Another Approach?

No, it’s not my solution to things (you know, when patient, tiring, endless, circular discussion and explaining that it is work in progress does nothing to stop the whining of those who’ve made up their mind in advance…) but it certainly makes me laugh out loud! Enjoy:

arguing with a string theorist by abstruse goose

(Click to go to larger version.)

Taken from Abstruse Goose, which is hilarious!* This follows on nicely from yesterday’s post on Polchinski’s excellent “What is String Theory?” talk… See here.

-cvj

(*Thanks JP!)

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23 Responses to Another Approach?

  1. Nige Cook says:

    Thanks for this! Is the claim in the second row of the cartoon (that string theory is only formulated perturbatively) really a serious objection to the theory? Surely quantum field theory itself is only formulated in a useful way (for making checkable predictions) as a perturbative expansion, e.g. the expansion of a path integral into increasingly higher order terms with correspondingly complex Feynman diagrams having more and more interaction vertices, with more and more ‘loops’ of virtual particles appearing and annihilating and thereby affecting the basic interaction of the diagram

    […snip, snip, snipping out of a long, long bit saying just plain wrong stuff about quantum field theory and string theory that is totally misleading, and largely off the topic of the thread. Sorry. -cvj]

  2. Clifford says:

    Nige,

    Glad you liked the cartoon.

    Cheers!

    -cvj

  3. Nige Cook says:

    […snip, snip, snipping out of a long, long bit saying just plain wrong stuff about quantum field theory and string theory that is totally misleading, and largely off the topic of the thread. Sorry. -cvj]

    Sorry I got it wrong again!

    Nige

  4. Clifford says:

    Nige, I’m sorry to seem harsh, but (as you’ve done several times before) you seem to have a way of saying with the appearance of great authority a number of things about very standard techniques and ideas in physics that are just, I’m sorry to have to say, utterly incorrect. (Standard things about non-perturbative field theory can be looked up in a number of very good texts, by the way.) I can’t just leave them there, as they are misleading to the many people who like to look in on (and sometimes join) these conversations to learn something. The record (in the form of a comment) lasts for a long time, and is searchable. I don’t want my blog to be yet another web source of noise and obfuscation about physics.The alternative is to go through step by step and try to correct everything you say, but you do have the habit of writing extremely long comments with this stuff that -in addition to trashing the flow of the thread- means I can spend a long time correcting these misconceptions that you could have gone away and checked first before putting them up. I can’t do that. hence the snipping. That and the fact that this thread is about a joke, not another opportunity for tedious trading of circular and repetitive arguments about why string theory is or isn’t evil.

    Best,

    -cvj

  5. Nige Cook says:

    Hi Clifford, actually I asked a question, and quoted as evidence http://arxiv.org/abs/hep-th/0510040v2 as it’s online, rather than any of the other QFT textbooks I’m studying. But of course the thread is a joke not to be questioned, and I misbehaved for asking a physics question about it. Sorry again!

  6. Angus Prain says:

    Its true that non-perturbative descriptions of some quantum field theories are available is it not? For example we know a lot about instantons and solitons in field theory which are outside the domain of perturbation theory. We know that the object for which we use the perturbation series in order to gain some insight to is the operator equation of motion. A non-perturbative formulation of, say, scalar qft is given by the Klein Gordon equation with interactions. I think with string theory the gripe by some that there is no non-perturbative formulation is that there is no analogous `Klein Gordon’ equation whose exact solutions we approximate with the usual perturbative string amplitudes.

    Angus Prain

  7. Clifford says:

    Angus, indeed, as you say, there is a lot that has been understood about non-perturbative aspects of field theories (which has little or nothing to do with the existence of pair production as Nige seemed to imply in his long (snipped) comment), using a variety of approaches. Much has been learned about non-perturbative string theories by using roughly similar lines of thought, as well as other techniques. We’re still far from understanding a direct non-perturbative definition of string theory – but *the same is true for field theories!*, and so that is not an objection to the formulation in and of itself. I’ve spoken a deal about this stuff in some of the “news from the front” threads.

    Nige – No need to apologize. (No doubt you will now apologize for apologizing – are you from England, by any chance? πŸ™‚ )

    Best,

    -cvj

  8. Christine says:

    Hi Clifford,

    Indeed, a funny cartoon…

    Yet, seriously, I’m curious about what do you think about the points raised by the guy in the cartoon — indeed these are in a nutshell the main criticisms to string theory.

    For instance, points 2 and 3 in the cartoon seem to be less problematic if one considers string theory a work in progress (a solution to these problems could be eventually found); but what about point 1? Do you think that string theory is falsifiable in principle even with the landscape? Or do you think that the landscape must necessarily “go away” in order that string theory eventually becomes falsifiable?

    Thanks,
    Christine

  9. Clifford says:

    Hi Christine,

    I spent well over two years carefully replying to comments and encouraging discussion of all this on two blogs. I really really really don’t see the point of having these discussions in this form if we are going to forget that we had them and have them all over again (and indeed I think that we did two or three complete cycles of this before)… I can’t assume that blogs have no memory, I’m sorry. There is an archive, and the posts and conversations are searchable. Please look there.

    I’m very happy to discuss new things, new points of view, new results, etc… but I am not going to do make the same points all over again. [ This is especially since the most loudly vocal of the people who raise these issues (I don’t mean you) actually don’t want to really learn anything that might change their already made up positions, and in fact would prefer it that the previous discussions where their points were addressed have been forgotten – their agendas have nothing to do with science. So it all gets tiring and a bit pointless. I’m just trying to get on with doing the science. ]

    So sorry, but I can’t do this. I invested a huge amount of time to help create a record of the points and counterpoints, and it is there for all to see. See the links mentioned in the previous post and links therein.

    Thanks.

    -cvj

  10. Christine says:

    Clifford,

    Ok, I will try to make a picture of your point of view on those (old, but enduring) issues from your archives. I am certain to have missed a lot. Forgive my curiosity. I perfectly understand your position.

    Best,
    Christine

  11. Peter Woit says:

    I urge people curious about whether Clifford and other string theorists have answers to Christine’s questions to take a look at the past discussions on this topic here and elsewhere. I don’t prefer that these discussions be forgotten, quite the opposite.

    Clifford,

    “We’re still far from understanding a direct non-perturbative definition of string theory – but *the same is true for field theories!*”

    That’s completely misleading, you know it and are doing this intentionally. Polchinski began his talk (as he has begun other such talks) by explaining how lattice versions of qft, with renormalization handled a la Wilson, give direct, non-perturbative definitions of qfts, but that nothing like this exists for string theory.

    You’re using your blog not to explain things about science to people but to actively mislead them, because this advances your personal interests. Now I see why you go on the way you do about string theory critics. Guilty conscience, no?

    I also found the cartoon quite funny. Somehow I suspect you’re missing the point most people take away from it….

  12. Clifford says:

    Peter,

    Do keep up. There are so many phenomena in field theories that we know appear non-perturbatively that you don’t see directly from a lattice approach. Phenomena such as strong/weak coupling duality, large N behaviour, and so forth, continually tell us that there are useful ways of rewriting *even field theories* non-perturbatively in ways that we’d never had guessed by starting at the original Lagrangian. This is an indication that field theory is non-perturbatively much richer than we might have suspected some time ago, and formulations that get directly at these sort of phenomena could be useful (if they exist). So much of this richness is invisible in any single non-perturbative formulation available so far.

    Pointing this out is not misleading at all, and certainly not deliberate… That’s rather funny. This is me trying to point out that there are lessons we have learned in several other contexts in physics that may have something to teach us here.

    I’m very amused that you consider my posts on science at this blog to be actively misleading people and advancing my personal interests. Everything I do here is in the spirit of pointing out on-going research activity that might be of interest, honestly explaining what people can and can’t do when I have knowledge enough to comment on that, and largely letting people get on with their research programs because I am not arrogant enough to claim that I can decide what they should and should not be doing. In contrast to your activities, I am not prejudging the outcome of people’s research before they’re done with it, claiming (but amusingly, never showing) that I have results that show what they are doing is wrong even though I don’t work in their field and don’t even really understand it very well, and nor am I making up random things about supposedly nefarious non-physics things they’ve done and spreading that as fact to support my case.

    I think that anyone reading our blogs and seeing the two sets of activities can see where the poison is.

    Best,

    -cvj

  13. Peter Woit says:

    “I think that anyone reading our blogs and seeing the two sets of activities can see where the poison is.”

    Sure, I don’t deny that I’ve tried (with some success, perhaps) to poison dishonest hype about string theory.

    Similarly, anyone reading the two blogs can decide for themselves who is being misleading and who isn’t.

  14. Elliot says:

    Christine,

    I am not a string theorist, or for that matter even a practicing physicist, but let me address the point you raise above. The existence or non-existence of the landscape is not in my opinion the fundamental issue in trying to experimentally verify or disprove a stringy approach to reality. It is the fact that the gap between the energy scale we can accomplish experimentally and that where obvious effects of strings will become manifest is many orders of magnitude. So there are really two choices. 1) look at places like the early universe where the energy levels were much higher for such evidence or 2) look for non-obvious effects at energy scales we can replicate. To me the basic paradigm of string theory and its successors is that the fundamental objects that make up reality are not pointlike but occupy space, if only as 1-dimensional vibrating objects. I view this as just one more step in revising our world view from a classical one to a quantum one and it therefore seems very natural.

    As far as the landscape goes, I believe if string theory is or becomes experimentally accessible, it may lead to constraints on the ways things can be compactified and reduce the space of candidates. I don’t think the idea that there are 10^500 or whatever candidates means that it falls outside the realm of accessiblity, and certainly not falsifiablity.

    I neither believe or nor disbelieve that string theory can provide a complete picture of reality. I also support alternative approaches such as Loop Quantum gravity. I don’t know enough to know otherwise so I think we should hedge our bets.

    Understanding the fundamental underpinnings of reality is a grand quest and I fully support this type of research even if it eventually leads to a dead end. The history of scientific inquiry is that sometimes things that come along on the journey can be as valuable as reaching the final destination.

    Regards,

    e

  15. Tumbledried says:

    Dear Clifford, Peter, and others.

    I do not often post on these discussions, but I do have an active interest in theoretical physics. I believe that the goal to understand the true nature of reality is a noble and worthy quest. So, naturally as an undergraduate I was attracted to mathematics and physics.

    Of course I had heard of String Theory. But the more I learnt of it the more difficult and incomprehensible it appeared to be, and not a terribly natural or elegant approach. And although I was not a totally brilliant student, like several of my contemporaries, I do have a rather distinguished academic record. It seemed to me that the string formalism was not the right approach, and I tend to trust my intuition on such matters.

    So I decided to go my own way. Ultimately, along the way, I was able to justify to myself why a naive interpretation of the atoms of reality as one dimensional strings seems a failed approach. I will explain the rationale briefly now, if Clifford will afford me to ramble a bit on his blog.

    As we all know, the core problem of quantum gravity is to reconcile general relativity (Einstein’s theory of gravity) with quantum mechanics. In general relativity particles are points and follow geodesic paths through a Lorentzian manifold. In quantum mechanics, the analogue to particle is a wave function in a Euclidean space. Hence in quantum gravity we must expect the fundamental objects to trace out blurred geodesics through spacetime. In particular, we roughly expect “tubes” to be traced out, with the probability along the “core” geodesic maximal and, if we were to foliate into hypersurfaces the path, the probability density to decay from the core geodesic exponentially fast.

    Now, if in reality we were to model the fundamental constituents of our dynamics as strings, we usually in a 1+1 model think of them as Riemann surfaces. So it is natural to consider the generalisation to a 3+1 theory which would be a tube, possibly with nontrivial topology along the projection to each foliation (which will be a Riemann surface), traveling through our manifold. But there is a natural contradiction with this picture and our picture of what a good theory of QG should be before, in that the probability measure at the core of such a model is zero, and in fact is only nonzero at a particular radius from the core along a hypersurface.

    This seems to me to be very natural and a good rationale for not taking the most naive and literal interpretation of string theory terribly seriously as a legitimate candidate model of quantum gravity. Although I am sure that Clifford, if he is not going to delete this (rather long) message will be sure to put me in the right where I have erred if I have made a mistake in my rough deductive reasoning.

  16. Will says:

    Dear Clifford,

    I think some people constantly need reminding that scientific debates are fought in blackboards and won by publishing papers. While there are some people who play the same game as propagandist do and try to center their non-arguments around buzzwords they know such as landscape, testability et al. I again challenge these misguided people to write a theory of quantum gravity without whining too much and telling rest of us what to do. Please keep up the good work and I find your blogs very refreshing and positive.

    Best wishes,

    Will

  17. David B says:

    Oh yes Clifford I am with you 100% on your response to the endless circles of whingeing and complete lack of genuine production by some people.

    The cartoon is going up on my door and may influence my future responses to certain areas of the web.

    David Berman

  18. Clifford says:

    Hi:

    Will, David B – Thanks! Yes, it is an important point indeed. Happily, most of us are getting on with the actual scientific research and trying to make progress where we can instead of sitting around pointing fingers. (I must repeat, David, that my putting up the cartoon, which I find funny as a parody, does not (as I said in the preface to it) mean that I endorse that approach to argument, even in situations when the person is not open-minded.)

    Tumbledried: – I think it’s best that you study the approach somewhat before coming to your conclusions. But it is up to you, of course.

    -cvj

  19. Tumbledried says:

    Dear Clifford,

    Many thanks for your response. I must admit that I find it difficult to motivate myself to read up on string theory. My style is to read around an area first, learn the prerequisites etc to get an intuitive feel before jumping in and getting my fingers dirty with the meat of a subject. And sometimes my initial impressions turn me off an area >_<. Of course I do often make mistakes and probably do not learn nearly as much as I could if I were less lazy with such things.

    Best Regards,
    Tumbled

  20. Clifford says:

    [Just for the record, I deleted a comment which was about, and included a (largely irrelevant) quote from, someone who has no right of reply here. -cvj]

  21. codeslinger says:

    [… I deleted … someone who has no right of reply here. -cvj]

    How disgusting.

    An academic who practices censorship is the moral equivalent of a priest who practices pedophilia.

  22. somebody says:

    Where does freedom of opinion end? Does heckling in class fall under freedom of opinion? If not, can we all agree that there are no black and white rules about censoring on blogs?

    A lot of the rubbish that is being said about string theory on the blogs merely helps to confuse people who are trying to get a fair jusgment on the matter. It doesnt make sense to demand that there should be deomcracy between the opinions of Clifford, and that of some guy who has already made up his mind before understanding even the basic facts.

    Incidentaly, one comment about Clifford’s comment on the non-perturbative definitions of string theory and field theory: In field theory, at least we have a Lagrangian. In string theory, the ingredients that go into the path integral are themselves not fully understood. This is the sense in whicch it is important to understand the non-perturbative underpinnings of string theory. Making the path-integral rigorous (through lattice or whatever) is a secondary issue in this sense.

  23. Flossy says:

    Of the panoply of wbetsie I’ve pored over this has the most veracity.