Iosif Bena: black hole microstates

Iosif Bena was so nice to give us a special, informal talk about black hole and black ring microstates. If you combine black holes and black rings, you can obtain black Saturns as Henriette Elvang et al. call it, but Bena et al. don't want to combine them in the same configuration. ;-)

There has been some tension between Harvard led by Andy on one side and Iosif, apparently representing the consensus of 90% of the rest of the world ;-), on the other side concerning the meaning of the word "microstate" etc.

A state is a wavefunction (or wave functional) on the configuration space of your theory, not a classical configuration as the consensus seems to think. ;-)

Iosif uses the word "microstate" for particular classical configurations which is hard to digest. But if you remove the controversial terminology from his message and if you try to make sense out of what he said, the result is that they can apparently construct stationary spherically asymmetric solutions of the supergravity equations that look like the D1-D5-P and similar black holes almost everywhere outside the region where you would normally expect an event horizon. These solutions are supported by fluxes and they have bubbles in them. The fluxes are adjusted to make the configuration completely smooth, as you can check by a change of coordinates. These solutions may be viewed as uplifts of Denef's solutions. See e.g. Werner+Bena

• hep-th/0701216
  

They can also calculate the redshift at the point where the bubbles start, translate it into a mass gap via the AdS/CFT dictionary to see that it agrees with the mass gap of some string states on the CFT side, and they argue that their "states" (classical configurations) should thus be generic and account for all of the black hole entropy. I think that it is fair to say that no one at Harvard understands these arguments, to use a polite language.




Why do they think that their list of degrees of freedom used for their supergravity solutions is complete? The Schwarzschild solution is also a generic solution that looks like a neutral black hole everywhere outside the event horizon: does it mean that the (zero-dimensional) space of such solutions has a volume that corresponds to the exponentiated entropy?

At any rate, we have already mentioned Samir Mathur's picture that these solutions don't contradict the no-hair theorems because several conditions of the no-hair theorem are not satisfied here. This framework would give a completely new picture of physics inside the black holes. For example, you would probably get killed as soon as you would approach the former horizon.