Wednesday, October 31, 2007 ... Deutsch/Español/Related posts from blogosphere

David Gross: The coming revolutions in fundamental physics

A similar talk by Gross: Stringfest in Israel

Separate page...

The video of the lecture from 10/19/2007 at UC Berkeley where he studied is 98 minutes long. The woman who introduces him says that he was awarded a nice award: Gross became one of 800 students who were arrested in 1964 for the free speech movement's Sproul Hall sit-in.

Frances Hellman, the boss of physics at UC Berkeley, thinks that it is the most important achievement of Gross's. Incidentally, I can't resist to point out a sad fact that Hellman's recent article was an anti-Summers rant in Science back in 2005 written with roughly 100 feminist co-authors.

Gross begins to speak at 3:40.

Cartoons and memories

Gross says that the beginning of his physics life was more important for him at Berkeley than some other events at the same school. He shows his favorite cartoons, including some recent ones that were influenced by two "rather silly books". Gross was depressed by the "Harvey's place" cartoon until someone sent him the "String theory: When physics gets physical" ad that restored his confidence in the American media. ;-)

Particle physics: SM and beyond

He instantly returns to the structure of elementary particles (8:58). Appraisal of the Standard Model is at 13:00. It may work up to the Planck scale. At 17:30, he cherishes the informed ignorance that the Standard Model has produced. Gross asks many "why" questions that became more interesting than 45 years ago. At 20:50, some advances of cosmology are discussed.

At 24:05, the search for unification starts. Gross chooses SO(10) as the nice GUT: good choice. At 33:45, he gets to the LHC and supersymmetry (Zumon's superpartner is in the audience) - his superspace-focused presentation of SUSY is very similar to mine. At 48:20, gravity enters the game. At 51:10, quantum gravity appears for the first time.

Quantum gravity and strings

At 52:30, he explains that we must go from GR to string theory, a (54:54) conservatively radical modification of the principles of physics. Gross argues that you should always modify as little as possible because otherwise, you are pretty much guaranteed to be inconsistent with reality, logic, or both. String theory only changes the building blocks. The mathematics is a bit more complicated but in 100 years, it will be taught at high schools (58:30). ;-)

Nice surprises occur with interactions because all the nasty uncertainty in the singular vertices of Feynman graphs goes away (59:30). Pants diagrams are non-singular, uniform, and create no new parameters, for the first time in physics. At 64:30, he explains the amazing property of string theory that it predicts everything, including the dimensionality of space. And both gauge forces and gravity appear automatically, without being inserted.

More triumphs of string theory

At 66:30, achievements of string theory are summarized: finiteness, incredible uniqueness, richness, the calculable fate of black holes. Gross expects that eventually the string revolution will be on equal footing with relativity or quantum mechanics. At 69:20, he talks about the information loss. String theory saves the day, 70:00. The origin of the Universe, 70:50, remains an open question, together with the right compactification of extra dimensions, right SUSY breaking, and the cosmological constant problem (72:10).

At 73:00, you see the Calabi-Yau manifold from this blog's background. Half a minute later, zillions of non-realistic vacua are mentioned. At 74:30, the vacuum energy is described. At 78:20, the landscape scenario is sketched; at 80:05, Gross unfortunately can't prove that the A-word principle, proposed by his otherwise rational colleagues, is wrong. Dirac faced the same mystery but he was much too Dirac (82:10) to envoke anthropic arguments. Gross explains that the Dirac's Mproton/Mplanck tiny ratio has actually been explained by QCD's log running of alpha from the unification scale. Also, the seesaw mechanism explains the small neutrino masses.

Unknown definition of string theory

At 87:00, we don't know what the basic and full equations of string theory are, only many descriptions. Perhaps ST is like QFT, a framework. But it can't be modified. Maybe something is missing but we don't know what it is. But maybe we need new rules, 88:50. Witten's comment that space and time may be doomed scares some people, 91:20. According to Seiberg, they're illusions - pretty good ones for Gross who has gone much over one of them. Space is emergent, 91:40, but time must thus be as well and we have no idea about timeless physics, 92:40. A summary starts around 93:40, including AdS/CFT (94:35).

We have a wonderful theory but the most exciting questions wait to be answered, exciting new discoveries about our crazy but elegant universe (see below) are behind the corner. End, thank you.

Update about the rate of progress

The author of one of those "rather silly books" comments that a little has changed in these popular talks during the last 3 years. I am amazed by this surprise. Changes that substantially influence popular talks about physics, as opposed to the technical perspective, happen - sometimes gradually - once in 20 years or so and there is nothing unusual about the current rate of changes in comparison with the history of science. Compare the popular talks between 1934 and 1937 - or almost any other 3-year period - and you won't see any significant difference either.

Physics as started by Newton has been around for 350 years and people were trying to understand the world for millenia. These authors of silly books would like to impose absurd deadlines and other sensational criteria upon science, ignoring reality. Just like in catastrophic global warming, the predictions that influence an average citizen and the apocalypse must double every year and new fads should supersede the previous ones at least once a year, they think.

But this mystification, hype, and fashionable excrements are not how real science has ever worked. This is how it works in the skulls of retarded pseudoscientists and charlatans, and I am surely not talking about global warming salesmen, Mr Woit, and Mr Smolin only. Serious science is a conservative enterprise and its philosophical summaries only change very rarely and very subtly. Intellectual diarrhoea - like the production of Lee Smolin's papers - is something very different than science.

And that's the memo.

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snail feedback (1) :

reader Doug said...

Hi Lubos,

Check out this summary report at:
USA Today, ‘New spin on how stars are born’, By Ker Than,
Copyright 2007, Inc. ALL RIGHTS RESERVED.

Original Letter:
Nature 450, 71-73 (1 November 2007) | doi:10.1038/nature06220; Received 8 June 2007;
Accepted 4 September 2007

Antonio Chrysostomou, Philip W Lucas and James H Hough,
‘Circular polarimetry reveals helical magnetic fields in the young stellar object HH 135–136’.

If this Nature Letter is confirmed, then David Hestenes may have great insight into the value of the helix.

I first posted to your blog about the possible importance of the helix 2-3 years ago, You did provide a couple of ArXiv references about the helix. Thanks

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