Sunday, October 08, 2006

Stephen Hawking visited CERN



On the picture, he appears with the director of CERN. Click the picture to get an article. Hawking says that there are three candidates that can be found at the LHC: superpartners, black holes, and the Higgs.

Well, the Higgs should better be found. Finding superpartners is relatively likely but far from guaranteed. The Hindustan Times had an optimistic article yesterday about the search for SUSY.

Finding black holes is a speculative possibility. If that happened, in a Randall-Sundrum-like low-energy gravity scenario, it is very reasonable to assume that these black holes would be evaporating instantly. Such an unlikely discovery would represent an opportunity for several big physics celebrations and awards. Perhaps, Stephen Hawking - perhaps naturally with Jacob Bekenstein - should be the first ones for the prediction of black hole thermodynamics and evaporation.

Hawking gave two lectures about the origin of the Universe:

The semiclassical, technical talk based on a paper with Hertog starts with the strong energy condition, bouncing Universe, compactification on a 6 or 7-dimensional hidden manifold, a picture of such a manifold. Then it says that the potential is a function of the moduli space, shows a picture of the landscape, and identifies the minima as possible vacua of string/M-theory. He continues with 101 in eternal inflation, no-boundary amplitude, and compares the amplitudes for empty and inflating Universe. Finally, he ends up with a perfect agreement of theory with WMAP data, stages of inflation, and conclusions:

  1. The Universe is always in the 4-dimensional semiclassical general relativity regime
  2. The whole Universe is in a homogeneous landscape, not a mosaic
  3. No primordial topological defects
  4. Amplitudes will be non-zero for some, but not all, landscape states

These conclusions definitely seem to have some sauce and power in them even though it is less clear how they follow from the theory. But indeed, it seems that the spacetime must be factorized already during inflation, otherwise the WMAP predictions would have to show discrepancies. It is also clear to me that the amplitudes for some bad, high-vacuum-energy vacua will be negligible, disproving the ideas that every single vacuum must be treated equally.

On the other hand, Hawking claims that to some extent, the anthropic principle is unavoidable even with the no-boundary proposal.

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