Every year around this time the Edge web-site posts responses from a large number of scientists to some particular question. This year the question is “What have you changed your mind about? Why?”, and the results should be posted tomorrow. John Baez has posted his answer here. He writes that he changed his mind about the question of whether he should be thinking about quantum gravity after he realized “the more work we did, the more I realized I didn’t know what questions we should be asking!”, and compares the effort to “throwing darts in a darkened room and hoping to hit the bull’s-eye.” Since changing his mind he has been working on other things, and feels that as a result “I’m making more real progress understanding the universe than I ever did before.”

I think I share John’s point of view on this in many ways, even though I’ve never actively worked on a quantum gravity research project. The problem with quantum gravity research has always seemed to me that, since you can’t measure quantum gravitational effects, you’re in great danger of coming up with lots and lots of “quantum gravities”, but unable to ever know which if any of them has anything to do with the real world. This is kind of what has happened with string theory in recent years. One hope has always been that one will find a mathematically uniquely compelling model, but that has yet to happen. To me the best bet has always been that one might understand quantum gravity by unifying it with the standard model, in a compelling way such that the unified theory explains some of the things the standard model leaves unresolved. This hope was also behind much of the original interest in string theory: it wasn’t just a quantum theory of gravity, but also a theory of particle physics that could be tested.

Like John, I think we still have a long ways to go towards understanding at a deep enough level how quantum field theories really work, and how the internal symmetries of particle physics and the space-time symmetries of gravity can be unified into a more fundamental structure. Progress towards this goal may even require new mathematics, and this means there are all sorts of things to think about and work on.

One person who hasn’t changed his mind about some things is Lubos Motl. According to his latest posting, I’m

…a typical incompetent, power-thirsty, active moron of the kind who often destroy whole countries if they get a chance to do it.

The arXiv puts out charts each year showing the number of submissions by category, the ones for 2007 are now available here. Commentary about this here and here. The general trend is that quite a few years ago the number of HEP papers leveled off, as just about all of them were posted on the arXiv. The number of math papers is still growing quickly, it is only recently that posting math preprints to the arXiv has become a widespread practice. While mathematicians probably write papers at a slower rate than physicists, there are a lot more mathematicians than particle physicists.

The end of 2007 has brought one undesirable change. Recently I was down in Princeton, and found out that the University Store, traditionally one of the best places in the world to buy math and physics books, has now gone out of the book-selling business, turning it over the Labyrinth Books. The new Labyrinth store has some math and physics books, but far, far fewer. Maybe they just are getting started, and 2008 will bring better news about this.

This past summer Terry Tomboulis posted a preprint claiming to have a proof of confinement. Recently there has been a note posted on the arXiv by Ito and Seiler claiming to have found a problem with his proof, and a response from him claiming there is no problem. I’d love to hear from an expert who has taken the time to follow these arguments carefully and can explain what is going on here.

For a recent article by Arthur Jaffe surveying the history of rigorous studies of quantum field theory, see here.

Heading off late tomorrow for a 9 day vacation in Paris. Blogging will probably be light to non-existent and it will take me longer to get around to deleting comments. Please don’t feed the trolls.

Best wishes to all for the new year….

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1. Bee says:

Hi Peter,

Thanks for the link. I wish though you had not mentioned that writing of Lubos, it spoiled my day which was so far very nice. I see no point in leaving a comment at his place, so I’ll leave it here. Lubos frequently makes statements where he claims to speak for “everyone in the field”. Being in the field, and knowing a lot of people in the field, I can assure you if Lubos Motl says “everyone in the field” thinks this or that, it is most definitely not the case. Best,

B.

2. Hans says:

When you are in Paris, don’t forget to buy Lubos recent book
http://www4.fnac.com/shelf/article.aspx?PRID=2062733

L’équation Bogdanov
* Lubos Motl
* Essai (broché)

Article en pré-commande, livraison prévue à partir du 17 janvier 2008

3. Shantanu says:

Peter, did you see the slides of the Cambridge workshop on inflationary cosmology
at here did you find anything interesting there? Some of the talks did touch upon string theory.

4. Daniel de França MTd2 says:

Hello Peter!

Happy new year! 🙂

Unfortunantely links from your website were banned from LM blog. You must read an annoying message to get into his post.

Best wishes.

5. Peter Woit says:

Bee,

Don’t worry, I think that people are no more likely to believe Lubos when he says that he speaks for “everyone in the field” than when he claims that I have the ability to “destroy whole countries”. Unfortunately he’s not the only delusional string theorist around, but few of them are as far gone as he is.

Hans,

Thanks for reminding me of that. Maybe I’ll even meet up with the Bogdanovs and find out the story behind that book…

Shantanu,

Unfortunately I don’t really have the time now to look at many of those talks. There appear to be some useful summaries of the history and state of the idea of inflation. As for “string cosmology”, I still don’t see how it can possibly lead to a testable prediction, and the few talks about this I looked at there don’t appear to give any promising ideas about how such a prediction might arise.

6. Andy T-S says:

Regarding Motl, I have, in my work, observed a researcher who exhibited paranoiac symptoms similar to those of Motl. Ths self-righteous psychopathic “bad apple” wasted enormous amounts of my co-workers’ time and energy and, eventually induced clinical depression in two individuals.

I have read both your and Lee Smolin’s books, and have followed your blog for about a year. I have also attended several of Dr. Smolin’s talks and audited part of his course on quantum gravity at the Perimeter Institute. My impression is that you both are generally fair and diplomatic critics. (As an example of skilful diplomacy, I observed Dr. Smolin at others’ presentations cloak his criticisms by phrasing them as questions that, taken at face value, imply his own, not the presenter’s, ignorance. This is quite the opposite of Richard Feynman’s supercilious caustic sarcasms, hurled from the front row, that left some presenters in tears.)

Neither you nor Smolin have ever said that research in string theory is totally useless and should therefore be dropped entirely. Unfortunately, this gets drowned out by irrational attacks from some unthinking researchers who feel threatened, and by misinformation in the media.

Hans Selye (the discoverer of how stress induces disease) ascribed his success partly to the fact that he worked well with most of his colleagues without, at the same time, squandering his resources trying to befriend those he called “mad dogs”.

For what it’s worth, my advice is to ignore Motl’s shenanigans in future blogs. I would also remove your link to his site: he doesn’t need your help to prove himself a “mad dog”.

7. King Ray says:

Peter, and everyone,

Happy New Year!

Peter, I hope you have a great time in Paris!

I think John Baez is right, it is hard to make progress in quantum gravity. It is difficult to know where to start. A new paradigm is probably needed, as Kuhn has said. Sometimes it is better to work on something where you can gain some traction for a while, rather than spinning your wheels going nowhere for years.

I think Einstein’s practical experience working in the patent office helped sharpen his mind. String and other theorists could probably also benefit by doing some practical work in physics and engineering for a while. It helps build your physical intuition. Einstein said his patent office work helped him to see quickly to the heart of the problem.

8. Hedge Fund Physics says:

Happy New Year!

On Betting Against Physics Hype in 2008

We’re expecting the LHC to find approximately nothing new, but it could be a lot of fun watching a lot of people claiming that they have the new TOE which the LHC will prove right or wrong.

And we’re upping the ante, and hedging against postmodern groupthink and tenured hypesters by calling them out, and betting them $137 that their claims are false. That would be$137 per claim.

Let’s start with claims made by the esteemed Dr. Kip Thorne who in a recent interview stated, (continued at
http://hedgefundphysics.blogspot.com/ )

9. mitchell porter says:

Have the readers of this blog ever suggested conditions under which they think string theorists would stop working on string theory?

In looking through Jacques Distler’s blog in recent weeks, the most important thing I’ve learned is just that there is no known string vacuum which exactly reproduces the Standard Model (below 1 TeV, or whatever; and I suppose one should throw in the new “cosmological Standard Model” too) – there are just a few large classes of qualitatively realistic vacua. Jacques recently completed his proof that you can’t fit the Standard Model into E8; one can imagine a similar, case-by-case proof for string theory (though it would have to be considerably more complicated). But so long as there are several potentially viable approaches, of course they’ll keep at it.

10. layman says:

wow, princeton bookstore now sucks. I visited it around 20 yrs ago and i couldnt leave. Too bad. I was gearing up 2 go there again.

11. Roger says:

With respect to the question of what scientists have changed their mind about this year my answers would be the ILC and science communication.

I’ve come to see the ILC (at this point) as the experimentalists’ string theory. Far too much effort has been sunk into it and too many reports have been published based on detector and Monte Carlo simulations, which are themselves largely based on speculative theories of beyond-the-standard model physics and expectations of what we may see at an, as yet, uncommissioned accelerator. The recent funding cuts are, to an extend, our political masters seeing the emperor has no new clothes (or possibly no new particles). Over the past few years whilst effort has been thrown into the ILC we’ve had a number of excellent facilities online which could have more profitably exploited much of the ILC’s funding- Babar, HERA etc. Having worked on HERA I found the gradual loss of manpower to be very regrettable, especially since there are still many useful measurements to be made, which may now never take place. I’m not against the ILC but, in the UK at least, the rush to sink so much money into the project was IMO ill-advised, especially in light of the recent decision to throw that investment away and pull out.

On a related theme, I used to think that particle physicists were good at communicating the results of their research and the need for support for their field to the power brokers and the general public. It appears that we need something of a rethink in this area (in some countries at least), especially if results from the LHC are further delayed or turn out to be simply unexciting.

12. I guess that not knowing the right questions to ask is precisely what makes quantum gravity attractive to some people, and discouraging to others. I’m pretty sure JB was fascinated by this aspect of the subject in the first place, and will change his mind again in some future (I hope so).
In my opinion, there might be another difficulty in quantum gravity, which is related to but distinct from the good questions to ask, this is the good time to start. It is quite possible that some pieces of the puzzle are still lacking, and it is just too early to start thinking about quantum gravity. In my opinion, one of these pieces might lurk in the quantum mechanics corner.
Anyway, there is no reason to feel depressed about this, since the work done so far in QG already led to considerable progress. After all, mathematics benefited immensely from the work of many people who started to think too early about Fermat’s last theorem…

13. milkshake says:

One thing that this site could possibly achieve (and did, partially) is to puncture the orthodoxy bubble that “ST is a very powerful and beautiful framework and the only game in town”.

The other one is to point at the general problem of salesmanship in presenting the research results – I have seen this in biology and chemistry (including some outright faked work) and I think it is a rather more insidious problem than particular fads and orthodoxy. In chemistry it can still take few years to uncover baloney or lay the hype to rest – and the experiments there are much easier, cheaper so the interesting results could be re-checked by a number of groups.
It is quite easy to fool yourself and from then on it is even easier to start fooling others.

14. Arun says:

Recently I was down in Princeton, and found out that the University Store, traditionally one of the best places in the world to buy math and physics books, has now gone out of the book-selling business, turning it over the Labyrinth Books.

That spoiled my day. Motl-Wotl is piffle.

15. TomD says:

I hate to hear of the “demise” of the U-Store. I spent a lot of my disposable income there as a grad student at Princeton, and have returned there several times since and had a great time browsing and buying.

It’s getting tough to find good technical bookstores. Even with the existence of Amazon, we still need a place to actually see books before buying them. Last summer I had the pleasure of going to the Cambridge University Press bookstore in Cambridge, England, as well as Heffer’s Bookstore, and those were wonderful….

16. Andrew says:

Peter, I think your New Year’s resolution should be to ignore Motl. He appears to be a paranoid crank. Don’t give him the oxygen of attention that he craves…

17. dark-matter says:

Lubos Motl and Britney Spears are identical in every way.
Does that help settle the matter? Let’s move on.

18. Paul Jackson says:

Just as it’s always darkest just before dawn, your report that a sophisticate like John Baez is finally giving up on quantum gravity may be a portent that a new way forward is about to emerge.

Nil desperandum, Peter Woit!

The work of the Brazilian theorists Aldrovandi and Pereira (on de Sitter relativity) looks to me suspiciously like the breaking up of a logjam on a big river of sterile theory. And that’s my pennyworth.

Pushkinean Quantum Gravity (1983-1986)

Dear colleagues!
It is clear that the big turmoil exist inside theoretical physicist’s community. And main controversial problems are the status of quantum gravity and superstring theory (sorry for my English). In such situation I think that for some scientists will be interesting and may be useful to know about QG version which was developed twenty years ago by bright but mostly unknown physicist Alexander Vasilyevich Pushkin (1947-2004) who had worked in Russian Federal Nuclear Center VNIIEF located in Sarov. Unfortunately, A.V. Pushkin’s results in fundamental physics have been published not in full measure, while those published are sometimes of fragmentary nature and mostly in Russian. Below I try to explain his ideas very shortly. Partly they were developed in collaboration with Dr. Gorbatenko M.V. I start by quotation from the book [A.V.Pushkin, “Geometrodynamics” which was written in 1997 and was published in 2005 in Russian by RFNC VNIIEF].
“As a result of a research (January 1983 through April 1986) the author managed to solve the problem of construction of the consistent (divergence-free) quantum gravity theory. Moreover, it was possible not only to prove finiteness of the theory, but also to constructively express its properties in a closed form – in the form of a system of nonlinear partial differential equations, whose solution set includes all the four-dimensional manifolds consistent with the causality principle <>. As it turned out, the construction of a consistent quantum gravity is equivalent to that of unified theory of material fields with unbroken local scale invariance. In the physical language this means that the theory satisfies the fundamental experimental fact, viz. the absence of absolute dimensional scales in the nature.
In the algebraic language the mathematical content of the theory reduces to a unique object, viz. commutative nonassociative algebra discovered by Griess, and a group of automorphisms of the algebra, viz. “Monster”, or “Griess-Fisher Friendly Giant”.
The geometric properties of the theory are expressed in terms of four-dimensional manifolds, whose structure is exhausted by that of two-dimensional surfaces globally embedded in them.
The connection between the two descriptions is established by the theory of representations of the Monster group, which is a theory of representations of some infinite affine Lie algebra of <>. In its turn this means that the quantum gravity theory can be expressed in terms of a system of completely integrable nonlinear partial differential equations, i.e. in that closed form which has been spoken about above. In what follows we will refer to this system of equations as geometrodynamics equations, or simply geometrodynamics.
Eventually, the complete integrability property provides a tool for comparison of one physical process with another by means of representation of invariants of one solution to the equations in terms of invariants of other solution(-s).
The author’s research series (December 1986 through 1992) was devoted to solution of the inverse problem: A system of 10 geometrodynamics equations is given; the structure of mater and objects has to be constructed in the form of relations between their invariant characteristics.
That is, first, it was necessary to determine as consequences from the equations the principal laws, relations and set of basic constants that have been discovered in the nature and formalized in the set of phenomenological approximations (such as Newton and Coulomb laws, Dirac equation for electron, …, many-body coherent systems of quantum continuums, …, and, finally, nonlinear motions of ordinary continuums and up to cosmological-scale astronomical phenomena).
In the course of work on the inverse geometrodynamics problem the author was able to construct a set of quantitative relations among invariants of different-scale physical processes. To date it is already complete enough, which allowed quantitative comparisons of most important physical processes with an accuracy close to the modern possibilities of experimental metrology. In particular, this pertains to the relations between atomic and astronomic systems of units of time, distances, masses. (For separate quantities the calculation accuracy proved higher than their experimental measurement accuracy, see “Monstrous moonshine” and Physics in this book.) “
For first acquaintance with Pushkin theoretical universe let us see on the abstract of report which was presented by him on 2-nd Sakharov Conference on physics, Moscow, 1997.

“MONSTROUS MOONSHINE” AND PHYSICS

A.V.Pushkin

The paper presents some results obtained by the author on the quantum gravitation theory. This theory proves related to geometry of Cayley projective plane and the algebraic structure of the theory to the commutative nonassociative Griess algebra. The theory symmetry group is the automorphism group of Griess algebra: “Monster” simple finite group. Knowledge of the theory symmetry allows observed physical quantities to be computed in the “zeroth” approximation. Results of the calculations, including those for ~ 1/137 and , are presented, with the theory-controlled accuracy of the “zeroth” approximation being higher for some of them by 1–1.5 orders of magnitude than the accuracy of modern measurements.
For me it was most amazing theoretical paper.
And what is about SS? Here I place one more citation from Pushkin book. “In the superstring theory a striking progress has been achieved recently: as few as five theories remain which are actually based on two lattice types in 16-dimensional space. Moreover, it has been proved that they are non-perturbative equivalents and as such are the limiting cases of the more general single theory. What last step should be made in the superstring theory in the direction of the construction of a single theory? Of course, this step is the gravity quantization, which will result in disappearance of the last dimensional scale in the theory, viz. the fundamental string scale. Then the theory will possess the local scale invariance properties and may perform quantitative calculations with non-perturbative methods by translating algebraic relation between physical quantities to different scale levels, including to the level of ordinary phenomena appearing in continuum motions in standard conditions.
In geometrodynamics, i.e. upon the gravity quantization, even this last dimensional scale disappears. In the language of the lattice theory in spaces this means that there should be the only possibility to avoid the need of appearance of dimensional scale: the fundamental root amount is equal to infinity (i.e. there is no separated cell) and the Weyl vector is therewith light-like, i.e. , which also requires no a priori scale. It is evident that the last requirement is readily formalizable at the level of the elementary problem of Diophantine equation solutions (see Problem 5.5). Having solved it, you will find those values of dimension of hyperbolic spaces , which determine the lattice arrangement of the geometrodynamics.”
I think it is enough, because it is impossible to envelope unbounded. If you want some additional information try LANL arHiv (mainly gr-qc), where placed few papers written by Gorbatenko and Pushkin, and where are additional papers only of Gorbatenko. You can try also the recent publication: arXiv:0711.20113v1 [gr-qc] by M.V.Gorbatenko and me. If you know Russian, is it possible to find much more papers which were published by RFNC VNIIEF (Voprose atomnoi nauki I techniki). Now extended English translation of the Pushkin’s book is ready and we (me and Gorbatenko, part of pushing group) are seeking for foreign publishers. P.S. If somebody prefers Loop QG approach, I add that knots appear very naturally in Pushkin s theory.
Happy New Old! (Russian) Year (13 January) and Russian (Orthodox) marry Christmas (7 January).