.
There are a few more (of which I am not now fully aware), including the Raju-Papadodimas theory and Horowitz and Maldacena theory. It is interesting to observe that some ideas clash with others, and some just sound crazy out the well, which should only be taken with a grain of salt unless there are concrete understanding of things.
