how reliable are Peter Woit and Lee Smolin?

g.lemaitre

A lot of first-rate physicists praise string theory and I've read that it has quite a lot of promise. However Susskind concedes that "string theory has no shortage of critics who will tell you that it is a monstrous perversion." So I'd like to read some of these critics. The only ones that I know of who have written non-technical books are Woit and Smolin. Amanda Peet, paraphrasing, describes Lee Smolin as incapable of understanding. How reliable are these authors? I want to know before I start reading them.

jedishrfu

Here's a website of critics to string theory

http://www.dummies.com/how-to/conten...-skeptics.html

jedishrfu

You should also read greens books too to compare and contrast string theory

Elegant universe

Fabric of the cosmos

...

g.lemaitre

I got up to about page 100 in the Fabric of the Cosmos. Green rewrites every sentence 3 times. He's way too wordy. He doesn't understand concision. I look his upbeat speaking style, his movie star looks and his enthusiasm but not his prose style.

jedishrfu

True then perhaps michio kaku who is pretty good at explaining things and is a top notch physicist.

g.lemaitre

whoa, penrose, feynman, glashow, krauss - all critics of string theory, i had no idea that was the case.

atyy

Smoline's criticism should be borne in mind with his statement that "it seems that any acceptable quantum theory of gravity, whatever its ultimate formulation, is likely to reduce to a perturbative string theory in the appropriate limit." http://arxiv.org/abs/gr-qc/9508064

marcus

Watch minutes 49-53 of this 2009 talk by Steven Weinberg.
http://www.youtube.com/watch?v=Zl4W3DYTIKw

He says much that is kind about the string program (he's a friend/diplomat and used to do string theory himself in the 1980s) but at the same he is trying to be truthful. It's an interesting moment at the end of very interesting talk (about new physics that could emerge from LHC and the new astrophysics instruments). Thru the whole talk he did not mention superstring. And the first question was from a science journalist who asked why he didn't mention superstring and what did he think about it. So that starts at minute 49. It is a gentle and balanced elderstatesman view (or so it seems to me.)

It was at the Science Writer's conference October 2009 in Austin Texas.

A lot has happened since 2005, when the books you mentioned were written. They came out in 2006, I think. It's not obvious to me that they are relevant now. What you need to know is the trend in new faculty hiring in US and Canada physics departments. It tells you wordlessly what is in the minds of department chairmen and hiring committees. What lines of specialization they think are interesting or that might pay off somehow. No arguments, no rationales, no philosophizing, no animosity, no criticism of the string program, but essentially no jobs.

I don't see that this has anything to do with the books you mentioned and I'm not sure why you would go back and read how the situation was described in 2005. Steven Weinberg's brief remarks, while not actually criticism touch all the bases (lightly) and give you all the pieces of the puzzle (if you want to fit them together.)

I mean no disrespect to Lee Smolin and Peter Woit. Woit's blog is a valuable source of accurately reported current physics news and there is lively discussion. Smolin has done first-rate creative and fundamental work in a variety of theory areas. They are both much more than the "string critics" they are known as in the media.

Actually as criticism I found the quotes on string by Feynman, Krauss, Laughlin, and Anderson to be more pointed, biting, memorable, and on the whole funnier. All that is somewhat dated though, and receding into the past.

g.lemaitre

thank you, for this link.


Your sentence is a bit ambiguous. Are you saying that string theorists are not being hired any more? I find that hard to believe? That sentence could be saying something else.

marcus

I'll get some figures. First-time faculty hires in Particle Theory as a whole and in String as a part of that, by year, in Usa and Canada.

The particle theory job picture for this year (Usa + Canada, first-time faculty positions) is the same as it was 8 June, over a month ago. Twelve HEP theorists have offers, of whom one is a string theorist. Faculty hiring for the fall semester could still change but now seems complete.

Annual first time faculty hires in theoretical particle physics (Usa + Canada)
(Up through 2010, the rates are averaged over 3 years intervals.)
The source used for the preliminary 2012 estimates: http://particle.physics.ucdavis.edu/rumor/doku.php
Source for previous years: http://www.physics.utoronto.ca/~poppitz/Jobs94-08

The point is that in the period 1999-2001 on average HALF the particle theory jobs went to string. Now it is more like 1/10 or 1/12. Again in 1999-2001, the average rate of string hires was about 9 per year.. In 2011 only one string theorist got hired.

In HEP (high energy physics) theory, departments are now going more towards cosmology and non-string particle theory as relates to phenomena that experimentalists can look for. There is also condensed matter theory and atomic physics but those are separate categories.

jedishrfu

another theory of interest

http://plus.maths.org/content/taming-infinity

g.lemaitre

Marcus, how about yourself? what's your job?

Also, I listened to the Weinberg lecture. He said he gave up on super string theory in the last 90's and he's more interested in cosmology now because there is more of the excitement between experiment and theory as there was with HEP in the 60s and 70s. He also said he finds super string theory more attractive but he's working on something else to unify QM and GR. It was a good answer.

audioloop

weiberg is superb,

http://arxiv.org/pdf/1109.6462v4.pdf

..."From the point of view adopted here, there is nothing special about
measurement. Measurement is just a process in which the state vector of a
system (typically microscopic) becomes entangled with the state vector of
a relatively large system, which then undergoes a collapse to an eigenstate
of some operators determined by the characteristics of that system. So we
expect that the state vector of any system undergoes a similar collapse, but
one that is much faster for large systems. But collapse to what? Without
attempting a precise general prescription, we have in mind that these are the
sorts of states familiar in classical physics. For instance, in a Stern-Gerlach
experiment, they would be states in which a macroscopic detector registers
that an atom has a definite trajectory, not a superposition of trajectories.
In Schrodinger’s macabre thought experiment, they are states in which
the cat is alive, or dead, but not a superposition of alive and dead. These
states are like the “pointer states” of Zurek, but here these basis states
are determined by the physics of the assumed collapse of the state vector,
rather than by the decoherence produced by interaction with small external
perturbations"...

g.lemaitre

Well, they are the only non-technical critiques of String Theory that have been written, other than maybe Moffat's Reinventing Gravity: A Physicist Goes Beyond Einstein.

Dickfore

That doesn't mean anything. Old authorities are hard to accept new ideas, even if they are quite original and ingenious. And, finally, the scientific method does not rely on authority.

Lee Smolin, as far as I am aware, is a reliable scientist who devoted his research to a new, and uncharted area in Physics (Loop Quantum Gravity). In doing so, he follows the methods of any theoretical physicist. You must understand, however, that every step is a non-trivial endeavor. Even calculating basic things in String Theory is a hard business. And, if you want to have a prediction, you must calculate. As far as Peter Woit goes, I don't know what his expertise is.

haushofer

But at least you can do calculations, like graviton-graviton scattering. Afaik are these calculations in e.g. Loop Quantum Gravity not possible (but I could be wrong).

marcus

The calculation of n-point functions using the spinfoam dynamics that was worked out in 2008-2010 has been a gradual process.
I think they are pretty much up to level 3 now: computing the 3-point amplitudes to leading order. I would not say "not possible", but it's hard. You assume so little about geometry to start with.
Here's a sample of how this part of the program stood last year:

http://arxiv.org/abs/1105.0566
Euclidean three-point function in loop and perturbative gravity
Carlo Rovelli, Mingyi Zhang
(Submitted on 3 May 2011)
We compute the leading order of the three-point function in loop quantum gravity, using the vertex expansion of the Euclidean version of the new spin foam dynamics, in the region of gamma<1. We find results consistent with Regge calculus in the limit gamma->0 and j->infinity. We also compute the tree-level three-point function of perturbative quantum general relativity in position space, and discuss the possibility of directly comparing the two results.
16 pages

One really should not say that calculation is "not possible". After all the calculations using the theory have been of enormous historical importance to LQG development. It was, for instance, calculation of the graviton 2-point function (the graviton propagator) in 2007 which brought about a completely new formulation of the dynamics (2008-2010).

Calculation of the area and volume operator spectra, to take another example, has formed the basis for the active development we see in Loop cosmology. This has lead to more calculation and numerical simulations coming to grips with the start of expansion, with inflation, and with prediction of observable features in cosmic background radiation. Loop has a lot of engagement with real stuff that is, in fact, based on it's ability to calculate.