At the big annual APS meeting, now going on in Jacksonville, of the 9 plenary talks, one is about particle theory. The talk is entitled “String Theory, Branes and if You Wish, the Anthropic Principle” and it was given by Shamit Kachru of the Stanford group. Here’s the abstract, which besides the usual claims that string theory is “our most promising framework for a unified theory of the fundamental interactions” and that “the underlying theory is unique”, also makes the claim to have “testable ideas about inflation and particle physics”. No clue what these ideas are, so I don’t know if they include the testable prediction the landscape makes about the proton lifetime. Also unclear why the Anthropic Principle is being demoted to “if You Wish”. Lots of experimental talks on particle physics at the conference, here’s a Fermilab press release on CDF and D0 results discussed at the meeting. Lawrence Krauss was speaking on “Selling Physics to Unwilling Buyers”, I wonder what that was about. More about the meeting at the Physics Meetings blog.
David Ben-Zvi has put up on his web-site his lecture notes from last week’s series of lectures in Oxford on geometric Langlands. As usual, a very readable survey of the subject, emphasizing links to representation theory.
For another source of material about representation theory and the (non-geometric) Langlands program, see the web-site hosted by the Clay Mathematics Institute devoted to the collected works of James Arthur.
There’s yet another round of discussion on bloggingheads.tv between science writers John Horgan and George Johnson. This week the LHC and the state of particle physics are some of the topics they consider.
From Fermilab, various new sources for discussion of the future of experimental particle physics include:
A web-site for the steering group tasked with developing a roadmap for future use of US accelerators. This week’s meeting includes a presentation on reconfiguring the Fermilab accelerator complex to produce larger numbers (factor of 3 more) protons, for use by neutrino experiments and others.
The Fermilab Physics Advisory Committee met on March 29-31, here are the presentations and report.
Last week there was a workshop devoted to considering what effect early data from the LHC would have on plans for the ILC (via Tommaso Dorigo).
Finally, Steven Miller, author of “String Kings”, has a new blog he is working on, devoted to essays on mathematical physics, theoretical biology and the history of science.
Update: Two more.
Seed magazine has a series of “cribsheets” about science. For physics, they cover nuclear power, the elements, and now string theory. The lack of predictivity of the theory is given a positive spin as being due to the “rich diversity” of string theory. At Cosmic Variance, Sean Carroll approvingly refers to this as “it only refers glancingly to the anthropic principle, which is a much more accurate view of the state of discussion about string theory than one would get by reading blogs.”
Nature has an article about the state of the LHC and the possibility that the Tevatron might be the first to see the Higgs. LHC project manager says that they were already running about 5 weeks behind schedule before the problem with the quadrupoles appeared, but says “In my view the magnet problem has been blown out of proportion… It is a very small part of a bigger picture.” If the schedule slips much more, there might not be time for an engineering run in 2007, and the first science run might be delayed until later in 2008.
Update: Thanks to commenter F. for pointing to the slides from Kachru’s talk. It’s a clear presentation of the moduli stabilization problem and the techniques that he and others used to solve it, while at the same time making the landscape problem much worse. The “testable” ideas mentioned in his abstract are the usual sort of thing behind claims like this: not actual tests of string theory, but effects in certain very specific models among the infinite variety of ones you can get out of string theory. Kachru doesn’t much address the issue of whether the landscape framework is testable science in the conventional sense, other than to describe people’s attempts to use eternal inflation to explain how the vacuum gets selected and try and get physics out of this as “notoriously confusing.” He also describes counting of vacua as favoring high-scale supersymmetry breaking, so maybe there is a prediction: no supersymmetry at the LHC.
Update: For the latest from FNAL on the LHC magnet problems, see here.
Peter,
“No clue what these ideas are, so I don’t know if they include the testable prediction the landscape makes about the proton lifetime.”
Would you ellaborate on that? The landscape makes an experimentally testable predition?
Best,
Tim
Tim,
One of many problems with the anthropic landscape is that conservation of baryon number is rather special, typical vacua will have baryon number violating interactions. The bounds on the proton lifetime are something like 10^32 years, whereas, anthropically, all that is needed is for only a small fraction of protons to have decayed since the big bang (10^10 years ago). So, unless you can find a landscape argument for why the GUT scale has to be so high (and I don’t know of any) protons should decay much, much faster than they do in the real world. The landscape folks seem to take the attitude that they can claim “testable predictions”, while ignoring the fact that similar or even better grounded “testable predictions” of the scenario are already falsified.
Peter,
Proton decay experiments have falsified SU(5) and SUSY-SU(5), I am unsure about SO(10), but if GUT as a class are all falsified, whether through proton decay experiments or lack of monopoles, would this falsify stringy unification scenarios, or for that matter, the need for SUSY in GUT unification?
Thanks
Dan
dan,
I don’t think you can falsify GUTs as a class, since you can always find models with longer proton lifetimes than can be measured, in particular this is true for some SUSY-GUTs. In stringy unification scenarios you can get any proton lifetime you want, so, again, you can’t falsify these.
What you can falsify is the idea that we’re at some generic, anthropically allowed point in the string theory landscape, and this has already been falsified by not seeing proton decay.
Hi,
thanks for answering my question. I infer though that all stringy unification scenarios are extensions of GUT scenarios, which may or may not be physical (and the simplest sort, SU (5) and SUSY (5) has been ruled out).
Dan,
Because SU(5) has been ruled out, it is at least wrong, which is a whole class better than the not even wrong status of string based unification, where there’s a landscape of theories too big to ever rule out. However, the way that some unification schemes can be fiddled to keep falsification at the door, is familiar:
‘Many physicists are working very hard trying to put together a grand picture that unifies everything into one super-duper model. …
‘Somebody makes up a theory: The proton is unstable. They make a calculation and find that there would be no protons in the universe anymore! So they fiddle around with the numbers, putting a higher mass into the new particle, and after much effort they predict that the proton will decay at a rate slightly faster than the last measured rate the proton has been shown to decay at.
‘When a new experiment comes along and measures the proton more carefully, the theories adjust themselves to squeeze out from the pressure. … The phoenix just rose again with a new modification of the theory that requires even more accurate experiments to check it.’
– R. P. Feynman, QED, London, 1990, p150.
This is the interim step between definitely falsifiable theories, and definitely unfalsifiable stringy M-theory. It must be a sociological issue. Mainstream physicists didn’t want to risk to their careers of being experimentally refuted after working on and popularising a falsifiable theory, so in the 1980s they started getting excited about theories that were increasingly ‘safe’ from experimental tests.
The usual claim that extradimensional string theory started out with the hope of being checkable but gradually the initial optimism has proved exaggerated, is maybe bit too kind to the string theorists. It didn’t have any experimental evidence at the beginning, just a lot of hype and ‘hopeful possibilities’ (which isn’t worth a dime in science, where facts alone count and hope is just faithful religion).
Peter,
what do you think of this?
John,
I’d really like to avoid turning this into a forum to discuss very speculative ideas like Sparling’s, this is something I don’t have the time or energy to moderate and would quickly get out of control. A couple quick comments though: in general I think the idea of using twistor geometry is promising, it is a very fundamental idea about 4-dimensional geometry. I haven’t looked yet to see exactly what Sparling is doing, but all attempts like this I’ve seen in the past don’t reproduce the standard model QFT set-up. My feeling is that you need not just the typical kind of kinematical idea about finite-dim symmetries that people are trying, but some new insight into the structure of gauge theories that would make non-trivial use of spinor geometry.
It must be a sociological issue. Mainstream physicists didn’t want to risk to their careers of being experimentally refuted after working on and popularising a falsifiable theory, so in the 1980s they started getting excited about theories that were increasingly ’safe’ from experimental tests.
I often find such statements disturbing. In the same line, it has been argued elsewhere that string theorists have invested their whole careers in string theory and with the lack of experimental confirmation (or lack of predictability, for what is worth) they are making use of desperate arguments like the anthropic interpretation for the landscape, as a new shift in paradigm of the scientific method, etc.
Well, what sounds odd to me is that there is a basic principle that any scientist learns very early: failure is much more common than success. Or, better yet, as Thomas Edison have (presumably) said:
Whether string theory will turn out to be right or not, is not the problem here, but simply the fact that one should not make claims in advance before effectively succeeding. So, if some string theorists are doing such a thing, yes, they would be wrong in a very basic sense.
On the other hand, independently of making anticipated claims or not, if things look bad enough so that there is a possibility that string theory will not be successful, that would not be the case for desperation.
What, if a scientist fails? How much is that bad? It’s part of the game!
Winners x losers is a strong paradigm of the american society, and I often find it funny from my latin american perspective. Yes, it can lead to useful achievements in some aspects, but not always. But it makes no sense to see scientists as winners or losers. Great scientists had their moments of discovery and failure.
So I can only conclude that the problem stands on the following general basic issues:
1. You should never make anticipated promises in science. Things might work, or might not, and the latter is much more common than the former.
2. In science, there are no winners or losers, but the advancement comes, in general, from brilliant people, clever experiments, incremental work, some luck and opportunity windows, failure (yes!), and, finally, (using another quote from Edison):
The bottom line is a very obvious thing: any good scientist does not fear failure, does not make anticipated claims, and are not winners or losers. They’re are just… scientists.
I do not have doubts that there are many good scientists working in string theory. So I can only agree that the sociological issue has a share of importance in the whole issue, which, for what is worth, will be very interesting from the point of view of the history of science.
Christine
Christine,
I agree that most scientific research is speculative and ultimately won’t work out. So people should be expecting to spend most of their time on ideas that will fail, or lead to very modest advances, and there’s nothing wrong with this. The problems people are addressing now in particle physics are extremely difficult, and one should expect essentially everything one tries to not work. What bothers me is that I don’t see people trying a lot of different things, and giving up on ones that don’t work. Instead, effort continues to pour into a narrow range of ideas, especially string theory, even when a huge amount of evidence has accumulated that the idea of getting a unified theory out of a 10 or 11 dimensional string theory is inherently unpredictive and can’t work.
This seem to me to involve two big questions which I don’t think are being addressed, a positive one and a negative one:
1. How do you encourage people to try something new, different than what other people are doing, given that it is most likely to fail? Can one provide incentives so that young people do not feel that they are probably committing professional suicide when they try and do something new and ambitious?
2. How do you get people to acknowledge that an idea that they have a huge amount invested in doesn’t work, once it becomes clear that this is the case? In the past, experimental results provided discipline of this sort, now we see a whole field devoted to ideas that inherently cannot be confronted with experiment, and thus are immune to this kind of discipline.
‘How do you get people to acknowledge that an idea that they have a huge amount invested in doesn’t work, once it becomes clear that this is the case?’ – Peter Woit
You can’t do that. If people are irrational enough to believe in an elaborate guess which just interconnects assorted speculative unobservables (gravitons, supersymmetry, standard model unification at near Planck scale energy), without any connection to observables, and without any hope of making falsifiable predictions from the landscape, it won’t be possible to get them to give up!
It’s like trying to debunk religion or UFOs, it can’t be done because there’s no evidence to be discussed, there’s nothing physical to be scientifically examined. In a free country, people are entitled to believe in failed theories, crazy ideas, and whatever they want. The basis of the problem is groupthink, is the illusion that because it has a lot more people than alternatives, you get the the ‘so many people can’t all be wrong’ dogma being used to defend the mainstream, despite the lack of science. The only way they could be defeated is by losing research grants, with the media ignoring their arrogant, unsubstantiated claims.
Dear Peter Woit,
Yes, the two points you make are important.
1. The system must definitely be reformulated. Negative results are results. Lessons learned are results. New ideas should be incentivized up to the point that they can be scrutinized by the scientific method. Number of papers cannot be taken as the absolute measure of a scientist’s achievement.
2. Such an acknowledgement must arise from two fronts: an internal one, in which a good scientist will eventually reach at, and from an external consensus, which depends on how the system is structured (item one above).
However, these are simple views that I have, from a simpler world. I understand the issue is in reality much more complex than the solutions above suggest.
Christine
Christine: you said Number of papers cannot be taken as the absolute measure of a scientist’s achievement.
A noble aspiration. Regrettably, the real world does not work that way.
Sorry if I come across like a cynic. But I’m old enough to be allowed to be one.
But I respect your idealism.
Peter,
You wrote:
“One of many problems with the anthropic landscape is that conservation of baryon number is rather special, typical vacua will have baryon number violating interactions. The bounds on the proton lifetime are something like 10^32 years, whereas, anthropically, all that is needed is for only a small fraction of protons to have decayed since the big bang (10^10 years ago). So, unless you can find a landscape argument for why the GUT scale has to be so high (and I don’t know of any) protons should decay much, much faster than they do in the real world. The landscape folks seem to take the attitude that they can claim “testable predictions”, while ignoring the fact that similar or even better grounded “testable predictions” of the scenario are already falsified.”
Now I’m at a complete loss regarding your point of view. You published a book as well as hundreds of blog postings about string theory and landscapeology being ‘Not Even Wrong’ because no testable prediction emerges from these ideas. At the same time you acknowledge that there is an experimentally testable prediction from the landscape (right or wrong, doesn’t matter at this moment).
You changed your mind? Or what’s going on? Why not change the title of the blog to ‘Wrong’ from ‘Not Even Wrong’ if your motivation for the title is the lack of an experimentally testable prediction? Will you release an errata to your book?
Please explain what you think about these matters because until now I went into great pain of understaning what you really mean and just when I thought I get your point (with or without agreeing with it, that doesn’t matter at this moment) I’m just completely lost again as to what the heck your message is.
Best,
Tim
But I respect your idealism.
Thanks. And I am sure I’m one of the last idealists living today. 🙂 Enjoy yourself!
In any case, it is really difficult to have an objective measure of a “good scientist” or the potential of a young researcher, something that you can only (in general) have some judgement in a posteriori cases or when you work closely with that person. So it’s more a question of acknowledging these fragile points and to decide whether one is willing to take some risks and incentivize diversity or other means as a possible paradigm for a healthy scientific activity. This is something I tend to agree with Smolin.
One other thing is the question of being very precise in defining the status of one’s subject of investigation. One should be extremely careful in making use of some established convention that specifies what a theory (with “T” or “t”, whatever) is, what a hypothesis is, what a set of conjectures is, what a model is, what an idea is, etc. I believe these terms are at some level reasonably distinguishable, but sometimes are used indiscriminately under different meanings in papers, talks, etc. In this respect, I think that the high energy community should attempt to reach a consensus on the status of string theory. Somewhat in analogy, astronomers met and changed the status of Pluto as no longer a planet as it was realized for some time that it did not fit the convention of what a planet is.
Christine
Tim,
The point is the following: the landscape allows virtually anything, so one can’t use it to make predictions. The anthropic landscape idea is something more specific, it’s that one can make statistical predictions based on the idea that we must be at a “typical” point of the anthropically allowed region of the landscape. The proton decay argument shows that we’re not, and this is wrong. People pushing this I suppose can argue that they still haven’t worked out exactly what all the states in the Landscape are, and until this is done, one can’t be sure of what will happen. But all the evidence is that there’s no reason for protons to be so stable.
So, oversimplified: landscape not even wrong, anthropic landscape wrong.
The situation is more complicated than just the true statement that “string theory makes no falsifiable statements”. “string theory” is not a well-defined single thing. Many versions of string theory do make falsifiable predictions that are wrong, generically string theories predict several completely wrong things. In order to evade these predictions, people have come up with these very complicated constructions designed to evade falsification.
Regarding Kachru’s demotion of the Anthropic Principle to “if You Wish”, this may be a nod to the cyclic model of Steinhardt and Turok, which of course uses string- and brane-theoretic ideas but is emphatically anti-anthropic (as is clear from their paper “The Cyclic Model Simplified”).
Peter: “1. How do you encourage people to try something new, different than what other people are doing, given that it is most likely to fail? Can one provide incentives so that young people do not feel that they are probably committing professional suicide when they try and do something new and ambitious?”
Well, my opinion is that you should NOT encourage people to do
things that are most likely doomed to fail with little chance for something to show for their efforts. If they do take high risk projects, there is no way to avoid the high chance of a serious damage to their career, the way they are judged by others, and most importantly their self-judgement. There are no riskless risks.
There is one thing you can do. It is to have a culture were high risk ideas are examined, and read, and people think about them and comment on them, and mainly criticize them. In this aspect, when it comes to the string theory debate the people on the string theory side are overall much better.
Christine said:
“I think that the high energy community should attempt to reach a consensus on the status of string theory. ”
I don’t believe that’s possible right now. Physicists don’t like to abandon a theory until they have a new theory to work on (one must publish, even if it is junk) and it is unlikely that a new theory would be accepted quickly. There are (at least 10 fundamental issues on which quantum theory and general relativity are incompatible, even if our choices are choosing from column q or from column r, there are 2^10 =1024 possible choices (it is possible that neither is correct).
Peter,
You like to claim that string theory ‘doesn’t work’. Do you have proof of this statement beyond arguments against the landscape? If the difficulty of connecting with experiment is your sole criteria, then I would counter that this is not a problem with string theory, but a problem of a lack of experimental data at high energies. ANY theory of quantum gravity will have the same problems. Hopefully, within the next year this situation will begin to change as LHC begins to produce data. The smart money is on TeV scale supersymmetry which, while not proving string theory, is strong evidence in it’s favor. Precision experiments that follow should allow us to determine the exact mechanism by which SUSY is broken, information which will help the string theorist. You should keep in mind that what we call string theories are really just perturbative limits of M-theory, which is largely unknown. We need experimental data to get beyond perturbation theory.
PS: I look forward to seeing you eat crow within the next two years.
Thomas Love wrote:
Physicists don’t like to abandon a theory until they have a new theory to work on
That is certainly *not* what I have suggested. Please read my comment again.
Christine
E. wrote:
If the difficulty of connecting with experiment is your sole criteria (…)
Hm. I think it’s more than in time for Peter Woit to write a FAQ about his main arguments.
Christine
Christine,
Difficulty connecting with experiment is the ONLY possible argument against string theory. String theory is the ONLY framework which allows one to combine quantum mechanics, gauge theory, and gravity in a consistent way. If Peter has the ability to refute this statement, then I’d like to see a paper by him on the arXiv which is also submitted to a refereed journal. He can pontificate all he wants, but this is not scientific.
E., you’re missing the point even if all alternatives like LQG with its prion particle model really are dismissable; the connection to experiment is the ONLY possible criterion of science. String theory connects only to speculations; alternatives have less speculation in them, and fewer degrees of freedom. They’re more factual, which is science. Eg, see Feynman video explaining
“It doesn’t make any difference how beautiful your guess is…”
– http://www.youtube.com/watch?v=ozF5Cwbt6RY
Anon,
Again, the problem is not with string theory, but the fact that the energy scales involved are so large that experiments are difficult if not impossible. String theory can make contact with experiment, however it is difficult at this stage to make predictions since we are working with approximations to M-theory. At present, we can only show that it’s POSSIBLE for string theory to describe our world, and then try to work backwards. Yours and Peter’s arguments would essentially argue against the entire enterprise of quantum gravity, not just string theory, on the basis that it’s difficult to make experimental predictions. Any other theory you want to bring up will have the same problem. However, there is only one theory which is mathematically consistent with the potential to do the job, and that is string theory.
Gina,
Woit wrote:
So it is not that he is “encouraging people to do things that are most likely doomed to fail with little chance for something to show for their efforts”. It has to do with the nature of the frontier of knowledge that high energy physics represents today in the search for a quantum gravity theory or the unification of fundamental interactions. It has to do with acknowledging the difficulties involved. So it is to encourage people to work in a difficult subject, yes, but with the expectation that ideas might turn out (more frequently than desired) to be wrong, so one has to be extremely cautious and willing to accept failure as part of such an endeavor. Such eventualities should not be seen as a failure in their scientific careers, but part of it. But yes, the system as structured today is not ready to identify such eventualities as part of the effort, nor is open to encourage new ideas. In consequence (at least, in part), the system ends up to be also insensitive to some undesired distortions.
Christine
“Again, the problem is not with string theory, but the fact that the energy scales involved are so large that experiments are difficult if not impossible. …” – E.
That is a pathetic defense and it is a fault of string theory. A good theory should not build upon unobservables that can’t be checked. This is the whole trouble: string provides solutions for non-existent, imaginary problems on scales that can never be onserved, and in the process requires more uncheckable speculation.
E. wrote:
I’d like to see a paper by him on the arXiv which is also submitted to a refereed journal.
You are not alone in such a desire (but it should not necessarily be a paper by Peter Woit). For a long time I am willing to see a detailed technical argumentation in a refereed journal on the status of string theory, critically assessed. I would expect to see such a paper written even by a string theorist. In any scientific field, it is natural for the researcher to assess the pros and cons, the open problems and discoveries, of their current investigations.
Christine
E. Says:
“String theory is the ONLY framework which allows one to combine quantum mechanics, gauge theory, and gravity in a consistent way. ”
Can you prove that?
Anon,
It isn’t string theory’s fault that nature has placed the unification scale at 10^{16} GeV. Perhaps those ancient Greeks theorizing about the existence of atoms were pathetic as well, since they couldn’t possibly perform experiments to test this idea.
Dear Thomas Love,
This statement was proved in 1984 by Green and Schwarz.
I think I’ve made the arguments I want to make about what the problems with string theory are clearly and in detail in many places. For one version I recommend
http://www.math.columbia.edu/~woit/testable.pdf
Maybe I should write up this sort of thing as a formal paper to put on the arXiv, but I’d rather spend my time on other things. I simply don’t believe that doing so would have the slightest effect on the views of string partisans like E., who have a long list of unshakable ideological beliefs that just don’t correspond to reality (like the belief that the 1984 Green-Schwarz anomaly cancellation proves that “String theory is the ONLY framework which allows one to combine quantum mechanics, gauge theory, and gravity in a consistent way. ”) For the less partisan, there are now plenty of places people can read what I and other string theory critics have to say, see how string theorists respond, and make up their own minds. A few years ago only one side of this argument was readily publicly available, that has changed a lot.
Some string theorists do still seem to believe that the LHC will see supersymmetry, with a pattern of supersymmetry breaking that will correspond to a specific class of string backgrounds, that will then used to make real predictions. From talking to many string theorists, my impression is that the “smart money” no longer has much faith this is going to happen and would not be willing to bet on it. What I’m seeing are people well aware that this hope is looking more and more unlikely to work out, so they are hedging their bets, to make sure that they won’t be eating crow a few years from now.
E. wrote:
This statement was proved in 1984 by Green and Schwarz.
About this paper, here is an interesting comment from one of the authors:
This week’s citation classic: the Consistency of Superstring Theory.
Green writes:
“It isn’t string theory’s fault that nature has placed the unification scale at 10^{16} GeV. Perhaps those ancient Greeks theorizing about the existence of atoms were pathetic as well, since they couldn’t possibly perform experiments to test this idea.” – E.
1. You don’t know for sure that unification occurs at 10^{16} GeV.
2. ‘Atom’ is Greek for not splittable. All the Greek ideas about the atom turned out completely wrong.
The message that I continually get is that LGQ has failed and String Theory is pursued as the only avenue left, while Peter Woit points out that this isn’t even science, yet nobody sees this as the first sign that quantum gravity and the standard model are in deep trouble, rather, they point back to the other failed solution as the better solution because it’s the only “other” game in town that doesn’t include *as many* unproven or semi-established assumptions.
People keep crying-out for a new Einstein, and how we need “seers”, but their insights must be conditionally attatched to one of the only two games in town, or the consensus will kill Albert with its momentum to hell.
PS: (on anon’s comment) Greek atomism was, from a modern perspective, a largely metaphysical hypothesis, notwithstanding some remarkably insightful comments on familiar observations by the Greeks, made in light of atomism. In the hands of Newton and his successors this metaphysical hypothesis was ultimately extraordinary fruitful, insofar as it inspired powerful ideas that were truly testable against observations.
I’ll take E.’s comment as an admission that the founding assumptions of string theory are essentially metaphysical. That’s fine; metaphysical ideas have had an important place in the development of scientific theories, as have criticisms of undisciplined metaphysical speculation by Mach and others. (Einstein arguably appreciated this creative tension better than anyone else ever has.)
However, by now it has become apparent that the putatively scientific spawn of string metaphysics is an interpretive mess. The appeal to observations that might be made with the LHC is cold comfort, because the interpretation of those observations will be as much a mess as the theoretical ideas employed in the interpretation. A whole generation of researchers have been encouraged to accept this state of affairs as normal, and even as defining a new way to do science. It’s not; instead, it is a sign of a profound crisis, the response to which has been a largely myopic exercise in technically clever model-building that leads nowhere.
Nobody will be eating crow in the next two years. The string theory community should be eating crow now, but collectively they show no inclination to do so. Instead, I expect we’ll see a slow dimunition of interest, and an increasingly restless search for alternative ideas. Edward Witten already seems to have moved on (to Langlands and other purely mathematical topics).
anon. Says:
” ‘Atom’ is Greek for not splittable. All the Greek ideas about the atom turned out completely wrong.”
No, the English borrowing of the word to describe the items in the periodic table was wrong. The atomoi of the greek philosophers are the proton, the electron, the neutrino and their antiparticles.
Peter, I don’s see why the proton longevity falsifies anthropic arguments. If the weak scale is small for anthropic reasons, and if the Standard Model (or something like the SM) is the full physics below the Planck scale, then effective theory arguments imply that the proton decay rate is suppressed by 4 powers of the Planck scale i.e. that the proton has a uselessy long lifetime.
Certainly, anthropic arguments would have been much more convincing if the proton lifetime were just anthropically long.
a,
Sure, but according to the statistical landscape philosophy, I see no reason why the SM (or something like it) should be all there is below the Planck scale. That’s a very special theory: generically string vacua have larger gauge groups, and all sorts of Beyond SM physics. If you claim we are living in some generic, statistically likely such vacuum, it will have much faster proton decay, and anthropic considerations won’t save you.
I think to avoid this argument, you have to come up with some reason that vacua like the SM are statistically favored over others. All that I’ve seen of actual attempts to look at large numbers of vacua don’t show anything like this at all.
Peter,
Are you against string theory or just the landscape? I can assure you that many string theorist do not particularly care for the landscape or anthropic reasoning either.
E.
That paper doesn’t even claim to prove the results you’re ascribing to it. It argues that the SO(32) and E8 x E8 string theories _might_ be consistent, not that the string theories are the only possible such theories. You’re really not helping anyone by making such wild claims.
Dear A.J.,
Green and Schwarz proved that the string theories were quantum mechanically consistent and necessary included gravity, for two choices of gauge group, SO(32) and E8 x E8, as you say. I would agree that if someone came up with an alternative theory that had these properties, it would be important and people would pay attention to it, but certainly this is not the case to date. LQG is interesting, but I don’t think it’s possible to construct gauge theories within its framework.
E.
It’s not a question of whether string theorists “like” the landscape or not. Either pertubative string theory on these sorts of backgrounds makes sense, and you have a theory that is unpredictive, or else it doesn’t, in which case you don’t have a theory. Either way, the idea has failed.
Dear E.,
I’m not very impressed by the argument that string theory must be the only consistent quantum gravity theory because it’s the only theory we’ve found in the last 30 years which might be consistent. Quantum gravity is probably the hardest problem theoretical physicists have ever looked at, so we should probably let a few more centuries pass before putting much faith in arguments of this form.
At the very least, I want to see a compelling argument that Connes’ non-commutative geometry theories aren’t low energy approximations to a consistent theory of quantum gravity.
Dear Peter,
I disagree with you that the idea is failed. We simply do not have the complete theory in our hands, only pieces. At present, it really is the only theory that has the potential to explain everything. That isn’t to say that people shouldn’t work on alternatives, as Schwarz and others did in the 1970’s when string theory was decidely out of favor. Perhaps one of those alternatives will be shown to have the same special properties of string theory, but until that day string theory will hold the most interest. It’s much more likely that additional progress will be made in uncovering nonperturbative aspects of string theory that will lead to unique predictions.
Dear A.J.,
If there is another alternative, that would be great. I don’t argue against other approaches, I only point out that at present string theory is the only contender.
Dear E.,
That’s the trouble with words, I guess. When you wrote
many of us didn’t realize that you were only referring to frameworks that we know of. Anyways, if what you’re saying isn’t really different from the standard explanation of string theory’s current state, then we don’t need to continue this conversation.
Best,
Peter,
You seem to be really losing it. You can’t claim that string/M-theory is ‘Not Even Wrong’ and at the same time claim that string/M-theory is ‘Wrong’.
Several people already have tried to point out to you what the problems are with your line of reasoning, but you failed to listen. I tried as well, but you failed to pay attention. In addition you think that you have something better to do than writing a technical research paper which clearly demonstrates that you have no intention of entering into real technical (or professional) discussions.
You are really like a classic internet troll. Everyone tries to explain to him that what he does is wrong, he doesn’t listen, serious people give up explaining, others, mostly who are new to the internal keep explaining, they give up, yet new people come to whom the phenomenon is new, try to explain, doesn’t work, give up, etc, etc, and the troll remains a troll and always finds innocents who try to talk to him without any progress in anything. No real audience, no real content.
Best,
Tim
E,
“additional progress will be made in uncovering nonperturbative aspects of string theory that will lead to unique predictions.”
People have been repeating this line for more than twenty years now, while everything that has been learned about non-perturbative string theory (branes, M-theory, AdS/CFT…) has led in exactly the opposite direction, to a wider variety of phenomena that don’t look at all like they give the SM in any sort of unique way. As far as I can tell, string theorists have no reason at all for the belief that this is going to change except for pure wishful thinking.
Tim,
As far as I can tell you’re not even bothering to read what I wrote in response to your comment about “Wrong” vs. “Not Even Wrong”, preferring to launch into a personal attack on me, all from the cover of anonymity. And I’m an “internet troll”….?