This week in Madrid there’s a conference going on with the title Why mH= 126 GeV?. It brings together HEP theorists working on “Beyond Standard Model” physics, with the majority of the participants from Western Europe, especially Spain. As part of the workshop they did a survey, getting about 50 responses. Among the results:
- For the question “Do you think that String Theory will eventually be the ultimate unified theory?”, 27% said Yes, 73% No, with the Nos breaking up into 27% just “No” and 46% “No, but it is a step in the right direction”.
- For a question about the hierarchy problem, the three opinions that got the highest numbers were pretty much split evenly among them: “Low energy SUSY solves the problem”, “Anthropics solves the problem”, and “There is no such problem.”
- Opinion was evenly split on whether the LHC would or would not find non-SM behavior of the Higgs, and 60-40 in favor of the LHC finding some non-SM new physics.
If you’re at all interested in what the current mood and thinking is in this part of HEP theory, you should definitely take a look at the video of this evening’s discussion section, moderated by Joe Lykken. It included extensive debate about the questions raised by the survey and what people’s answers meant. At the end there was a short interesting discussion about AdS/CFT and its relation to string theory, with Michael Douglas arguing that AdS/CFT should be thought of as an improved version of the renormalization group, with no necessary connection to string theory. String theory and SUSY only come into it by providing certain examples where you can do explicit calculations in the dual theory. By the way, I’ve heard a rumor that Douglas is going on leave from his physics job to work at the Simons hedge fund Renaissance Technologies.
Among the talks so far on-line, you might want to take a look at Alessandro Strumia’s Is Naturalness Natural, for an example of the sort of thinking that denies the dichotomy of “low energy susy or anthropics”. As the survey showed, this insistence on other alternatives has at least 1/3 support, and Joe Lykken mentioned that he was in this category.
Michael Dine’s talk on Alternative Futures for Particle Physics starts off with slides about Neil Turok’s comments on the “crisis” in the field, and shows this blog entry. He then goes on to give a string theory landscape/anthropics-based point of view on prospects for BSM physics. At the end of the talk there’s some pushback from the audience, with one questioner describing Dine’s anthropics as “a kind of sleeping pill, so you convince yourself that you are smart”, calling this “theology” not physics.
Dine describes my blog entry he showed as one that personally insults him, something that certainly wasn’t intentional. He’s not mentioned at all, but I gather he’s unhappy about my description of the material in the slides of Sally Dawson’s HEPAP presentation
Dine was chair of the committee that produced this report on The Future of U.S. Particle Theory and it’s well worth reading for a detailed overview of the current state of HEP theory research in the US, especially from the more phenomenological end. Like the slides though, I’d describe it as mostly avoiding dealing with the intellectual crisis that Neil Turok was describing. Even though Dine was the chair of the committee, there’s nothing in its report about his favored road ahead (the landscape and anthropics). I’d guess that the committee members felt that when trying to get support for HEP theory from other scientists or government funding agencies, talk of crisis-level problems with conventional wisdom was to be avoided, but even more so any mention of the string theory landscape and anthropics.
Update: For the latest on the landscape, see Michael Douglas’s talk on The string landscape and low energy supersymmetry. At the beginning of his talk he notes that “most people seem to have given up” on this, and from the talk itself it’s easy to see why. Actually, Douglas himself seems to be giving up. I’ve heard more about his move from physics to finance, which began last fall when he went on leave to work at the Rentech hedge fund. Evidently this fall he is not coming back to the Simons Center, but staying at Rentech, leaving his academic position. Rumors are that one reason he gives for leaving is that there is not much of interest going on in HEP theory these days.
Michael Douglas is right about AdS/CFT. The idea of holography is quite general and doesn’t require string theory. It can also be realized entirely within quantum field theory where you can show that a topological field theory (which is similar to a gravitational theory since it is “generally covariant”) can be equivalent to a conformal field theory on a lower number of dimensions.
Hi Peter,
This isn’t the first time I’ve heard that AdS/CFT is independent of string theory (which seems true from what I know, but I don’t feel qualified to rule on that), but the first time I’ve heard that it should be thought of as an improved version of the RG. Do you know any more detail about what he means there?
The almost inconsistent SM parameters have an interesting analog in statistical physics. In the 1940s Onsager showed that critical exponents have to satisfy certain inequalities. Twenty years later people realized that these inequalities are in fact equalities, i.e. critical exponents are on the border of inconsistency. The underlying reason is scale symmetry.
By analogy, the fact that the SM Higgs mass is on the verge of inconsistency could be a sign that a symmetry principle is at work here too. If so, there probably isn’t any BSM physics to be found, apart from gravity which is a different matter altogether.
Hence the null results from the LHC could actually turn out to be quite exciting.
@Peter Have you seen the recent blog post by Andreas Karch in Lubos’s blog? http://motls.blogspot.com/2013/09/guest-blog-on-applications-of-holography.html
Any thoughts?
Ray,
Well, one thought is “why would anyone sensible want to appear as a guest on Lubos’s blog?”…
But, beyond that, seems like a reasonable discussion, although just dealing with one side of the story, reasons for optimism about doing things with this set of ideas. If you want to discuss it though, you really should discuss with Karch, not me.
CU Phil,
I’m not sure exactly what Douglas had in mind, but in AdS/CFT, the fifth dimension has an interpretation as an energy or distance scale, and people have used that to discuss various ideas about a “holographic renormalization group”.
Peter,
Thanks for pointing these talks and videos. A lot of the talks seem to say that there is already evidence for fine tuning or unnaturalness at 1% level (some even have it at 0.1%). That is pretty interesting. Maybe after a few years of data from its 14 TeV run, LHC can establish fine-tuning at a 0.1% level…
0.1% fine tuning wouldn’t be completely implausible in the context of the “dimensionless factors should be ~1” naturalness argument. Would something like 1/(8pi)^2 show up on anyone’s naturalness radar?
Peter thanks for the link to this video. extremely interesting.
Joe Lykken seems to agree with you about string theory. The discussion about inflation and quantum gravity was also quite interesting.
I disagree with Slava that there is no alternative to inflation.
If you liked the survey, please post your own answers at the comments thread of my blog post on the matter, here: http://www.science20.com/quantum_diaries_survivor/confidence_new_physics_and_susy_dropping_stone-121294 . And specify whether you are a particle physicist… It would be nice to compare the views of HEP physicists and the rest of the world !
T.
Douglas’ propositions regarding AdS/CFT and HS gauge theory are weird at least. HS gauge theory is String’s theory backyard and can be only understood only as a limit of it.
For an analysis on a conceptual level of the gauge/String correspondence the interested reader is redirected to the following classical paper by Polyakov:
http://arxiv.org/abs/hep-th/0110196
@Giotis String theory is also argued to be a spontaneously broken phase of HS theory.
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It’s still String theory which possesses this HS gauge symmetry i.e. its tensionless limit; the tension generation breaks the symmetry and the tensile String theory emerges.
I’d say that some degree of congratulations is in order, Peter. The rats are starting to abandon Hook’s fantasy ship in droves!
I’ve heard a rumor that Douglas is going on leave from his physics job to work at the Simons hedge fund Renaissance Technologies.
Yay for Stony Brook’s anchor firm!!
Dear string theorists: Your field is dying. Come to Long Island and work in quantitative finance while you figure out your next career move! 🙂
great title, “why higgs mass is 126 GeV?”; i like this way to organize workshop! next ones could be, why omegaLambda=0.692, why theta13=9 degrees, and many more to follow… we have a lot of useful occasions of discussion, why we speak of a crisis of HEP? (that could be another title, in fact)
All those bright theoreticians going into finance is genuinely scary. Not only will finance have more capital and political power than everyone else, but no one else will be able to understand what they are doing. Not only tougher, but also smarter than the rest of us. Something like “chess-boxing” masters. Resistance is futile.
🙂
Pretty much! But since both quant finance and string theory are basically just ways for us to keep our smartest people active and occupied until we have something useful for them to do, we might as well have the smart people make money while they wait! 😉
>Implying that finance understands what it is doing in the first place.
I think the people taking pleasure in this rumour about Douglas are being moderately nasty and entirely misguided. In a field that is subject to lots of hype, Douglas has always struck me as a very honest, level-headed, sound physicist.
CU Phil,
I agree that personal criticism of Douglas is out of line. With string theory unification stuck in the dead end of the landscape, it’s eminently reasonable for him to decide he’d rather do something quite different with his life. What he’s doing is actually a lot better for the field than sticking around not doing much in a permanent position, since it opens up a job for someone else. One could criticize on scientific grounds his decision to promote (and continue promoting as in his talk) the string landscape as a viable rather than dead idea (and I have), but that’s a scientific, not personal criticism. The world is full of wonderful, admirable people who I happen to disagree with about something or other.
Hi Peter,
FWIW, I wasn’t talking about you. You’ve always seemed to treat Douglas as an honest, well-intentioned guy who you happened to disagree with. It was people celebrating this as “rats abandoning the ship” that irked me — even if that was something to be celebrated, the ship seems to be better off with people like Douglas than without them.
So there are people who know better than the smartest people what the smartest people should be doing – but they are not themselves the smartest people – ? That sounds like a contradiction. There are different kinds of smartness. Although I had little success in getting academic posts, in 1984 I was at least smart enough to see that String theory was a blind alley. If more theorists had shared my insight a huge waste of time and effort would have been avoided. In the area of quantitative finance, any market professional could have told the quants building models that repackaged sub-prime mortgage bonds to create AAA tranches from junk – a group that, on paper, looked incredibly smart – that the models were fundamentally flawed because diversification cannot be used to reduce risk in volatile markets as in these circumstances all correlations become either 1 or -1. See The Big Short by Art History major Michael Lewis for a good analysis of this. So in this situation too the “smart people” did something seriously not bright.
“For a question about the hierarchy problem, the three opinions that got the highest numbers were pretty much split evenly among them: “Low energy SUSY solves the problem”, “Anthropics solves the problem”, and “There is no such problem.”
I am surprised by the fact that so many indeed believe “there is no such problem” since I haven´t seen any prominent theorists defending this point of view. I guess it is the sort of thing people secretly think for themselves but fear criticism of people in the high chain of command (like Arkani-Hamed). With the LHC results and the pressure on SUSY, I guess maybe people will begin to speak more freely about it.
In fact I know of no good paper (a review would be particularly useful) that discusses this particular point of view. I am curious to know if others do (if so, please share).
(disclaimer: I have no intention to discuss the hierarchy problem per se here for the thousandth time).
“In the area of quantitative finance, any market professional could have told the quants building models that repackaged sub-prime mortgage bonds to create AAA tranches from junk – a group that, on paper, looked incredibly smart – that the models were fundamentally flawed because diversification cannot be used to reduce risk in volatile markets as in these circumstances all correlations become either 1 or -1. ”
It WAS incredibly smart. The quants and the market professionals and the rest of those pigs made incredibly big amounts of money, and everyone else got incredibly screwed and had to pay for it. And then we had Derman telling us how he never, ever even suspected that, as a quant, he was not working for Eleanor Roosevelt, and how shocked – shocked! – he was to learn that not all the profits were going to UNICEF.
How inspirational was that!
Please, enough generalized finance bashing, which is pretty much off-topic (no, whatever you think of Renaissance Technologies, they weren’t responsible for the mortgage-backed securities mess).
Anonymous —
In MSSM that solves the hierarchy problem, it is factors of order 1 (or for some terms maybe of order 0.1) that multiply SUSY breaking scale terms M_SUSY^2, to give the contribution to Z mass (m_Z ~ 100 GeV). If M_SUSY becomes order 1 TeV this is 1% fine tuning (~m_Z^2/M_SUSY^2) and if its 3 TeV its 0.1%.
The naive 1/(8 \pi)2 factor which is in front of the Planck scale (UV cut off scale) in standard model for estimating quadratic divergence due to loop effect, does not multiply the scale that is expected to solve the hierarchy problem.
What I am saying is, even if it turns out that the MSSM is a correct effective theory of nature, it would remain mysterious why SUSY had to be broken at all. A more enlightened theory might be able to show that, ah, of course, it must be the case that “m_Z = m_SUSY/8pi” (or something like that; I mean a theory that can relate m_Z and m_SUSY perhaps in the style of the relation between m_Z and m_W in the SM), explaining the breaking and resulting in the apparent “fine tuning” of 1/(8pi)^2, which would not be fine tuning at all, being a very reasonable not quite ~1 constant.
The argument is intended to be that 0.1% fine tuning is equivalent in my eyes to 50% “fine tuning”, because mundane constants like 1/(8pi)^2 are no less “natural” (dimensionless constants are naively expected to be ~1…) to me than 1/sqrt{2}, say. Heck, even 1/(64pi)^4 doesn’t ring naturalness alarm bells for me (again, I can easily imagine that some future theory could show that SUSY breaking must lead to exactly this level of fine tuning). My standard for natural is “is it conceivable that a future theory predicting a relation between these parameters, which today we must take to be free, would give such a small ratio”. I have pretty low standards for that threshold.
So there are people who know better than the smartest people what the smartest people should be doing – but they are not themselves the smartest people – ? That sounds like a contradiction.
Not if you believe in the “wisdom of crowds”… 😉
Anonymous — This does not happen in MSSM but in principle there could be some new solution to hierarchy problem where there is a small coefficient like you say between the scale of new physics and the weak scale and then there would not be fine-tuning — but I dont think such solutions have been found yet.
If nature actually uses such a solution, I think it would probably apply directly to standard model (SM) without need for SUSY….so it does not require one solution of the hierarchy problem (namely, SUSY) to lower the Higgs mass down from Planck scale to SUSY scale and another solution between SUSY and weak scale.
It would be very useful if someone came up with a mathematical proof that within the framework of the usual QFT and SM, the solution for hierarchy problem must be at the weak scale or else there will necessarily be fine-tuning.
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Relative to factors or 2 and PI and sqrt(2) etc..I recall Sidney Coleman recalling in a lecture that in his oral of some some sort he attempted to wave his hands at such factors…only to have one of the committee (R.F. for short) say to the young Sidney: “If you don’t understand where the 2’s and PI’s go…you don’t understand it at all.”
The argument for the existence of the hierarchy problem essentially assumes we roughly know the Bayesian prior probability distribution on the parameters of the QFT. If we believe that the Standard Model (and any low-energy extensions of it) is just an effective field theory, and we don’t know anything about the underlying structure, then all this discussion of fine-tuning and the hierarchy problem is highly speculative.
Peter Shor,
While finding your argument quite interesting, I am not sure I follow it completely (my gut feeling is that I´m not alone). Any reference where this is discussed a bit more detailedly?
Dear Peter,
I agree with what you say, and I would add that since any pdf chosen as a Bayesian prior depends on the choice of variable (it will change by the Jacobian if we change variable), that choice is a further assumption one is implicitly casting into the problem.
Cheers,
T.
“The argument for the existence of the hierarchy problem essentially assumes we roughly know the Bayesian prior probability distribution on the parameters of the QFT. If we believe that the Standard Model (and any low-energy extensions of it) is just an effective field theory, and we don’t know anything about the underlying structure, then all this discussion of fine-tuning and the hierarchy problem is highly speculative.”
Well, sounds reasonable, but tuning arguments are very much common-sense ones, and they have been successful previously in a number of well known cases. Your criticism would apply equally well to those.
Tommaso,
Would you consider writing a blog entry about this? The hierarchy problem is one of the most taken for granted problems in HEP, with little to none questioning about its validity. I must say that I have been searching for papers discussing just what it´s being stated here, without success.
After I read your comment, Peter Shor´s comment was suddenly clearer, but I (and I believe many) would benefit from reading your take on this. As you know, let not overestimate most physicists knowledge of statistics which I am sure is, on average, way below yours.
Just an idea, think about it….
Bernhard, you can read this: arxiv.org/pdf/1307.7879.pdf
Is the clearest and sharpest you can find.
anonymount,
Many thanks!
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