Fuzzballs, Firewalls and all that

Abstract

Some 40 years ago Hawking showed that if the black hole has a smooth horizon, then information will be lost when the black hole radiates. In string theory black holes appear to have a complete set of `hair'; these black hole states are called fuzzballs, and they radiate like normal bodies with no information loss. It was recently argued that structure at the horizon will necessarily feel like a `firewall' to an infalling observer. We will show that this need not be the case, since one can have `fuzzball complementarity' where an approximately smooth horizon appears as a `dual' description.