Some wag at the Wall Street Journal put the headline Don’t Buy Into the Supercollider Hype on today’s Op-Ed piece by Michio Kaku about the LHC, which describes its significance as follows:
The LHC might shed light on the “theory of everything,” a single theory which can explain all fundamental forces of the universe, a theory which eluded Albert Einstein for the last 30 years of his life. This is the Holy Grail of physics. Einstein hoped it would allow us to “read the Mind of God.”
Today, the leading (and only) candidate for this fabled theory of everything is called “string theory,” which is what I do for for a living. Our visible universe, according to this theory, represents only the lowest vibration of tiny vibrating strings. The LHC might find something called “sparticles,” or super particles, which represent higher vibrations of the string. If so, the LHC might even verify the existence of higher dimensions of space-time, which would truly be an earth-shaking discovery.
If I were an experimentalist or accelerator scientist working on the LHC, I might have a problem with the fact that the biggest media outlets are having theorists, often string theorists, be the ones to tell the public about the LHC (yesterday was Brian Greene’s turn, in the New York Times). Many such stories imply that the LHC will somehow tell us something about string theory, while even one of the blogosphere’s most enthusiastic string theory supporters puts the probability of this at about half of one-percent.
For some hype-free LHC predictions based on serious science that I fully endorse, see Resonaances, where the probability of seeing anything relevant to string theory isn’t even listed, and supersymmetry is given a one-tenth of one percent chance, on the grounds:
1% is a typical fine-tuning of susy models, and the additional factor of .1 is because it makes me puke.
which seems about right. The probability of the LHC producing black holes is given as something exponentially small, somewhat less than the probability of producing dragons.
I think the reason for the op-eds is that theorists are the ones who write books and, consequently, have a higher media profile. If you’re an editor, wouldn’t you rather have an op-ed by someone the public has heard of rather than someone closer to the experiment but a total unknown?
Actually, anyone who’s really objective would asses the probability of observing supersymmetry at LHC as more like 70%. And regarding the Higgs mass, the most likely value is mH = 117 +/- 2 GeV, a result which one gets from the MSSM with radiative electroweak symmetry breaking, when combined with other experimental constraints.
You’re right, maybe they should have invited LQG theorists to write the op-ed’s, about the search for particles they don’t even have in their theories 😉 If evidence for extra-dimensions is found, than I see it as a full victory of string theory, not of Kaluza and Klein, or of a particular phenomenological model. The reason is that any phenomenological model with extra-dimensions imposes the additional dimensions as a working hypothesis, while in string theory it’s a consequence, an absolute necessity! Same with supersymmetry. The Higgs might be less clear that it is a direct consequence of string theory, but it’s also much less exciting theoretically as if you find evidence for the other two.
Most definitely not. If I understood correctly, the point is that the experimentalists should be the stars here, since it’s they who are most closely related to the machine. I thought exactly the same thing yesterday when I read Greene’s article. Quite a good article, by the way, but could well have been written by Aymar, or someone else in direct contact with the LHC.
Reading this final sentence of Kaku’s article, I wonder what hype we shouldn’t be buying according to him. The idea seems to be to replace all the Apocalypse crap by Genesis crap.
Wow, Jester just put $10000 in a bet with LM. I do admire people who are willing to put the money where their mouth is, unlike some other critics of SUSY.
bpz,
Betting with Lubos has its problems, including that of counterparty risk. I was tempted for a while by the idea of contacting Kane or Raby to offer a bet, but two things stopped me:
1. While I think any of the known SUSY extensions of the SM is worth betting against (because if they had anything to do with the electroweak breaking scale, we’d have seen evidence already, and the need for SUSY breaking makes the things ugly), there is some beautiful underlying mathematics, and I wouldn’t want to bet against the existence of some still-uninvestigated “twisted” form of SUSY.
2. As ellipsis and others have noted, just about any experimental anomaly can be explained by invoking some SUSY model or other. I think there’s a pretty high probability that at some point there will be a claim of seeing something that doesn’t agree with the SM coming out of the LHC experiments. This may turn out to be something that goes away on closer investigation, or it may survive and be very interesting, but in either case we’ll see all sorts of claims that this is “evidence of SUSY” and it may take a long time to sort these out.
One thing I’d be definitely willing to put some money down about would be string theory unification. But the problem with this is that it predicts nothing at all one way or another about what the LHC will see…
Peter,
You said, “because if they (the superpartners) had anything to do with the electroweak breaking scale, we’d have seen evidence already..”
I have to strongly disagree with this statement. Whether or not we see evidence of it or not depends on the exact masses of the superpartners, which we don’t know. The only thing we do know is that they should be near the TeV scale if supersymmetry solves the hierarchy problem. It should be noted that this scale will only fully be explored by LHC, and so the superpartners should be seen there. In truth, superpartners are probably being created as we speak at the Tevatron, but not at a sufficient rate to generate a definite signal above the standard model background. On the other hand, the recent constraints on the Higgs mass being in the range 114-135 GeV strongly hint towards supersymmetry.
Eric Mayes (=Susy Q = Victor),
Please stop posting the same argument using different pseudonyms, and ignoring my response. You’re wasting my time.
http://www.math.columbia.edu/~woit/wordpress/?p=874#comment-43420
this quote is from the cosmic variance blog cited above:
Evidence for or against String Theory: 0.5%. Our current understanding of string theory doesn’t tell us which LHC-accessible models are or are not compatible with the theory; it may very well be true that they all are. But sometimes a surprising experimental result will put theorists on the right track, so who knows?
So, basically, the worlds greatest high energy physics experiment has a 0.5% chance to say anything abut the “leading” high energy physics theory of everything …
Maybe more is being said (by Sean Carroll) about this ToE than he realizes. This is an unbelievable admission of failure.
Aaron, what you say sucks, unfortunately it is also probably true.
Cheers,
T.
How long will it take to observe Higgs and Susy in LHC ?(in case they are at all present)
Aaron and Tommaso,
I agree. The answer is for more experimentalists to start writing books.
nbutsomebody,
There should be a FAQ somewhere…
I’ll recommend these predictions:
http://www.math.columbia.edu/~woit/wordpress/?p=882#comment-43559
We don’t know the mass of either the Higgs or the supposed superpartners. How hard it is to recognize these things depends on their mass. Many supersymmetry enthusiasts like models where the Higgs is low mass, and hard to see (a couple years or so required), whereas some superpartners are much easier, maybe could even be seen in data collected this fall (but probably not understood until some time next year).
We’re too busy doing physics
From the June issue of APS Physics,
I guess this is a bit obvious: but the days of being able to do significant fundamental physics experimets in your personal lab (or shed in the garden) seem to be gone. The LHC cost bilions. So, it is not suprising that theorists were/are involved in the PR for the LHC, and are needed to be vocal to gain funding: since it’s (suspected) benefits are purely theoretical.
Theorists are always the publicity seekers… Rutherford actually made contributions comparable to Einstein… Rutherford might even have contributed more… transmutation of elements, the structure of the atom, the proton, the scale of nuclear energies; also founding of a school that gave Chadwick, Cockroft, Walton, etc. But Einstein ends up being the man of the century, and Rutherford is forgotten (by the public).
The truth is that experimentalists are a little suspicious still of publicity seekers. George Smoot got hammered for `the face of god’, and Rubbia and Lederman long ago stopped being truly influential.
Peter or others, Now that LHC has started is the Tevatron still going to
continue running? Also does anyone know if people made bets about tevatron and what it would find
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Shantanu,
The US HEP budget situation is extremely unclear. The new fiscal year starts soon, and it may not be until half-way through it that there actually is a budget. As far as I know, plan is tor run the Tevatron through the next fiscal year, future after that depends on the budget and how the LHC does. As long as continued running makes it possible the Tevatron will see the Higgs before the LHC, I doubt it will get shut down. I don’t know of any Tevatron bets.
Of course Kaku is full of it in claiming that the LHC will find evidence of string theory, but what is really amusing is that he gets the physics of string theory wrong. The sparticles do not arise as higher vibrational modes of the string. If they did, they would be extremely massive and the LHC would never see them. The sparticles and particles of the Standard Model all arise as the lowest modes in superstring theory. Oh, and Kaku doesn’t make a living doing string theory. He makes a living writing popular science books full of wild ideas and outrageous claims.
Does this mean there is a small chance of the LHC producing Dragons? Won’t the black holes destroy them?
that sounds like an awesome movie.
The guy was writing papers on string field theory already in 1974, and got several hundred citations for them. He definitely has earned the right to call himself a string theorist, and a pioneer. There’s no point denying that.
But no matter what his credentials are, his predictions for the LHC are going to be as hard tested as anyone else’s. We’ll see…
Wouldn’t we consider either supersymmetry or large extra dimensions to be supporting evidence of string theory if either of them is observed at LHC? I know they wouldn’t prove string theory by themselves, but both supersymmetry and extra dimensions are central to strings.
The US HEP budget situation is extremely unclear.
The US federal budget situation isn’t so clear either. Let’s hope China and Japan don’t call in their chips.
Supersymmetry is important in string theory, but I’d say at this point that the connection between TeV scale supersymmetry and string theory is far from decided. Extra dimensions, on the other hand, are such a bizarre idea from a purely phenomenological standpoint, that I would consider them evidence for string theory although many extra-dimension theories these days are not obviously embeddable in string theory.
Karla,
Supersymmetry and extra dimensions at the LHC scale just aren’t predictions in any sense of string theory so can’t provide evidence for it. If either one is discovered, it won’t tell us whether string theory is right or wrong. On the other hand it will be a massive revolution in fundamental physics, with a huge amount to be studied and understood. If this happens, string theorists will try and see if string theory has anything to say about what exactly is observed and is able to make testable predictions. If they can do this, string theory will be revived, if not it will continue on its path to irrelevance.
Karla,
The discovery of extra dimensions would be a much bigger story itself than any confirmation of string theory . Extra dimensions would be a paradigm shift beyond even the Copernican revolution, IMO. There would be big questions opened up about
the universe ranging from the smallest to the largest scales.
So your question is ironic. But it does also hint at the extent to which the string theory people have warped the fabric of modern thought…..that is they have somehow established the “tacit” acceptance of extra dimensions as a “given” and proceeded to
build castles of sand upon that compacted nonsense.
Perhaps I’m just so old fashoned, but shouldn’t we first require the
string people to prove the existence of *one* extra dimension, followed by the verification of *eleven* dimensions, before anyone
would waste time to listen to their baroque ideas about what happens in those new dimensions?
What ever happened to doing science one step at a time?
Peter,
Sorry my post says essentially the same thing you posted….didn’t see your words until I hit submit. Anyway, thanks for your
continued important work and belated birthday wishes.
TW
Supersymmetry at .1% confidence is surely low. Its still the simplest and most natural solution to the hierarchy problem that we currently know off. Yes its bizarre that it hasn’t already shown up (either directly or indirectly), but it still has a nice parameter space to live in, and one which still leads to a satisfying solution as well as giving a dark matter candidate.
Putting it above 50% confidence is perhaps a little optimistic (nature loves tricking us), but something like 33% is still where i’d imagine most phenomenologists/theorists would end up averaging out too.
Hi,
yes, I think this hype could be really a problem. The successful start of the LHC has been broadcasted on ‘Phoenix’ (a TV broadcaster in Germany). A physicist from Bonn has been a guest in the studio of ‘Phoenix’. He mentioned again, that LHC will not be able to mimic the Big Bang. However the moderator didn’t ask further about this issue. What has been pointed out by the physicist was that the technology behind the LHC has been and will lead to valuable technology spin-offs. This seems to be really important.
When I talk with people about the LHC project, they are interested but often they want to know about the economic outcome of the experiments. I usually ask them, if they are not eager to know how the universe was born, or in other fundamental questions. I receive distinguished answers. I think people become somehow confused, since they obviously have other issues they are much more concerned about. No one can blame them for that, but this bothers me often. That’s because I often prejudge them, since I guess financial issues are these other issues. They seem not knowing that the technology behind the LHC is almost entirely extremely challenging and new, and that the knowledge that society is gaining through such a project is worth much more valuable than the money that this project costs.
Kind regards
Kay zum Felde
haelfix,
for my taste susy at 0.1% is just right. after all, it does not really solve the hierarchy problem, it merely ammeliorates it (or shift the fine tuning to other parameters as others might say).
saiko,
yes, that was in 74 and what exactly did he produce since then? i do not mean to be disrespectful, but there are a fair number of theorists even who would have much more of a standing to oped on a prestigeous journal than kaku. how about weinberg, gross or glashow? or yes, even greene for that matter, but who is kaku?
Peter,
I think you are obsessed too much with testable predictions. Surely this is what we want from a theory of physics which we regard a success. String theory is, as I think everybody would agree, work in progress. And so the only question is whether it is promising. The problem is that the answer to this question is subjective, although not arbitrary, because any opinion on that has to be qualified.
Surely discovery of supersymmetry and even more extra dimension would let string theory look more promising than today.
What would constitute evidence for extra spatial dimensions, as opposed to evidence (confirmation of) a prediction of a theory that happens to incorporate extra spatial dimensions? Is there anything like an unambiguous phenomenological characterization of evidence for extra dimensions, with little or no model dependence?
It would seem that compactified extra dimensions complicate the question considerably.
Mikael,
The problem with string theory is not that it doesn’t make testable predictions, but that the more we learn about it, the more it becomes clear that it can’t ever lead to testable predictions. If that’s an “obsession with testable predictions”, I guess I’m obsessed…
Peter,
what do you think of the work of Vafa presented at string 08?
He is trying to get at some phenomenolgy.
Mikael,
This is getting completely off-topic, but see
http://www.math.columbia.edu/~woit/wordpress/?p=697
What would constitute evidence for extra spatial dimensions, as opposed to evidence (confirmation of) a prediction of a theory that happens to incorporate extra spatial dimensions? Is there anything like an unambiguous phenomenological characterization of evidence for extra dimensions, with little or no model dependence?
Actually– and this is just my understanding from what I’ve read, so if I mess this up someone please let me know– yes:
The “mini black holes” prediction you see batted around as a long-shot possibility at the LHC is actually specifically a confirmation of “large extra dimensions”. The thing is that the LHC is not, in fact, running at high enough energies to create black holes; however, if there were large extra dimensions (where “large” just means “noncompact”) then there would be an effect where gravity is massively stronger over extremely short distances. This is because in a >4-dimensional universe gravity would follow not the inverse square law, but an inverse cube law or an inverse-256 law or something; however, it would also be the case that gravitons would be free to leak out into the above-4 dimensions, so past very very short distances this would smooth out into the normal inverse square law*. If this effect exists, then the difficulty of creating microscopic black holes is much lower, maybe low enough that the LHC would create them.
So if we see microscopic black holes at the LHC, then as I understand things this tells us there are extra noncompact dimensions; but it doesn’t by itself tell us how many dimensions there are**, and it doesn’t by itself tell us whether string theory is true. Of course since string theory provides us with a relatively rich working model of how and why our universe could be a 4D sliver in a higher-dimensional bulk, and nobody else I’m aware of in physics is predicting such a strange thing, then mini black holes would tend to be interpreted as proof of string theory.
* It isn’t clear to me whether this detail– the leaky gravitons thing– is something specific to and/or required by LED string theory, or if it’s just a general property of large extra dimensions scenarios.
** Although there’s been at least one paper suggesting that if a mini black hole were seen in a particle accelerator, observations of that mini black hole and its evaporation could be used to tell you various things about the extra dimensions that allowed that black hole to form. And of course being able to take observations of an actual black hole, ever, would probably tell us about quantum gravity in a few instants than we’ve figured out in a century…