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Of being bold June 28, 2008

Posted by dorigo in physics, science.
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Scientists should be bold. They are expected to think out of the box, and to pursue their ideas until these either trickle down into a new stream, or dry out in the sand. Of course, not everybody can be a genuine “seer”: the progress of science requires few seers and many good soldiers who do the lower-level, dirty work. Even soldiers, however, are expected to put their own creativity in the process now and then -and that is why doing science is appealing even to us mortals.

You do not need to be a Einstein, or a Fermi, or a Witten, to do good science: but you need to be bold sometimes. You study, understand, ponder on something, and you come up with your own perception of the matter: you create a model of it in your brain, and this enables you to look in the shady corners, and make a bold claim about what one should find there. The claim may have the function of a working hypothesis, or remain a wild bet, a guess you do not pursue further. Usually a working hypothesis allows you to continue your investigation in one direction, giving you some guidance into new territory. A wild bet is more risky, since it exposes you more: if somebody else proves you wrong it hurts much more than if you prove yourself you were on a dead track.

I have made my own very wild and risky bet a couple of years ago, when I predicted that the LHC will not find any signal for new physics beyond the Standard Model. Definitely a bold statement, motivated by my frustration with observing the lack of any real indication that our current understanding of the subnuclear world may be finally crumbling down. Indeed, it was a real bet, which will pay real money. I perceive it as an insurance: I definitely would rather lose it than win it!

Other scientists have made their own, virtual or real bets: claims about what we will eventually discover on the organization of reality. I salute with enthusiasm the latest one, which I read today. Here is what Peter Woit says:

To go out on a limb and make an absurdly bold guess about where this is all going, I’ll predict that sooner or later some variant (”twisted”?) version of N=8 supergravity will be found, which will provide a finite theory of quantum gravity, unified together with the standard model gauge theory.

How’s that for boldness ? This is not about not finding something. It is about predicting how things stand: definitely a high-level claim. And Peter then continues in kinds:

String theory will turn out to play a useful role in providing a dual picture of the theory, useful at strong coupling, but for most of what we still don’t understand about the SM, it is getting the weak coupling story right that matters, and for this quantum fields are the right objects. The dominance of the subject for more than 20 years by complicated and unsuccessful schemes to somehow extract the SM out of the extra 6 or 7 dimensions of critical string/M-theory will come to be seen as a hard-to-understand embarassment, and the multiverse will revert to the philosophers.

This is called going “all in” in Texas hold’em poker: being consistent to the end. The criticism of string theory contained in his successful, highly readable book Not Even Wrong finds here its final justification: string theory is not by itself bad, but investigating it with momentum in the last two decades has not resulted in finding a new stream, but rather in a folding into itself of the discipline along with its extra dimensions, in one of the 10^500 possible ways which all together threatened the perception that most of us have of what doing science should be. Congratulations for your Friday evening boldness, Peter!

Comments

1. Kea - June 28, 2008

Have you been drinking, Tommaso?

2. dorigo - June 28, 2008

Actually, yes🙂 And I smoked the narghile’ last night. Then, I flew to Vienna with a flight at 4AM in the morning… good guess!
T.

3. Evil String Theorist - June 28, 2008

Sounds to me like PW is finally starting to admit that string theory is the correct theory of quantum gravity. I appreciate the sarcasm directed towards this sad fellow in your post.

4. nige cook - June 28, 2008

It’s an interesting post. I think that the main role of people like him is to help separate fact from fiction. It’s too tempting for the mainstream to pass off speculations as facts because everyone within the mainstream group believes that the speculations are the only game in town, and have ‘evidence’ from their self-consistency or their consistency with other speculations.

It will be interesting to see how Peter Woit’s status in particle physics will change, if it changes at all, as a result of his own speculations about the direction particle physics is headed. In his main arXiv paper, http://arxiv.org/abs/hep-th/0206135 he goes into representations of symmetries based on Lie spinor groups and Clifford algebras before coming up with some ideas (page 51) about the electroweak chiral symmetry in low dimensions, points out that there is no real need for or evidence for supersymmetry on page 52, and on page 53 he concludes:

‘The striking lack of any underlying symmetry principle for string/M-theory is matched by the theory’s complete inability to make any predictions about nature. This is probably not a coincidence.’

He is making the point there, and in his book Not Even Wrong (the last chapter) that there is definitely a need for a symmetry group which somehow includes gravity, either to replace or include the Standard Model (the failure of string and loop quantum gravity to make useful falsifiable predictions stems from an inability to really predict particle physics, i.e. to falsifiably predict the symmetry group of the universe).

It’s interesting that he is now changing his position with regards to supersymmetry (albeit without extra dimensions) because the loop divergence problems are apparently not real.

My understanding is that the supersymmetry with N = 8 supersymmetry charges in four spacetime dimensions is supergravity because it has 32 supersymmetry generators and as such includes a massless spin-2 field (accommodating mainstream beliefs about the graviton). Because the number of superpartners for the graviton, i.e. spin-3/2 gravitinos, is equal to the number of supersymmetries, that means that there are 32 gravitinos. The theory looks complicated.

“To go out on a limb and make an absurdly bold guess about where this is all going, I’ll predict that sooner or later some variant (”twisted”?) version of N=8 supergravity will be found, which will provide a finite theory of quantum gravity, unified together with the standard model gauge theory.”

I don’t understand how an version of supergravity, which is just a supersymmetry (adding superpartners with different spin and mass to cancel out divergences in the perturbative expansion of field theories) can be unified with the standard model, which doesn’t include gravity. One reason for string theory was that it was to replace the standard model with a new particle physics that is versatile enough to automatically include gravity. Supergravity as I understand it is just a supersymmetry that supplies gravitons to gravitons to cancel out divergencies in quantum gravity. This isn’t a theory of particle physics or quantum gravity, just a correction to bolt on to such a theory. So his “absurdly bold guess” doesn’t really address the kind of issues he made in his major paper and his book.

I don’t see why there is such enthusiasm for finding a theory for spin-2 gravitons, which could be a red-herring. Nobody the slightest evidence for them. They were suggested by Pauli and Fierz, who pointed out in the 1930s that to get an always-attractive force between two regions of mass energy which are exchanging gravitons, the gravitons need to have spin-2 with (2*2)+1 = 5 polarizations, because the resulting 5-component tensor Lagrangian for the field gives an always-attractive force. (See chapter I.5 of Zee’s http://press.princeton.edu/chapters/s7573.pdf pages 30-34.)

This is only sound if you assume that there are only two masses in the universe that exchange gravitons. Actually, we’re surrounded by immense masses, and should be exchanging gravitons with them. To make quantum gravity make checkable predictions you don’t need to look far. The whole failure of general relativity in cosmology stems from its mathematical flexibility: the Friedmann-Robertson-Walker metric predicts all types of universe depending on the cosmological constant. If you forget classical gravity (GR) and start by looking at the basic facts from a quantum gravity perspective, the Hubble expansion velocity v=Hr derivative is a = dv/dt = H(dr/dt) + r(dH/dt) = Hv + r*0 = Hv = H(Hr). So by forgetting GR and just looking at the physical facts, you immediately predict the acceleration of the universe and therefore the related cc. Next, Newton’s 2nd empirical law of motion tells you that the radial recession of accelerating matter gives an outward force F, which must have an equal inward reaction force, and this might be mediated by gravitons. You can test the idea by calculating the force.

Because nearby matter isn’t receding, it gives zero inward reaction force (mediated by gravitons) towards you. So it “shields” you from gravitons you are exchanging with other, more distant masses in the universe. hence, you get pushed towards the local mass, such as the earth, the sun, and nearby galaxies like Andromeda. Only on larger scales where there’s appreciable redshift, is gravity cancelled out by cosmological expansion. So gravitons with spin-1 are conceivable. This predicts gravity strength correctly within observational errors based on the known Hubble constant and mass of the universe. The idea is usually dismissed out of hand because LeSage and Fatio came up with the idea in Newton’s time, and their version used massive exchange radiations which would cause drag and heat up bodies. However, exchange radiations in all gauge theories such as the Standard Model operate without causing drag or heating up particles, and all Standard Model forces have far bigger coupling constants than quantum gravity! These objections to a physical mechanism don’t apply to gauge bosons. In addition this model seems to be consistent with a simple symmetry that builds gravity into the Standard Model and reduces the number of unknown parameters.

5. nige cook - June 28, 2008

Sorry, there is a typing error above: : … Supergravity as I understand it is just a supersymmetry that supplies gravitinos to gravitons to cancel out divergencies in quantum gravity. …”

Sorry also that my comment is long. Please delete it, if it is unsuitable.

6. Peter Woit - June 28, 2008

“Evil String Theorist”

You seem to have trouble reading what I wrote. The prediction is that real world quantum gravity will turn out to be not a string theory, but a conventional 4d quantum field theory, more explicitly, a twisted or other variant of 4-dimensional N=8 supergravity.

The comment about string theories providing useful variables for studying strongly coupled gauge theories is about their possible usefulness in the QCD sector (or possible other strongly coupled gauge sectors). Gravity is weakly coupled, so for this a string dual (and I have no idea whether such a thing might exist or not), would be useless.

The evidence is mounting that the main remaining argument of string theorists (“QFT can’t quantize gravity, only string theory can”) is simply wrong. I’ll let others decide whether the “sad fellow” description better characterizes me or string theorists who react to the problems of their research program by making anonymous personal attacks on anyone who points these out.

7. nige cook - June 28, 2008

“The prediction is that real world quantum gravity will turn out to be not a string theory, but a conventional 4d quantum field theory, more explicitly, a twisted or other variant of 4-dimensional N=8 supergravity.” – Peter Woit (in reply to Evil String Theorist)

Isn’t supergravity only indirectly a quantum field theory, and then only in 11d (through being related via M-theory – where 11d is a brane on a 10d bulk of the universe – to the landscape of quantum field theories in 10d superstring theory)? Is N=8 supergravity itself a theory of gravitons and other particles, as well as being a theory of their superpartners like gravitinos? I thought supersymmetry in all its forms was just a theory of unobservables superpartners?

8. Sulfur Surfer - June 28, 2008

\”You do not need to be a Einstein, or a Fermi, or a Witten, to do good science: but you need to be bold sometimes. You study, understand, ponder on something, and you come up with your own perception of the matter: you create a model of it in your brain, and this enables you to look in the shady corners, and make a bold claim about what one should find there.\”

It is surprising that you take PW as your example of `boldness\’. The ones who are bold are the ones who are investing their time and effort and imagination to do the calculations, to try to understand what they mean, and test their ideas with new calculations, and publish their results. PW does none of these things, he stands back as a self-appointed evaluator of the efforts of others. This is something orders of magnitude different from the actual work of science, the trying to move back the boundaries of the unknown. You, as a (hard-)working scientist, should appreciate the difference.

9. dorigo - June 28, 2008

Sulfur,

Peter Woit wrote a successful book. He is well known in the field. He has put a face behind his ideas. His blog is read by tens of thousands of people. In the post I linked, and in the text I quoted, there definitely is a good measure of boldness. I disagree that bold scientists are only those who take care of the nitty-gritty details. Take Peter’s statement, put it in the mouth of a unknown theorists on a 10-visits-a-day blog, and you cannot classify that as bold anymore!

There might be a language barrier somewhere; so I check my Webster’s, which says
“bold:
1) showing a readiness to take risk or face danger; daring, fearless.
2) too free in behavior or manner; taking liberties; impudent; shameless.
Plus other definitions. I think it well applies to Peter, much less so to string theorists pursuing obscure lines of research and publishing arcane papers to get tenure somewhere. So, you see, I see no correlation with the number of papers one publishes!

Cheers,
T.

10. Peter Woit - June 28, 2008

“Sulfur Surfer”,

I think Tommaso’s description of me is characteristically overly enthusiastic, but on any “boldness” scale, submitting anonymous blog comments criticizing people is at an end of it far from what bloggers do when they chose to write about something and put their name to it.

Normally I get a lot of complaints about how negative I am about everything in theoretical physics, but in this case I was just straightforwardly trying to draw some attention to research which I think is very interesting and quite admirable. For some reason, this is really upsetting string theory partisans.

I don’t know about boldness, but I’m well aware how much harder it is to come up with some new understanding of nature than to come up with a new blog posting or write a popular book. I spend a lot of my time struggling to do the first, but also some time doing easier things, and I’m glad that some people seem to get something out of those. The complaints seem to come almost entirely from those who disagree with the point of view I’m expressing, but don’t have a serious argument against it, so have to go for the ad hominem one.

11. Sulfur Surfer - June 28, 2008

\”string theorists pursuing obscure lines of research and publishing arcane papers to get tenure somewhere.\”

1. The research that PW was so boldly speculating about is largely being carried out by string theorists, so it is inconsistent to turn around and accuse them of `obscure lines of research.\’

2. It is easy and cheap to predict some `variant\’ or `twisted\’ version of N=8 supergravity. If such a variant exists, it will be the hard work of many hours and many physicists (probably many of them string theorists) to find it. They are the bold ones.

3. Do you view your own career as `publishing arcane papers to get tenure somewhere\’? If not, why are you so ready to assume that some other group of scientists is less noble than you?

12. anonymous - June 28, 2008

Sulfur Surfer,

The boldness with which string theorists “test their ideas with new calculations” (your words) isn’t scientific: the scientific way to test ideas is with experiments, rather than by just adding “new calculations” that again can’t be checked observationally.

There’s nothing scientifically “bold” about manufacturing a vast number of papers in an experiment-free mainstream endeavor which for decades has remained out-of-touch with physical reality.

13. Tony Smith - June 29, 2008

Peter Woit’s prediction
“… that real world quantum gravity will turn out to be not a string theory, but a conventional 4d quantum field theory, more explicitly, a twisted or other variant of 4-dimensional N=8 supergravity. …”

is indeed bold, so it is worth at least a couple of comments:

1 – Supergravity is based on naive 1-1 fermion-boson supersymmetry, for which there is (despite decades of careful search) absolutely no experimental evidence.
Therefore,
it seems to me that Peter Woit’s bold prediction will remain useless unless and until some experimental evidence for naive 1-1 fermion-boson supersymmetry is found,
and
that future LHC results may fairly be thought of as crucial for the survival of the bold prediction.

2 – For N=8 supergravity to be useful, it must include the Standard Model gauge group that is (roughly modulo some technicalities) SU(3)xSU(2)xU(1).
The obvious Standard Model gauge group for supergravity is SO(8),
but as Freund says in his book Supersymmetry (Cambridge 1986):
“… Were we to take phenomenologically seriously the gauged SO(8), we would have to concentrate on its amximal SU(3)xU(1)xU(1) subgroup and attempt to identify the SU(3) factor with the color gauge group, one of the U(1) factors with … electromagnetism, and the other U(1) either with the “third” component of Glashow’s weak SU(2) or with some yet unknown abelian gauge group.
In either case the charged weak gauge bosons … would not fit into SO(8).
They would have to be composite, qualitatively different from the gluon, the photon, and possibly even the Z0.
This is disappointing. …”.
In order to avoid the restrictions of SO(8) as supergravity gauge group, it is possible to introduce a local SU(8) gauge group,
in a way described by Freund:
“… a local SU(8) symmetry would require 63 massless vector particles … the gauging of SU(8) is done nonlinearly through “composite” combinations of scalar fields …”.
So,
either the supergravity SO(8) is too small to be realistic,
or
you have to introduce 63 massless vector particles of SU(8),
which is a lot of unobserved particles that (like the many unobserved 1-1 fermion-boson superpartners) must be accounted for by experiment.
Again, there is as of now no evidence whatsoever,
but Peter Woit can say that he is waiting for LHC results.

In light of those two comments,
my question to Peter Woit is:

If the LHC does not find evidence for the stuff required by your bold prediction of supergravity within a few years,
will you consider your prediction to have failed,
or
will you (as has been a common practice by many theorists in the past few decades) move the goal posts and say that your prediction is OK until some future experiments (perhaps CLIC or beyond) are done ?

Tony Smith

PS – In case that anyone might be interested,
I have put on the web at
http://tony5m17h.net/E8physicsbook.pdf
a physics model with detailed calculations that can today be compared with experimental observations.
It is 367 pages, a pdf file about 9 MB in size.
It covers a lot of things,
so if some things in it are not to your taste,
you might look through the table of contents and perhaps find a section or two in which you might find some stuff that you might consider interesting.

14. Tony Smith - June 29, 2008

For some reason a lot of smileys showed up in my immediately preceding comment,
wherever I tried to write:

eight
followed by
a parenthesis

I don’t know how to correct the comment
but

please where you see a smiley try to read it as

SO( eight parenthesis closed
or
SU( eight parenthesis closed

Tony Smith

PS – It seems that the invading smiley faces
did not show up if the closed parenthesis
were immediately followed by a period or comma.

15. Myke - June 29, 2008

Thanks Tony for your efforts on the E8 book, really appreciated! I’ve spent the last few decades, on and off, looking at string theory from many angles, even with seemingly silly substitutions, but it still seems flawed! A big problem is that it insists on a massless graviton, when in reality the graviton should coincide with the Planck mass, which means that detecting gravity waves more than ‘several’ AU from their source ain’t going to happen – another null result that will cause many to look up and ask the right questions! However, with regards to supersymmetry, and all that depends on it, the problem seems to be one of necessary resolution (about 100 eV) rather than sufficiently energetic collisions producing SUSY particles. My bold prediction is that the LHC will be remarkable for its lack of discovery, but its hints of things to come will drive a revival of an even better SSC, one that can see the true Higgs domain around 34 Tev…

Myke.

16. Plato - June 29, 2008

Topoi,Topoi,

C.Isham is bold.

17. Kea - June 29, 2008

Hurrah, Plato! I think you are very clever.

18. Kea - June 29, 2008

And it’s toposes, not topoi.

19. Sulfur Surfer - June 29, 2008

By the way, Tommaso, my original comment made no mention of string theorists, you are the one who brought them in via a cheap shot. The bold ones in this N=8 story are Zvi Bern, Lance Dixon, and their collaborators, who have devoted many years of their lives to figuring these things out.

One of the most important things in science it to give credit appropriately. Bern, Dixon, et al are truly bold in the sense that you describe at the beginning of your post. You instead give credit to someone who was nowhere around when the work was.

20. Peter Woit - June 29, 2008

Tony,

I’m not claiming that N=8 supergravity is a valid TOE. That idea has well known problems. I am predicting that some 4d QFT with some sort of exotic version of supersymmetry will be a TOE, evading the problems with renormalizability of gravity by whatever unknown mechanism is at work in the N=8 supergravity case.

Standard forms of supersymmetry have the well-known problem of predicting superpartners, thus requiring complex and ugly mechanisms for supersymmetry breaking. The “twisted” form of N=2 supersymmetry used by Witten in his work on TQGT is an example of the sort of conjectural variant of supersymmetry I have in mind which evades this problem.

I certainly don’t know how to write down a viable theory of the kind I think might exist. If I did I’d be writing a paper about it. Instead, this is rank speculation, fit for blog postings and comments. I hope it inspires someone smarter and harder-working than me to come up with something serious.

21. dorigo - June 29, 2008

NIgel, #8: I refrain from answering your comment because I am unable to do it appropriately. I can only say that I believe PW is not actually changing his views on SUSY, if I read him correctly.

#10 Peter, I grew to be a fan because, of the things I understand in your book and in your blog, I agree with most. So it is not shameful to be overenthusiastic🙂

Sulfur #12, I am not claiming anybody is nobler than me because of the research I do and the one they do. All I am saying is that I do not perceive what they do as physics, while it all looks to me as a way to go with the flow and just manage their career. Of course, I may well be wrong. To paraphrase Groucho: this is my opinion, and if you do not like it, well – I have others.

Hi Tony,
thank you for linking your book here. While I confess I did not read it fully, I think your ideas deserve some exposure. As for PW’s predictions, if they fail it’s not a terrible thing: we are all gamblers here.

Sulfur, I give credit in an extremely incomplete, disuniform, and arguable way -what’s the point ? This is not about giving credit. I liked what PW wrote and I published it here. I do not like the way string theory has monopolized the field, and I say it. Whether I like some thing or not, I am not making too much harm -it’s my opinions, after all. Sorry if it bothers you.

Cheers all,
T.

22. Peter Woit - June 29, 2008

“Sulfer Surfer”,

“One of the most important things in science is to give credit appropriately. Bern, Dixon, et al are truly bold in the sense that you describe at the beginning of your post. You instead give credit to someone who was nowhere around when the work was.”

Tommaso is not crediting me with the work or achievements of Bern, Dixon, et. al. That would be idiotic, and he’s not an idiot. He is crediting me with making a completely speculative and not well-defined conjecture about where to look for a TOE, a place at least with the virtue of being quite different than where much of the particle theory community has been looking for the last nearly 25 years (and thus perhaps meriting the adjective “bold”}. I will accept credit for this, while acknowledging that speculative conjecture is cheap, so this one probably isn’t worth much (nor is it particularly original; as I pointed out, Hawking and others were promoting this decades ago).

23. Eric - June 29, 2008

This is ludicrous. Everyone knows that supergravity and string theory are intimately related. It seems to me that what PW is doing is starting to hedge his bets a little, so that if something like supersymmetry is found at the LHC he can at least claim that he was a supporter of supergravity. He can then always dismiss his statements expecting supersymmetry to not be found as the result of being cautious. At any rate, my prediction is that once the results from LHC are in, blogs such as his and the associated crack-pots with a chip on their shoulder towards to the establishment (string theory) will begin to disappear.

24. dorigo - June 29, 2008

Hi Eric,

I have recorded your prediction. It is not too bold but genuine, and I think it deserves attention. Since, however, it is made by two parts, let me simplify it. You are
1) expecting LHC to tip the scale toward string theory,
and you are
2) expecting blogs criticizing string theory to disappear afterwards.

This is good news. To make matters more interesting, are you willing to put money on that ?

Cheers,
T.

25. Sulfur Surfer - June 30, 2008

Tommaso —

I do not want to beat this subject into the ground, but you are the one who introduced gratuitous criticism of string theory into the discussion, and I think that you still do not get it.

Yes, you have your opinion of string theory. But it seems to be based on ignorance, as evidenced by its own inconsistency: the work you yourself praise is closely related to string theory, and is being carried out in part by string theorists (have a look at the attendees at the conference Peter refers to). Moreover, this is just one of O(10) current threads of research in the field, each of which has as much long term promise as this one.

You may wish to express such ill-informed opinions on your blog, but you go much further when you challenge the character (i.e. `careerists\’) of an entire group of scientists. Do you really wish your blog to be identified with such prejudices? You must be aware that you are a member of a group that suffers from similar generalizations – do you think that it is sufficient to blow those off with a Groucho Marx quote also?

Finally, let me say, as I should have said more clearly, that the first part of your post is an excellent description of boldness in scientific research, and the post would have been perfect if you had actually singled out exemplars of this, such as Bern-Dixon-Kosower.

26. dorigo - June 30, 2008

Sulfur: I of course am no expert on the matter, and my opinion may be indeed based on ignorance as you say. Less so my perception that particle theory has been dominated during the last two decades by one field of research I do not have much sympathy for, and which has shown little for the investment.

If your point is my ignorance, than I may accept it. if it is the fact that besides being ignorant I have prejudices, and these fill up my blog posts, well… I can also accept this, but is it really that big of a deal ? A blog doing scientific divulgation which has no personality would be less interesting in my opinion.

Cheers,
T.

27. Amitabha - June 30, 2008

Not too many bold predictions in your comment section …
I’d like to see a prediction of the Higgs mass. (My hunch — not a prediction — is that no definite signature of the Higgs will be found, nor of SUSY.)

28. Tripitaka - June 30, 2008

Yes more bold predictions please all! Especially ones backed up with $ bets. Why not, it makes it all a bit more interesting for the ones ultimately footing the research bill, ie Joe/Jill Taxpayer.

29. Myke - June 30, 2008

See 15 above… Any fair wagers?

30. nige cook - June 30, 2008

‘I am predicting that some 4d QFT with some sort of exotic version of supersymmetry will be a TOE, evading the problems with renormalizability of gravity by whatever unknown mechanism is at work in the N=8 supergravity case.’ – Peter Woit, comment 20.

That’s clear. As for the evidence for supersymmetry, Edward Witten believes that supersymmetric partners may be dark matter, see http://www.youtube.com/watch?v=iLZKqGbNfck (at 7 minutes):

‘The dark matter could very well be a cloud of these almost invisible supersymmetric partners. The idea is that this dark matter cloud envelops the whole galaxy including our solar system, so they are passing through the earth all the time, for the most part not interacting because they couple so weakly with ordinary matter.’

Surely if dark matter consists of supersymmetric partners, the mass of the latter could be predicted by the known observational limits on the amount of dark matter in the universe? E.g., since there is on the order of 10 times as much dark matter as visible matter, then the masses of supersymmetric partners might be expected to be 10 times the masses of the observed particles, and in that case they would have been observed long ago.

31. dorigo - June 30, 2008

Nige, that’s wrong. Fewer particles with higher mass can exist and give the fraction of DM seen. Similarly, the DM candidates could well be very light, and very many! And even if they are light, they might not have been seen for various other reasons. Hell, we do not even know the mass of neutrinos…

Things are more complicated, structure formation depends on the velocity distribution of the DM candidates too. For sure, you cannot construct syllogisms of that kind pretending they hold water.

Cheers,
T.

32. Eric - June 30, 2008

Dear Tommaso,
Yes, I would be willing to put money on these predictions:

1) TeV scale supersymmetry will be discovered at LHC by 2011.

2) The lightest Higgs will be discovered with a mass around 117 GeV.

3) Blogs such as this one and Woit’s will start to die off once the results from LHC are known.

33. Peter Woit - June 30, 2008

Just a comment on whether I’m “hedging my bets”.

My opinion about supersymmetry has always been the same: there’s something very interesting going on, but the standard version of it doesn’t work. Supersymmetry is behind some fantastic mathematics (TQFTs), but generally in a “twisted” form. The standard form of it has not been so mathematically interesting, and has the deadly phenomenological problem of pairing observed particles with unobserved ones. Maybe the LHC will give some insight into this, my prediction is just that we’re not going to see the MSSM or any extension of it.

We’ll see how LHC results change the behavior of Eric’s “crackpots”, but more interesting will be the question of how they change the behavior of the particle physics “establishment” which he identifies with string theory. If there is no sign of the MSSM or string theory at the LHC, will those who have been pushing this for the last quarter-century cease being the “establishment” and become “crackpots”?

34. dorigo - June 30, 2008

Dear Eric,

of the three, the last one is definitely the boldest, but it is also bordering the foolish, unless you prevent me or Peter from taking it!

I would be willing to take the second one, provided you lose it if no Higgs is found by LHC by 2011 OR if LHC finds no >=5-sigma signal of a new particle with mass compatible with 117 GeV at >=5% CL by 2011. But I have my bet out already… Maybe somebody else could take it ? In any case, you have to make your name, affiliation, etc. be known if you want to be taken seriously.

Cheers,
T.

35. dorigo - June 30, 2008

Hi Peter,

in my experience, the most vocal and stubborn partisans are those who recycle themselves most easily as soon as they understand they have failed. I think we are going to see a lot of horse-jumping in the next few years, and they will continue to represent the establishment.

Cheers,
T.

36. Eric Mayes - June 30, 2008

Dear Tommaso,
Let’s make the third prediction a condition of winning or losing the first two. If supersymmetry is found as well as the Higgs with a mass 117 +/- 2 GeV, then you agree to give up your blog. Since you and Woit seem so sure that supersymmetry and string theory are all some kind of scam, why don’t you show some boldness if you are proved wrong?

37. dorigo - June 30, 2008

Hah! My blog ? Fine, but we need to agree on its value, because I expect you to pay cash if I win, since you do not have a similar commodity to offer in return.

A simple way to appraise a blog is to count its potential hits for the next 20 years, and assign a value to each hit. I think you would agree that a hit is worth at least a penny. In 20 years, a very conservative estimate is of 8 million hits. So that makes this blog currently worth about 80,000 US$.

Another way is to use the utility you can find here.. For my blog, it returns the value of 62,663.94 US$.

Since the two above estimates are roughly in agreement, and since the bet will only be payable in 2012, and by then dollars will have lost value, while the blog will have increased it, I think it is fair to agree on a round figure: 100,000 US $.

If you agree, we can start looking for a way to make this a binding agreement.

Cheers,
T.

38. Thomas Larsson - June 30, 2008

Eric, it is a bad idea to pin down a date like 2011. Remember that Lubos lost his experimental-susy-by-2006 bet that way; if I understand correctly, his renegotiated deadline is today. Whereas I do not doubt that LHC will eventually produce interesting physics, there maystill be unexpected delays ahead.

Besides, Larsson’s theorem guarantees that susy will not be discovered at the LHC.

39. nige cook - June 30, 2008

‘Nige, that’s wrong. Fewer particles with higher mass can exist and give the fraction of DM seen. Similarly, the DM candidates could well be very light, and very many! … For sure, you cannot construct syllogisms of that kind pretending they hold water.’ – Tommaso Dorigo

Thanks for responding to this problem, but supersymmetry uses an exact correspondence between the existing observable particles and their supersymmetric partners, such as the 1:1 correspondence mentioned by Tony Smith in comment 13, with one supersymmetric partner per observed particle. This 1:1 ratio, with each observed partner having exactly one supersymmetric partner, implies that the mass ratio of (supersymmetric partners)/(observed particles) = (density of supersymmetric matter)/(density of observed matter).

So if supersymmetric partners were dark matter, since there would be the same number of such partners as known particles, and therefore the same number-density (particles per cubic metre) in the universe, so the ratio of dark matter to visible matter would be directly equal to the ratio of the (mass per supersymmetric particle)/(mass per observed particle).

So with respect, I’d suggest that the theory which doesn’t hold water is supersymmetry. Also, the supersymmetric partners must be found in the same place as the high energy physics is normally occurring (i.e. a small volume near the core of a fundamental particle, where field strengths are immense), so that they can cancel out divergences and allow fundamental forces to unify very close to particle cores. If supersymmetric partners were far away from this region, they wouldn’t be able to partake the necessary interactions for force unifications at small distances (high energy).

So I don’t see how dark matter (if it is superpartners) can be dissociated from ordinary matter. If there is only one supersymmetric partner per observed particle and those particles are required to make forces unify at high energy, they must all be closely confined to the region of space within a very small distance of the core of fundamental particle, otherwise they wouldn’t be present where needed to allow fundamental forces to unify at high energy/small distances.

40. goffredo - June 30, 2008

What will future scientists think of all this heated discussion.

We scientists have a notion of the history of science that is greatly distorted. Actually we are ignorant of history. Before Special Relativity there was a very heat debate about the nature of the ether. Then Einstein came along and today we don’t spend even 1 minute in telling these things to our science students. Hence our students cannot get the gist of the debate of the time and, unless they read about the history, they will, if they find themselves teaching, keep propagating the ignorance across to the next generation of science students. Similary we have all heard about how medieval thinkers debated about the sex of angels or how many could be crammed on a needle point. None of us, unless knowledgable of medieval thinking, can have a clue of the debate and appreciate how intelligent those thinkers were. Instead we have a feeling of superiority. We kind of look down on how they thought.

How ill future science students look at us?

41. dorigo - June 30, 2008

Nige, there is one feature you are not considering. Actually, two. One is a misunderstanding: the exact correspondence does not need that if the universe contains N electrons it also contains N selectrons. It only means that there is the same number of kinds of particles and sparticles!

The second is that there is something called R-parity, which prevents the proton from decaying into pions -which in the SM can’t happen, while in SUSY could. R-parity forces SUSY particle decays to always produce a sparticle at the end. The lightest of these is neutral, and it is the DM candidate. Only the lightest one! Because R-parity is conserved, these particles are stable -can’t decay to anything- and they constitute DM. So, only the mass of this one body is constrained to be such that, multiplied by the abundance, gives the 20% of DM in the universe we need.

Cheers,
T.

42. dorigo - June 30, 2008

Jeff, that’s a good point of course. But what can we do… Sure, teach well our students. Not at all easy, as you know, being a very good teacher.

It is hard to escape the curse of future generations!

Cheers,
T.

43. db - June 30, 2008

Goffredo asked: “How will future science students look at us?”

If they are theoreticians I think they will be envious, not of us, but of the previous generations, especially from 1900 to 1975. That really was the golden age of theoretical physics. I’m pretty sure they will have analysed last thirty years with bemusement and will have worked out why the theoretical community allowed itself to be seduced into such an unproductive cul-de-sac. And hopefully learned the lessons.

If they are experimentalists they will also be very envious of this generation’s marvelous discoveries in neutrino physics, precision cosmology, astrophysics and condensed matter physics. And I’m sure the construction of the LHC will be seen as an heroic and amazing achievement, especially when contrasted with the vast billions being wasted on armaments. But probably the end of the line for terrestrial particle physics for many decades.

An oasis in the maelstrom, if I may mix my watery metaphors.

44. goffredo - June 30, 2008

Hi Db
I agree with you. As an experimentalist that admired good solid theory and model building from 1900 to 1975 plus some more years I was writing from the experimentalist’s perspective (yours too I gather) and provoking the data-less and experiment-less “theorists”. Many are VERY smart people indeed but the irony is that future generations will, I fear (history does teaching many a thing), lust lable them as a dead-end moment in history with the same superficial superiority that we reserve the many medieval geniuses. The diserved respect and so will the present day geniuses but most people in the future will be too busy to spend any time to reconstruct their efforts.

45. Tony Smith - June 30, 2008

Peter Woit said that his prediction involves
“… some sort of exotic version of supersymmetry … evading the problems with renormalizability of gravity by whatever unknown mechanism is at work in the N=8 supergravity case …” as related to the work of Zvi Bern.

Zvi Bern, in his Paris 2008 slides, said
“… We consider the N = 8 theory of Cremmer and Julia. 256 massless states … Every explicit loop calculation to date finds N = 8 supergravity has identical power counting as N = 4 super-Yang-Mills theory, which is UV finite. …”.

In 1981 (Comm. Math. Phys. 80, 443-451)
Geometrical Structure and Untraviolet Finiteness in the Supersymmetric sigma-Model,
Alvarez-Gaume and Freedman said:
“… N = 4 supersymmetry … requires … hyperkahler …these are the first quantum field theories which have been shown to be ultraviolet finite, although power counting arguments indicate divergence to all orders …
we believe that the ultraviolet finiteness properties found here should be valid for supersymmetric sigma-models on any hyperkahler manifold …
In the case that the division algebra is the quaternions [hyperkahler is based on quaternions], there is a basis with … units which satisfy the Clifford algebra property …
One may hope that these geometrical methods … may be applied in four dimensional field theories, where the N = 4 supersymmetric Yang-Mills theory has been shown by calculations to be ultraviolet finite in 2-loop and 3-loop order. …”.

Since N = 8 supergravity has SO(8) structure with triality,
and its structural relation to octonions is somewhat analagous to the quaternionic hyperkahler structure described by Alvarez-Gaume and Freedman,
it is not surprising to me that Bern et al find interesting UV finitness results.

I feel that Peter Woit’s “unknown mechanism” is due to division algebra / Clifford algebra structure
and
that his “exotic version of supersymmetry” is based on triality relations between half-spinor fermions and vectors, combined with Clifford algebra relation of vectors with bivector gauge bosons,
so I think that Peter Woit is correct that
“… a viable theory of the kind … might exist …”.

In fact, back in the 1980s when I began to work on my physics model, I started with N = 8 supergravity and, when I realized that its detailed structure was not physically realistic,
my primary motivation was to build something based on Clifford algebras that would be realistic yet still have the nice symmetric properties,
and now, after a couple of decades of work,
I think that my present model does that pretty well.

Tony Smith

46. Lubos Motl - June 30, 2008

For crackpot Larsson: I certainly haven’t lost the bet by today.

drg t s smwht msng t tk th smllst chckn lttl n th wrld wh nl ss mdst thngs tht wr blvd t b tr 25 rs g bt hv bn prvn ncrrct b nwr rsrch nd clm tht h s bld spcll f h rsks bsltl nthng nd spcll f h s srrndd b mntl crppls wh hppl t th sht h kps n wrtng nd s hw wll t tsts mst rdnr ppl r smpl dts strtng frm wt nd

Bold things are what people like Newton, Einstein, or string theorists are doing.

[TD’s note to readers: sorry, but Lubos had a bad evening and his coprolalic personality took control. Had to disemvowel the second paragraph. Lubos, don’t take it personally – I am sure you will come back to your senses some time tomorrow and regret your outburst of trivialities.]

47. dorigo - July 1, 2008

Hi Tony,

I refrain from commenting what you wrote because I feel I know too little about it – but thank you for it…

DB, I think the LHC experiments have work to do ahead of themselves if they want to prove their worth! It is by no means clear to me that we turn them on and oopla, here comes a discovery after another. It will be tough, hard work for a decade, and then maybe we will be able to look back in pride… I look forward to it though!

Jeff, you know – you touch a point here. I think the future has less and less spacetime left for history! I see the trend. Encyclopedias are substituted with internet searches, reading with browsing, newspapers with online journals. And the focus of all is the present and the future, not the past. When I see my son reading much less than I did at his age, I am not too worried: I know it is not him, but a general trend. And who am I to decide it is a bad trend ?

Cheers,
T.

48. goffredo - July 1, 2008

Tommaso
actually I am more optimsitic than I sound. I really do think that people are more and more interested in history. Indeed more and more quality books are written about history for a larger and wider reader than in the past. Even the history of science is finally being told in ways that does justice both to history and to science. Indeed science is even more interesting when one looks closely at what stimulated or castrated lines of thought and action. Indeed the best antidote against the brain-washing propaganda and incredible waste of human resources of this or that school of theorists out of touch with data and experimentation is telling history. Philosophy is by far less effective and there are serious risks in trying that approach. Philosophers without a knowledge of history can do more damage than historians ignorant of philophy.

Jeff

p.s. I believe people read BOOKS now more than what they did in the past! How many book you read when you were small compared to your son should be contrasted with how many people did not read books or anyhting at all when you were small. When I was young the books available were orders of magnitude fewer and by far more biased (ideological or fairly tales). Today there is a much wider assortment of topics and historians (more people with different approaches and backgrounds) and I feel that it is far more interesting to read today than it was 40 to 20 years ago.

49. db - July 1, 2008

T.,
I don’t recall predicting a flurry of results once the LHC is turned on. What I believe is that future generations will marvel at the sheer feat of constructing such an awesome machine, whether, as I suspect, it yields only limited new results, or, as I hope, it opens the door to important new phenomena. I’m by no means convinced we’ll even see a Higgs particle let alone any evidence of supersymmetry. But I wouldn’t bet against the Higgs, I just won’t be particularly surprised if it turns out that something like dynamical symmetry breaking is at work instead.

As for young people reading less, there I tend to agree. The enjoyment and pleasure from reading a book is something that fewer and fewer young people experience, mainly because, like my kids, they prefer to get their information instantly online. But I’m confident that as they grow older they will discover the pleasure of books.

50. nige cook - July 2, 2008

‘One is a misunderstanding: the exact correspondence does not need that if the universe contains N electrons it also contains N selectrons. It only means that there is the same number of kinds of particles and sparticles!’ – Tommaso

The number of massless bosons is not conserved, so the fact that the superpartners have a spin which is different by 1/2 h-bar from the corresponding observed partners, means that – as you say – there is not automatically an exact correspondence in the number of particles to their superpartners.

However, the massive spartners must be created somehow in the big bang, taking a lot of mass-energy. Since they interact so weakly in the universe today, they’re presumably conserved simply because they are weakly interacting. The absolute abundance ratio would depend on the process by which spartners were formed and the history of their interactions since formation (from the time the particles and their spartners were formed in the big bang). I don’t see any reason why there the ratio should differ from 1:1. That would be the simplest assumption for creation of spartners: in the big bang there’s a high-energy (so far unobservable in particle accelerators) reaction whereby energy is transformed into a particle and a corresponding spartner. If you get more or less than a 1:1 ratio, the theory really needs to explain why that is so. If there is no explanation for such features, the theory is endlessly adjustable like epicycles to start off with. If the ‘theory’ is vague enough, it can’t be science because there is no specific theory to investigate.

‘The second is that there is something called R-parity, which prevents the proton from decaying into pions -which in the SM can’t happen, while in SUSY could. R-parity forces SUSY particle decays to always produce a sparticle at the end. The lightest of these is neutral, and it is the DM candidate. Only the lightest one! Because R-parity is conserved, these particles are stable -can’t decay to anything- and they constitute DM. So, only the mass of this one body is constrained to be such that, multiplied by the abundance, gives the 20% of DM in the universe we need.’ – Tommaso

Since the other spartners are unobserved to date, they must be stable because they’re weakly interacting (or we’d have seen them).

Thanks for replying!

51. nige cook - July 2, 2008

Stability is relative, not absolutely determined. Something that’s extremely weakly interacting or that takes such a long time to either decay or interact that nobody observes it (e.g. the alleged decay of the proton) is effectively stable. So I don’t see any proof that the proton doesn’t decay into pions. Some have claimed for I think SU(5) that the proton decays at a rate too low to be observed. You could apply the same argument to get rid of R-parity and allow the proton to decay into pions with such a long half life that the chance of observing the decay in the lab is practically zero. But thanks again for the explanation.

52. dorigo - July 2, 2008

Hi Jeff,

good thing to know that there still are optimists around😉
As far as total number of books read I am not sure, but as far as number of books read per person with access to them, I tend to believe we are going down!
In any case I agree with you, history books have improved dramatically.

Cheers,
T.

53. dorigo - July 2, 2008

DB, I was not intending to put words in your mouth… My point was that indeed there is a lot of work ahead. But it is certainly also true that CMS and ATLAS are mindbogglingly complex, heroic endeavours. I have heard the statement that these experiments are the most complex constructions ever made by humans, and I tend to agree. One would have to compare them with the most advanced space missions, nuclear submarines, giant dams, but the sheer complexity of the detectors is probably unrivalled.

Cheers,
T.

54. dorigo - July 2, 2008

Hi Nige,

ok, my explanations were a bit too handwaving, but you get the point. I think equilibrium conditions in the first instants of the BB does call for some simple relations between particle and sparticle number densities, but it is not so simple to conclude that for each baryon there must then be a sbaryon…
In any case, the reason why we may not have seen sparticles is because they are more massive. Equilibrium arguments cannot be applied to particles with orders of magnitude of difference in their masses.

Or this is what SUSY enthusiasts believe…

Cheers,
T.

55. Plato - July 2, 2008

Kea:And it’s toposes, not topoi

Maybe Poincare may of hoped for “the singular” and as well, “today?”

Who knows “what rests” in the valleys.A Topoi, or Toposes?:)We know there is a developmental process already in place, and some have not come to recognize it yet by the work of Mandelstam?:)

Best,

56. island - July 2, 2008

It may be naive of me, but db’s last two posts ring perfectly true to my understanding. The only thing that the LHC will find will be proof that science lost it’s way long ago.

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