Weinberg shows support for 3+1 gravitational assymptotic safety

[MTd2]

The link to the video is here:

http://motls.blogspot.com/2009/07/cern-weinberg-about-asymptotic-safety.html

 

[Finbar]

Nice!

 

[Bob_for_short]

Good talk! I like it.

The renormalizations play a crucial role, and I am content to hear him saying that they are just redefinitions of the fundamental constants. It is equivalent to discarding the divergent corrections to the right constants present in the original Lagrangian.

As I promote QFT reformulation where no corrections to the fundamental constants arise, the QFT revival looks even more justified.

 

[marcus]

The link I found was this
http://cdsweb.cern.ch/record/1188567/
to the Cern document server.
It is the same site that has Carlo Rovelli's overview of LQG talk he gave to Strings 2008.
Great site!
I like the dotted line that curves up in the future, that his graph of the projected stock price of QFT. Good news for Martin Reuter, Roberto Percacci, asymptotic safe QG, if it turns out that way.

The paper he highlighted by Codello Percacci Rahmede was one we discussed. It is where they truncated down to 7 dimensions but found that the critical hypersurface was only 3D----only 3 parameters to fix, to get on the attractive hypersurface where the flow will bring you to the UV fixed point.
Several other A.S. papers he talked about were also ones we have flagged as interesting, ones by Bonanno Reuter Sauressig, Benedetti, in various combinations. All the A.S. names we know came out in Weinberg's talk.

It was the only part of the talk where he seemed to get really excited---the idea that string may not be necessary, may not be a part of nature, and that what is needed is "good old quantum field theory" as he put it.
Interesting ideas and, as he said, should be pursued. To get to this part of Weinberg's talk (which is 70 minutes long) you have to drag the button forward to 58 minutes.

The cds link I gave here gives you a somewhat larger screen and it is easy to fast forward to whatever time, like 58 minutes, that you want.
A fascinating and hopeful talk!

BTW Weinberg mentioned that in December 2009 there would be an Asymptotic Safe QG conference at Perimeter Institute. I'd wager dollars to donuts that Weinberg will be on hand for that.

 

[lumidek]

Dear Daniel MTd2, you seem to be confused about some very basic, even sociological and historical points. The reason why Weinberg "shows support" for asymptotic safety, even though he thinks it's unlikely, is that he invented it http://arxiv.org/abs/hep-th/9702027 & his text in General Relativity; an Einstein Centenary Survey.

 

[MTd2]

http://www.math.columbia.edu/~woit/wordpress/?p=2199

"He ended with comments on the “asymptotic safety” approach to quantum gravity, noting that it is quite possible that string theory is not needed, that the world can just be described at a fundamental level by quantum field theory (and thus his conjecture that QFT may come back into fashion as a fundamental theory):

I don’t want to discourage string theorists, but there’s just the possibility that maybe that isn’t the way the world is, that the world is much more like we’ve always known, that is, the Standard Model and General Relativity."

 

[Finbar]

http://www.math.columbia.edu/~woit/wordpress/?p=2199



"I don’t want to discourage string theorists, but there’s just the possibility that maybe that isn’t the way the world is, that the world is much more like we’ve always known, that is, the Standard Model and General Relativity."

Ah like poetry to my ears. Probably a bit optimistic but hey. I think the main point of this talk is that our attitude towords QFT in general should not be set in stone by current trends. It is a theory which we still do not yet fully undestand. String theory is also an important theory and our attitudes to it are also bound to change has we study it deeper and uncover new experimental data.