## Monday, February 22, 2010

### Jan de Boer: pop talk on holography

Jan de Boer is an extremely serious - and a highly technical - physicist who arguably belongs to the top 10 people in the world who study and understand the quantum structure of black holes (and their microstates) in quantum gravity. See e.g. Supergravity can't be the whole story and Black holes: quantum mechanics at microscopic distances.

But because he was invited to Nordita and Nordita, while having been found by Niels Bohr, has a very limited world-quality research into quantum gravity these these days (and the knowledge gap below their Troels and Larus is pretty large), he prepared a 67-minute popular talk on quantum gravity and holography - and an excellent one (at least if you're ready for a package of the Dutch accent). See:
Holography, quantum gravity and black holes (click)
The streaming video link is at the bottom of the page above and you may need RealPlayer. The talk starts with some really simple, PBS-level statements about physics but it gets more interesting and nontrivial later.

Around 20:00, you already hear lots of things about the thermodynamics of black holes, a topic that began as an analogy. It continues with the black hole entropy, AdS/CFT, low-viscosity liquids in AdS/QCD, phase diagrams in superconductors, and I am convinced that most readers will learn new things from the talk. I still find it amazing how much progress in quantum gravity could have been made just in 15 years or so.

Jan's funny punch line is that when you fall into a black hole, you feel like after having drunk 11 pints of beer (not sure whether Dutch or Czech beer): you're slowly losing your consciousness. Well, I am not sure whether I understand the details of his analogy. This loss of consciousness should better not occur before the local physics deduced from (semi)classical GR indicates that everything seems to be "normal" - like low temperature.

So I actually do believe that it's inevitable that the averaging over the black hole microstates - because they're linked to very high frequency and wave-number patterns - has to preserve the perception of a normal empty space up to the very close vicinity of the singularity, for all reasonable low-energy probes, and that all the non-local stuff may only be detectable by some very special probes (that probably can't exist in practice).

Questions wanted to clarify Jan's statements about the need for additional experimental evidence for string theory, and asked whether the low-viscosity fluids were superfluids. They were not but Jan didn't manage to explain why the superfluids don't violate the universal bounds (they also have a low entropy density).

Via "Interna", a blog post at a Western European physics blog.