No.
If you want to hear Cumrun Vafa’s latest “predictions of string theory”, there’s a podcast at Quanta magazine you could listen to. Over the years, Vafa has promoted various proposals for “predictions” of string theory. For instance, back in 2009 the Harvard Gazette reported on Cumrun Vafa briefs Large Hadron Collider scientists on string theory’s predictions. This was about some complicated, ugly scenario with no evidence for it that somehow could be sold as an LHC-testable “prediction of string theory”. Of course the LHC saw no such thing.
Here’s the podcast explanation of the latest complicated, ugly scenario with no evidence for it that is supposed to be a “prediction of string theory”:
Okay, so that’s the tiny dark energy. Now, as I just was telling you about, whenever there’s a tiny number or fine-tuned parameter in your theory, you should be asking what’s happening to these extra dimensions? Are they getting large or is there light string somewhere?
So already we are saying that having a dark energy, which is so extreme, must necessitate having new particles, where are they? On the other hand, we say there’s dark matter. So now we are saying that two facts, the fact that dark energy extreme and there’s some extra light particles around could naturally play the role of dark matter. So that’s the idea that already automatically comes from the swampland principles.
Now you can say, “Can we make it more quantitative?” It turns out that the dark energy predicts actually a length scale. And it turns out that length scale is about a micron. Micron is 1000th of a millimeter. And it suggests that exactly one of the extra dimensions is of roughly that size.
Now, you could ask then, what about the dark matter? Well, the dark matter would be the graviton waves, which were created in this extra dimension, what we call the dark dimension. So we have three spatial dimensions that we know, which are huge. One more dimension, which is this micron scale. And then the rest of them we think are much, much smaller.
So, therefore this one-micron dimension space will potentially carry in it some long gravity waves which would play the role of dark matter. So, in this context, we have a unification of dark energy and dark matter, just from this simple principle that when you have extreme values in your physical theory, there are light particles…
Because this tower of particles I was telling you about, which comes from these light particles has to be weakly interacting, which is the smoking gun of dark matter. It’s weakly interacting not only with us, but even with themselves.
So that is a property, it’s a prediction, I would say. So, we are making a prediction that whenever you have this dark energy being so extreme, you better look for light particles, which are very weakly interacting, just like our universe has it. So, this is a prediction for our universe.
And in fact, it makes another prediction: You cannot directly detect them because their interaction strength is gravitational. So, these direct dark matter detections will not succeed based on this study. So, we are making very specific prediction.
But actually you can make it even a stronger prediction. If you have two objects, two masses at the distance are, Newton taught us that there’s a gravitational force between them, which attracts them. And this force falls off with the inverse square of the distance between them. That is a property of three-dimensional space and one time. If you increase the number of dimension, each time you add one dimension, the power of the distance in the force law increases by one.
So instead of distance squared in three spatial dimension, if you have one extra dimension, it becomes distance cubed. And if you have more, it becomes distance fourth and so on. So, if we have one larger dimension, it should have been distance cubed. So, we are making a prediction that if you bring these objects together and put them at a distance roughly of a micron or so, you should find the stronger gravitational force between them.
This experiment to detect this is actually being undertaken now to bring it down from 30 micron perhaps to 10 micron and below to try to see if the force law changes as we are making a prediction. So that’s a very concrete prediction that we are making based on this link.
If you want to know what this is actually about, you could look at this, where you will read about a large number of different “predictions”, which somehow are derived from a grotesquely complicated scenario with no evidence for it which somehow is motivated by the swampland program, which somehow is motivated by string theory. As back in 2009, Vafa has a very idiosyncratic understanding of what the word “prediction” means.
You are an adamant opponent of string theory, so I thought I’d ask… do you feel there are promising alternatives to string theory right now? If so, which is your most preferred?
A return to physics is most welcome. Full respect for your public stand in support of your institution, but I think what is more fervently desired is some twistor news from you, it’s been a while since your last paper on the topic 🙂
Michael Zaal/tripitaka,
I have been making significant progress on the twistor stuff, trying to get a new paper finished. The more I look at this the more I’m convinced it’s a very promising new approach to unification (and thus an alternative to string theory).
The Columbia situation has been a serious distraction from that project.
Next week I’ll be at the Perimeter Institute for a conference in honor of Lee Smolin, looking forward to talking with people there about twistors and other things.
Michael Zaal,
I suppose I should also make this obvious point: string theory as a unified theory is a dead subject. Any alternative is better, at least in that it hasn’t been so intensively studied like string theory that you can be sure it can’t work.
As evidence for the above, many would argue that the sort of thing Vafa is promoting here is the most promising direction in string theory, but this is nothing but an extremely complicated and ugly model with nothing to recommend it. Just about anything is more promising than this.
Have you looked at:
https://iopscience.iop.org/article/10.1088/1361-6633/adc82e/pdf
It purports to be quantum gravity. Its in a place that I never heard of and has a suspiciously overly high impact factor
It looks interesting but I know enough about this that the words “its finite to one loop but we’re working on full proof of being finite” (paraphrased) are seriously ominous.
Its very spinorish.
Doug McDonald
Doug McDonald,
At the moment I’m desperately trying to find time to write up the twistor stuff, no time at all for things like this (or to moderate a discussion of alternatives to string theory).
Doug McDonald,
You can finds lots of similar articles purporting a new approach to quantum gravity (or to explaining the Standard Model, etc.) on arXiv every week, or even every day. I’m not sufficiently expert to know what’s missing or wrong in them. Many of them get published, somewhere. Heck, you can probably find some of them in fine journals such as PRD/PRL. Since none of them gain much traction, I assume they all have flaws apparent to experts at some level. Personally, I like the ’emergent gravity’ scenario, but that, too, has flaws. So I wish Peter good luck in his twistor approach!
You said: “As back in 2009, Vafa has a very idiosyncratic understanding of what the word “prediction” means.”
Will be very enlightening for the readers if you can be more specific so that they themselves don’t make same mistake.
vinay,
For most people, a “prediction” of a theory is something that the theory strongly implies will happen if you do an experiment. If you do the experiment and the “prediction” is wrong, there’s something wrong with the theory.
For Vafa’s “predictions”, there’s no real theory, no good reason to believe the “prediction” will be true if you do the experiment, and for him when the “prediction” doesn’t work, that’s in no sense a problem for the theory. What’s important is that you can tell people that it’s not true that your theory makes no predictions, that you have “predictions”.
I’ve wasted far too much of my life on this nonsense.
I find it stunning that this keeps going on even though at this point it should be obvious for anyone with half a brain that this is all nonsense research. They’re just making up some maths and, call it a “prediction”, and if that prediction doesn’t come true, they’ll move on to the next.
I can understand that 20 years ago when some of us started pointing out that this isn’t proper science most people were skeptical. I get it. People who don’t have a background in the area don’t want to make judgements about it because they’re afraid they just don’t understand enough of it. Ok.
But now? Like, how much more evidence do you need that this isn’t proper science?Just look at all the alleged “predictions” that have been falsified.
And it’s not like this is only old people who continue what they’ve been doing, there are still new people getting into this. It’s still going on!
Doug McDonald, RPP is a long-established review article journal – it’s basically the IOP’s version of Rev Mod Phys. It has a high impact factor because good review articles tend to be highly cited. Rev Mod Phys consistently has an impact factor of around 45.
Sabine,
I don’t think describing what Vafa is making up as “some maths” is really right. If you look at
https://arxiv.org/pdf/2402.00981
the equations rarely even have equal signs, lots of tildes, some inequalities. This is pre-scientific, pre-Newton, mathematics at the Babylonian level of development.
There really is no theory here, just an obsession with bogus claims about “predictions”, which we’re told are “concrete”, “unique” and “very specific”. We’re also told that it will be “exciting” either way. If the predictions work string theory is proved since some inequality motivated by it is satisfied, if they don’t work, we’ve learned something new about string theory! The hype level is out of control, full of pre-scientific reasoning. It gives up on the whole idea of using mathematics to both make precise conjectures about the real world, and from these conjectures derive observable consequences.
“… mathematics at the Babylonian level of development…”
Actually, the Babylonians were rather sophisticated:
https://en.wikipedia.org/wiki/Babylonian_mathematics
They needed to understand things like seasonal flooding, and make (what’s that word again? oh yeah…) predictions to prepare plantings and feed their society. I think this is more of a Trumpian level of mathematical development.
@CWJ “Since none of them gain much traction, I assume they all have flaws apparent to experts at some level.”
I wouldn’t necessarily assume that. It’s just that there are so many of these vague ideas that hardly anyone in the field even has the time to thoroughly read these papers, not to mention do some meaningful work on it. It’s just not a rewarding thing to do: it’s usually hard and time consuming to get something publishable out other people’s idea and most of the time you will just find that it doesn’t work in the end.
If you want to publish papers (and thus stay in the queue for a tenured position) it’s much easier to come up with your own very speculative, likely wrong idea, and just do some superficial calculations at the surface – most of them you will get published somewhere with a bit of effort and once you get there, it’s usually easy to get a few follow up papers, since you already know the stuff and rarely have any real competition (as nobody else has time to care about your ideas either). But then you have to move on to the next crazy idea before getting too deep into something, where you would need to do some actual, time consuming and hard work that will put you behind in the publications game. So none of these ideas ever really get worked out in detail.
I wouldn’t be surprised at all to learn, one day, that the right idea has been out there all along in some ominous paper in some low-tier journal that only the authors, and with some luck the referees, have ever read.