Thursday, 14 June 2007

Nima's Horizons


Nima Arkani-Hamed is yet another soul that has fallen to the spell of the landscape. Landscape is a perfect framework for predicting things we already know. Nima is a bit more clever than that. He is concerned with a bigger picture. I mean, with conceptual questions associated with the existence of multiple vacua in a gravity theory.

Nima shared some remarks on the subject yesterday in a theory seminar. He drew an analogy between the present situation in particle physics and the early days of quantum mechanics. In the latter case, quantum effects turned out to imply loss of predictivity concerning the results of individual measurements. Now, he believes, we should again accept certain loss of predictivity due to the landscape and the anthropic selection.

That was an introduction. The bulk of the talk was about the Standard Model landscape. It turns out that the landscape pops up in the minimal Standard Model coupled to Einstein gravity with a small cosmological constant. Such a system has, of course, a unique 4D de Sitter vacuum, but there exist many more vacua with compactified spatial dimensions. One example is the class of vacua with the AdS3xS1 geometry. The radius of the circle is stabilized by the interplay of the small cosmological constant and the Casimir energy induced by the photon, the graviton and the light neutrinos. The funny accident is that these vacua would not exist if the cosmological constant were a factor of 10 larger or if the solar neutrino mass squared difference were a factor of 10 smaller.

Nima went on discussing some more technical details of this setup:
  • A near-moduli space of the photon Wilson line wrapping the circle.
  • Black string solutions interpolating between 4D and 3D vacua.
  • The two-dimensional CFT dual to the Standard Model.
All that you can find in his recent paper.

Up to this point, i've been almost fair. Now it's time for a few snide remarks. Listening to this talk was like visiting a flea market. It was colourful and entertaining, but most of the things on display seemed utterly useless. Nima forgot to say what can the Standard Model landscape teach us about the big questions he had addressed at the beginning. Well, certainly the landscape may be present in far simpler setups than string theory. But in this very example it seems totally irrelevant, both from the theoretical and the experimental points of view. I had this guilty feeling that i wouldn't even bother to listen if the name of the speaker were different. Judging from the looks on the others' faces, i wasn't all alone...

Transparencies not available, as usual, though this time it isn't so much of a waste.

6 comments:

a quantum diaries survivor said...

Yes, I believe we need these kinds of speculations as much as we need a cut on HEP budget.

Cheers,
T.

Chris Oakley said...

This guy really ought to get an honest job. Flying around the world peddling bullshit only demeans the subject. If you were in charge of the HEP budget would you fund the Anthropic Landscape? I know I wouldn't. Why should be taxpaying public be any different?

Anonymous said...

You got comments also on the embarrassing talk he gave to the experimentalists?

Jester said...

I'm planning to write a separate post about it. But...the Marmoset paper is 101 pages long. It may take some time...

Anonymous said...

The idea is you spread enough bullshit around the world, then you get to harvest whatever mushrooms pop up. It can be pretty lucrative.

aaacss said...

There is something deeper here. LHC will probably point the way, but we must keep our minds open to new possibilities. There may exist additional dimensions of space and/or time. There may be a simple underlying GUT theory that will only be understood when a different approach is taken. Just because someone isn't trying to figure out the mass of the Higgs doesn't mean their ideas are useless. In the end, I suspect someone's crazy idea will solve this little riddle.