This week’s string theory hype comes to us from USC physicists Clifford Johnson and Nick Warner, courtesy of the USC press office (see here and here). It’s garden variety hype of this kind, exactly the same claims about strings and extra dimensions that were being made thirty years ago. There’s no acknowledgement these haven’t gone anywhere, instead we’re “closer than ever to an answer”.
When the question of testability comes up, the multiverse is not invoked as an excuse. Instead, it seems that dark matter is going to provide the test:
Observations show that dark matter and energy constitute more than 95 percent of the universe. Scientists have established that they are new forms of matter and energy, but so far their precise nature is unknown. They may hold the key to confirming the veracity of string theory, Johnson said.
“It’s really kind of amazing — and humbling. There are forms of matter that seem to show up naturally in string theory that could well be good candidates to be dark matter,” he said. “People are hoping that this could be a key to making contact between theory and nature.”
Hard to know what Johnson has in mind for his “show up naturally in string theory” claim. Presumably he’s thinking of the ancient “we’ll test string theory by finding superpartners” claim, somehow neglecting to mention that this hasn’t worked out.
I’m especially impressed by the description of string theory’s power to explain dark matter as “amazing – and humbling”, deftly pairing outrageous over-the-top hype with an invocation of the selfless humility of the research scientist.
What are your preferred theoretical approach to the fundamental physics problems of dark matter and dark energy?
“The coolest thing about string theory is it’s the only theory out there that reconciles quantum mechanics and general relativity,” said Warner
What is not so cool is Warner’s complete ignorance of all non-string theories out there, that are at least equally as successful in this reconciling.
“There’s always the possibility that the framework is incomplete, or just plain wrong,” Johnson said. “We need a way of getting measurable predictions from the theory that we can go away and test — a key step in any scientific endeavor.”
At least Johnson can be ack-ed for not subscribing to ST-does-not-need-experimental-verification crowd. 🙂
About dark energy, I have no idea.
One thing I’ve never completely understood is the status of attempts to explain dark matter using right-handed neutrino fields. Such fields have no SM interactions, but there is a complicated story about neutrino masses, and it’s not clear to me you can’t get something massive that would explain the astrophysical observations, but would not show up in experiments designed to look for a very weak non-gravitational interaction. If anyone knows of a good source explaining this particular point, I’d like to hear about it. But I don’t want to try and moderate a discussion board about these topics.
Johnson pays lip service to experimental verification, but my experience in discussions with him is that his attitude is de facto the same as claiming this doesn’t matter at all. Back in the days of the string wars he wrote a long series of postings on his blog denouncing my book, and I tried then discussing with him the problems with “string phenomenology”. After getting some odd responses I finally realized his position was that such things were of no interest and didn’t matter (he also didn’t see anything incompatible between denouncing my book and Lee Smolin’s, and refusing to read them). From his latest, it seems to me his attitude hasn’t changed, as he deals with the connection to reality problem by repeating very stale hype that no one knowledgeable about the subject would take seriously.
The article begins with the oft used (exhausted?) analogy of a wire (or straw) to describe how extra dimensions might be elusively small. While I can begin to wrap my head around extra dimensions from a mathematical perspective, I’ve never understood what physicists hope to “see” probing finer and finer distances. Would they actually observe these dimensions? Are they looking for violations of conservation laws? Or would they observe motion in 3 spatial dimensions that can only be explained by invoking more?
I realize this question betrays my naivete and I don’t want to contribute noise to your blog, but any pointers would be appreciated :).
With reference to the Dark matter test of String theory:
They may hold the key to confirming the veracity of string theory, Johnson said
How is this claim justified without definite predictions from String theory?
I am generally far from your viewpoint but when I see someone describe some success as “humbling” the way Johnson does, that really irks me…and all the more so when it’s not even a success yet. What he should really find humbling is the number of typos in his book on D-branes.
What you expect to see depends on the details of what physics is governing your extra dimensions and how this interacts with conventional physics. A simplest example would be one extra dimension, a circle of some size with its geometry fixed. If you Fourier analyze, you expect momentum components in that direction to be discretized in units proportional to the inverse size. So, for very small circles, you expect to not see anything, until you get to energy levels that excite modes with those large momentum components. Then you will have a different energy-momentum relation, one involving those components.
But, there’s an infinite array of many other possible things you can do with extra dimensions to make them so far invisible, with new physics if you could see them. Many popular string theory books should have some more about this in the string theory context.
This is kind of off topic, note that even Johnson doesn’t think it’s plausible to claim we’ll see such things.
There are no string theory predictions about dark matter. One might think that Johnson was well aware of this, and thus being intentionally misleading. From my experience trying to discuss such things with him, I think it’s also plausible he just knows nothing about this beyond very old claims that string theory implies susy, and susy theories can have a dark matter candidate, hasn’t paid attention to the fact these haven’t worked out (or thinks that’s irrelevant and one is free to keep telling the public that some day they might).
To be clear. I’ve no idea what specifically Johnson is referring to as string theory “good candidates” for dark matter. Maybe he’s thinking of axions. I’ve never heard any other string theorist making this claim, though, so the whole thing is rather odd.
For sterile neutrino dark matter, see http://arxiv.org/abs/1204.5379 . I find nuMSSM particularly appealing, as you can also do baryogenesis with the right-handed neutrinos, all without introducing a new higher energy scale.
When I was touring graduate schools in the early 2000s I remember researchers at University of Washington working on a (more or less) tabletop experiment to test the 1/r^2 law of gravity at short distances. One of the motivators was that if there were extra dimensions and if they were large (much bigger than the Planck scale, but still much much smaller than the distances being tested) then there should be some deviation from 1/r^2. I never followed up, but I’m guessing they never found a significant deviation.
I don’t think Theoretical Physics is going to be able to get out of this Tailspin. Particle physics anyway. There’s no acknowledgement that the field isn’t even going anywhere, having been stuck in more or less a hamster wheel theoretically for, is it three or four decades now? The generation of people now retiring can hardly remember a time when the field wasn’t all about wild speculation and unsubstantiated results. I don’t think this is a situation a community or disipline can just “snap out of”.
The lack of progress is also pretty stark when you compare it to other fields in science and technology, which have in an understandable way made massive advances over the same period. At some point, especially if the LHC doesn’t make further discoveries, or a successor accellerator never gets built, I think this contrast may become too big to ignore and particle physics funding will dry up. Large colliders may go the way of the Apollo program, but unlike NASA will theoretical physics have enough wider support (or credibility) to be able to “keep the lights on” for a few lean decades. A lot of knowledge and expierience could be lost because the public got tired of hearing too much “fairytale physics”. Maybe this kind of “die-off” is actually what needs to happen to break the cycle.
Sorry for being so negative.
This kind of public relations effort from the USC string theorists does seem to be a response to the problem of people getting a clue that theoretical speculation (and especially string theory) has not been going anywhere for a long time. Unfortunately the idea seems to be to just have friendly media put out stories claiming all is well. This is of limited value in dealing with the NSF and other physicists, who may recognize empty hype for what it is. Perhaps the hope is that the public in general, and philanthropic billionaires in particular are not so savvy…
The experimental HEP situation seems to me quite different, with the LHC and the Higgs discovery definite recent progress. There the difficulty of getting to higher energy and the lack of new discoveries besides the Higgs are a looming problem, but a different one than that of having spent 30 years training students to work on unsuccessful speculative ideas.
Although it’s decades since I was an active physicist (optics) I am amazed and delighted be the progess in experimental physics, particularly HEP.
I understand the frustration than has come from the stagnation over the past generation in the apparent lack of productive theoretical physics. However, it’s a false premise to try to keep it alive by hyping failed theories…
I would add that also theoretical particle physics has been progressing in large strides, even if we ignore neutrinos, dark matter and other non-accelerator-related topics: calculational techniques have progressed hugely in the past few years: multi-loop calculations, many-body final states, model-independent approaches, automated calculations at NLO to name a few topics. The reality check the LHC provided has drawn brain capacity back from model-building (or model-concocting) to the tough work of doing actual calculations, and it’s showing.
Now you can claim that unlike a successful calculation in solid-state physics there are no applications, but then you are back to the question of why one should do fundamental research at all.
There are some ways to rephrase your observations in more quantitative ways:
1. There has been no Nobel prize to any discovery in theoretical HEP made after 1973.
2. When Frank Wilczek becomes 65 in 2018, there will be no active (below normal retirement age) “fundamental” theorist with a Nobel prize, for the first time since H.A. Lorentz won the prize in 1902.
It is of course possible that HEP theorists or even string theorists win a Nobel prize for contributions outside HEP; BPZ are my favorite candidates for their contributions to statistical physics. But with the possible exception of Zamolodchikov, they are also beyond retirement age.
See the most recent publications from the Eöt-Wash group. No detections of new physics.
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I wish Clifford Johnson (or his supporters) would defend his views here. As a layman, it’s hard to know whether I should believe Clifford or Dr. Woit.
For whatever reason, there have been no submitted comments here arguing that there’s a case for Johnson’s claims. He has his own blog, and way back when put out a long series of postings about criticism of string theory (which he characterizes as a Storm in a Teacup), see
Many of those postings have long and substantive arguments in the comments section.
Unless I’ve missed something though, I’ve never before heard this claim from him or anyone else about an “amazing” explanation of dark matter from string theory. It seems to be something he never used as an argument back then when other physicists were involved, but does think it’s a good argument for a popular promotional article.
Having just looked at this briefly, your description seems pretty unfair. It seems there is a write-up by a journalist of an interview? a chat? some kind of talk with Clifford Johnson in a cafe. It is a good thing that scientists tell other people what they are doing, but there is commonly some loss of transmission when filtered through a journalist with possibly no science background.
`Hype’ is putting out misleading press releases, not making genuine efforts to explain to a journalist aspects of a difficult and technical subject that are far removed from everyday life, and then finding that the non-expert journalist doesn’t quite get everything right.
This is basically a press release. The author is a “Public Communications Manager” working at USC. I think characterizing it as hype is quite fair, with the dark matter business especially egregious. It doesn’t even bother to try and explain what the USC faculty (Johnson and Warner) are currently doing.
I see no evidence that the writer is misunderstanding anything or getting anything wrong, rather that he is accurately transcribing the hype he was fed. For this kind of PR effort by a university, generally the faculty involved would be asked to look over the article before publication and make sure it is accurate.