Thursday, August 01, 2013

Is supersymmetry a "speculative idea"?

Matt Strassler wrote a mostly sensible text
A Couple of Rare Events
on the media's reaction to the LHCb and CMS' measurement of the decay rate of the rare process \(B_{(s)}^0\to \mu^+\mu^-\). For the first time, the decay rate was measured to be nonzero and it agrees with the Standard Model within something like a 30% error margin. Matt correctly says that some media sell it as a breathtaking success of the Standard Model that nearly kills all the competitors. And he correctly points out that the media apparently think that the supersymmetry is the only competitor of the Standard Model.
Related: The Huffington Post wrote a story about the 4.5-sigma LHCb anomaly (TRF) pointed out by Descotes-Genon, Matias, Virto
I agree with much of what he says. In reality, there are other theories beyond the Standard Model; the precision with which the rare decay was measured isn't too great; some values of parameters of beyond-the-Standard-Model theories have been excluded while others remain perfectly fine, in contradiction with the main message of the media. Well, I have some understanding for the media's approach: supersymmetry is the #1 well-motivated theory for beyond-the-Standard-Model physics which is why supersymmetry is sometimes sloppily used as a shortcut for the whole set. In fact, the relative likelihood that SUSY is the first new physics that will be discovered is getting larger which means that this approximation of "Beyond the Standard Model physics" by "supersymmetry" is arguably becoming increasingly accurate.

However, there's one detail in Matt's text that I simply can't swallow. He uses the word "speculative" a whopping eight times for supersymmetry and all other ideas for beyond-the-Standard-Model physics. I think that this adjective – something that Matt has clearly adopted as a major part of his idiosyncratic language – is totally inappropriate for these theories. Why?

The adjective "speculative" is being used in many ways and the precise purpose of this word depends on the discipline. However, I believe that "speculative" is an international word so even though I am not a native speaker, I can discuss the fine nuances because the Czech word "spekulativní" is arguably used in the same way.

In physics, a "speculative idea" is one that is sort of cool, from a certain viewpoint, but it is an idea that isn't directly connected with the "standard research" that is going on right now, through the usual combination of experimental and theoretical advances. A "speculative idea" is disconnected in this way either because it is
  • apparently manifestly wrong – the word "speculative" is just a codeword for "wrong" that allows the deluded researcher to be treated on par with the proper researchers although he or she is apparently not
  • very unlikely – it depends on assumptions whose probability seems small and that don't seem to be sufficiently justified by any results that are more or less established
  • too philosophical – the motivation for the idea or the assumptions behind it are philosophical if not ideological in character; they are not empirically scientifical in nature
  • too futuristic – the idea is just not appropriate for research by the bulk of the current researchers because the links between that idea and the industry of doable experiments or calculations are very scarce and the situation may only be expected to change in a distant future.
These four descriptions are sort of related, they're not quite independent, and they don't quite exhaust what we mean by the word "speculative" but I think that they fairly capture the point.

Whatever is your favorite defining point of a "speculative idea", I believe that none of them is legitimate to be used for the beyond-the-Standard-Model theories of particle physics, especially not for supersymmetry.

Supersymmetry in particular – and at least some other BSM models to a lesser extent as well – is surely not "manifestly wrong". In fact, there are good top-down arguments suggesting that supersymmetry is, on the contrary, "manifestly right", a mathematically necessary part of any consistent theory of quantum gravity that at least remotely resembles the real world.

One shouldn't assume that supersymmetry has been established as a key part of the description of the collisions at the LHC because it hasn't been established. But its irrelevance hasn't been established, either. Even for a "theoretical agnostic" – I mean someone who doesn't give a damn about theoretical arguments at all – it is right to be neutral about the validity of supersymmetry. There clearly exist supersymmetric scenarios that are compatible with all the observed LHC phenomena. And there also exist non-supersymmetric low-energy effective theories (but not necessarily complete theories including gravity) that are compatible with all the LHC data so far.

An impartial "theoretical agnostic" should assign comparable Bayesian prior probabilities to the "supersymmetric models of Nature" and to the "non-supersymmetric models of Nature". Doing something entirely different – e.g. describing one class as the "default one" and the other class as a "speculative one" – only reveals the bias of the "theoretical agnostic". So this is my recipe of "impartiality" for someone who doesn't assign any weight to too sophisticated theoretical arguments. Matt has violated this rule.

However, I don't really believe that a good physicist should be a "theoretical agnostic". Arbitrarily advanced or abstract arguments that are relevant for finding the right answers to physical questions are things that a good physicist should be interested in and pay attention to. From this viewpoint, Matt's attitude is even more invalid or outdated, if you wish. The top-down research – the only other research aside from the bottom-up research that may introduce any asymmetry between our belief in the supersymmetric and non-supersymmetric theories – actually favors the supersymmetric class. At the scale of quantum gravity, the Planck scale, or at much lower scales, supersymmetry should simply get restored. There don't seem to be any stable, consistent theories including quantum gravity that refuse to respect supersymmetry even at the Planck scale!

So if one introduces an asymmetry and decides to call one class "default" and one class "speculative", it should be done exactly in the opposite way than Matt's way.

Matt's wording is not only wrong but also counterproductive for the research in particle physics because the word "speculative" suggests that the research of these models is something else than the usual empirical science rooted in the empirical data. But the supersymmetric model building in particular is as much standard science that hugely cares about the empirical data as you can get. Matt's adjective "speculative" makes SUSY – and all BSM physics research – sound like a speculative, philosophical, futuristic research or a research of unhinged crackpots. It's none of these things.

I am also dissatisfied with Matt's description of supersymmetry as "one of the speculative ideas to solve the hierarchy problem". The potential to solve or partially solve the hierarchy problem is just one argument among many – and not the most important one in my reading of the situation – in favor of the supersymmetry. The idea that the hierarchy problem is the only justification of SUSY or the only thing to care about and judge new ideas by seems extremely narrow-minded and primitive to me.

Supersymmetry is primarily a symmetry whose restoration seems inevitable at the Planck scale or lower in consistent theories of quantum gravity. It is also a symmetry that produces the most natural dark-matter candidates we know in literature. It is a symmetry that must be assumed to make the minimal particle content compatible with the gauge coupling unification. Yes, it is also the most natural known explanation of the hierarchy problem but also a viable method to achieve other cancellations, even a way to make the C.C. problem less severe quantitatively. SUSY seems also necessary if you think that the number 3/2 shouldn't be missing in the list of integers and half-integers between zero and two. This list is in no way complete.

So the media are conveying a heavily oversimplified and ultimately distorted picture of the reality and Matt Strassler is corrected some of it. But his story still seems excessively oversimplified and distorted to me. Sorry.


  1. Nice post. As someone who pretends to be a "theoretical agnostic" as you say (but really, probably, isn't), I don't think that it should get the bad rap you give it. Yes, attempts to reconcile physics towards the Planck scale leads one to one of several theories, yet people get weirdly religious about their particular choice (as suggested by the word "agnostic"). Let's be honest, you get weird about string theory sometimes too. I'm not saying I think you're wrong, but as a young physicist it seems more important to build bridges than to defend them. It would be surprising to me if there wasn't the need for a radical change in the way we look at some part of physics in my lifetime. So it seems to make sense to me to err on the side of keeping things open rather than closed. And so on and so forth.

    Anyways, I really just wrote here to point out that you list four things and then say "These three descriptions...". Just thought you should know.

  2. Gosh, I have only read the title but it already reminds me of an issue I had with Matt Strassler when reading an article about gamma ray bursts a few months ago on his site.

    He explained two mechanisms how they can be produced, one (for lower energy gamma rays) is well established among astrophysicists, and the second one is still some kind of an open issue, but there exist very well grounded, well motivated theoretical ideas about how the second mechanism (producing the higher energy gamma rays if I remember correctly) could work.

    Now, gamma ray burst is a nice "down to earth" enough astrophysics topic that even a large majority of sourballs (or sourpusses') accepts. But I had almost to stop reading Matt Strassler's article, because in every sentence (sometimes even twice or thrice!) he called the ideas how high energy gamma rays are produced speculative, as speculation, etc; to me it seemed every second sentence contained such an adjective. Boy did this high repetition frequency of calling reasnable physics considerations speculative disgust and annoy me ...!!!

    So I could not help it but I had to write a comment over there, asking Matt Strassler, why it is not enough to call the explanations for the second mechanism "speculative" only once (if at all!) when he mentions it the first time, why well motivated from a physics point of view theoretical ideas have to be called speculative (which is in my opinion quite insulting to people working on these things), instead of calling them just theoretical ideas.

    Scientist should not give an inch to sourballish claims, often issued by laypeople who have no clue, to call all theoretical work or considerations speculative and what else :-(0) !!!

    Now, I'm gonna see what this TRF article says :-)

    Sorry for the potentially inappropriate spam :-P

  3. Exactly, Dilaton. I noticed some very different yet equally inappropriate contexts in which the adjective was used, too.

  4. kashyap vasavadaAug 1, 2013, 9:06:00 PM

    Could you write a (simple!!!) review blog on super symmetry emphasizing how it could be broken and possible range of masses of super partners which can be seen in 2015 LHC runs and ILC?
    Kashyap Vasavada

  5. I am not sure if this is relevant here but I have noticed that in the less mathematical sciences where the word "conjecture" is not much used, it is often replaced by the the word "speculate". You can find many papers in which the author says "we speculate that..." in roughly the same meaning as when I write "we conjecture that...". As an illustration, here is a random example found on Google (there are lots of them): ""We speculate that SOCS3 could be a new target for vaccines to improve the protection against Tuberculosis," says Martin Rottenberg". So it could be that the intended meaning of "speculative" would be "conjectural", which I don't think has any of the negative implications that you list.

  6. Matt in his agony to be “politically” correct and not to take a stand about any issue which is not 100% resolved, is often exaggerating with his wording (at least in his blog); trying to use a very cautious, neutral
    language he often sounds like Wikipedia. It’s very annoying in my opinion and more importantly, misguiding for the uninformed reader. This is a typical example…

  7. The requirement that new theories have first of all to correctly reproduce well established experimental and theoretical knowledge such as the standard model as an effective QFT or GR in certain limits and must not contradict any known physics laws and facts, puts quite a lid on how wide things can be kept open.

    People loudly crying for revolutions in our understanding of physics often forget, dont know, or dismiss this simple aspect of the scientific method.

    If I remember this correctly, Lumo has once written a whole article about why science does NOT advance by a series of radical revolutions that overthrow all the scientific knowledge the society has accumulated again and again...

  8. Dear Lumo,

    from my natural speech comprehension, the "speculative" issue has an even more negative connotation than you mention. How I naturally understant this term, what you say is just the most good will interpretation as I explained to Matt Strassler over there in a comment:

    "Thanks for this again very nice, interesting, article :-)

    but there is again one issue which bugs me, that I have already noted in another generally very nice article about the physics and production mechanisms of gamma ray bursts. Maybe it is just because I am not a native English speaker, but to me it seems adjectives or nouns like "speculative" or "speculation" have a very strong negative connotation. From my natural, maybe wrong or too naive speech comprehension, saying that somtheing is "speculative", a "speculation", etc is in its most negative interpretation quivalent to saying that this something is bullshit, rubbish, nonsense, crap, a crazy idea without any reasonably justified motivation backing it up, etc and in the most good willing interpretation it has the meaning of an idle philosophical idea or metaphysics, which is not legitimate physics either. Calling something speculative or a speculation gives the impression that the something is completely worthless.

    So my question here is: is it really needed that theoretical concepts such as supersymmetry or not yet settled down explanatory ideas how high energy gamma ray bursts are produced for example (neither of them is just worthless unmotivated nonsense!), is consequently paired with the adjective "speculative" or with the noun "speculation" repeatedly each time it is mentioned, sometimes even more than once in the same sentence?
    Why can alternatively, theoretical ideas and concepts which are not (yet?) directly experimentally confirmed and/or settled down not just be called "theoretical ideas" and that's it? I think many regular readers of this site have a good enough idea about which theoretical ideas and concepts are settled down and which issues are still some kind of open. And even for people who have not (yet) a large physics knowledge of their own, such that they can not judge this issue completely on their own, it would be enough to call a theoretical concept or idea "speculative" or a "speculation" at most once in the same article, for example when it is mentioned first. Surely none of the readers here are that forgetful, that they have to be reminded with such a high repetition frequency of the fact that something is not yet settled down ...

    Maybe it is just me, but reading texts with such a high repetition frequency of "speculative" adjectives and nouns, used to characterize by many physicists considered not completely nonsensical things, strikes me quite odd ..."

    And Lumo,

    have you seen the answer he gave to a commenter called Bob Anderson asking him for his opinion about a certain paper?

    There I have notet not for the first time (!) that Matt Strassler rightly so admires the often good excelent work of experimental physicists, but he often reveals that he thinks not much of theoretical physicists. Maybe because those are the people who do the speculative things :-D?

    I even remember him saying in a comment quite some time ago now, that you (or your judgement? Opinion about something?, darn I forgot the exact wording) can not be trusted, because you are a string theorist (I am not joking!). That was so breath takingly off the mark, that it was almost funny and I could not avoid having to chuckle about it ;-P

  9. andrew oh-willekeAug 2, 2013, 2:12:00 AM

    The ordinary meaning of the word "speculative" in my line of work (law) where it is used quite a bit in a fairly ordinary sense is that something could be true but that there is a dearth of evidence affirmatively showing that it is true. If you say you were hurt but don't provide medical records or other evidence, you damages are speculative. But, if you then return with X-rays and a diagnosis, they cease to be speculative.

    A word with more neutral connotations but approximately the same meaning in this context would be "hypothesis". The word "conjecture" is also a synonym of speculation, which has a very similar negative connotation outside STEM fields, but has a positive connotation within STEM fields since many STEM conjectures have later been proven to be true.

    In the sense that Matt is using the word, I think that he is saying that while SUSY is possible and theoretically makes sense as a concept, that there is no clear experimental evidence showing that what it adds to the empirically established Standard Model actually exists (of course, SUSY incorporates the vast share of the basic insights of the Standard Model like how quantum particle wave functions act if a particle has a particular set of properties). If could exist given the evidence we have, so it is merely speculative rather than being definitely wrong, or probably wrong (i.e. experimentally or theoretically disfavored). But, without some solid empirical BSM data point consistent with SUSY but not the Standard Model it is only a credible but unproven hypothesis.

  10. kashyap vasavadaAug 2, 2013, 3:09:00 AM

    I have a question. When broken SU(3) was discovered, one of the results was a mass difference equality for baryons which gave a big boost to the broken SU(3) . Is there any such formula for broken super symmetry between partners or between hadrons and SS partners? Thanks.

  11. The root of the word speculate means "to see." Compare, e.g., spectacles.

    The modern sense means "seen with the mind" as opposed to those things seen by direct observation. Despite occasional uses of the word in a disparaging sense, I think the more original sense "seen with the mind" fits supersymmetry very well.

  12. You can't use the language and reasoning of Sanskrit which began to emerge 1500 before Christ to answer subtle questions about the 21st century theoretical physics. Everyone seems to agree that the word "speculation" is used to mean something else than a "conjecture", see e.g.

    You may close your eyes and pretend that there's no difference but that won't make it true.

  13. Dear Peter, the word "agnostic" may sound attractive to you (probably for some ideological reasons of yours) but in the context where I used it, it is equivalent to "ignorant or overlooking many segments of scientific evidence" and it should definitely be getting a bad rap because it's a sign of bad science.

    Just to be sure, there are contexts - e.g. experimenters working on a particular experimental procedure - when almost all the other evidence is ignored because it's needed for the true independence of the experiment. However, such an experimental procedure is far from having formative influence on all the scientific conclusions. Scientific conclusions may only be obtained by judging all the available evidence. For some questions, one experiment may be more than enough; for others, it's not.

    If you use the word "religious" for getting serious about many kinds of evidence, including those routinely overlooked by others, or - if I am much more general - if you use the word "religious" for the "passion for the truth", then yes, science is a religion in this sense. Your call for a revolution is just an artifact of your being ignorant about the scientific facts and the logical interconnections between them and I would recommend you to reduce your arrogant proclamations by some orders of magnitude.

  14. No, I couldn't. It's not a simple business. And the SUSY breaking schemes and various extensions of the SUSY models etc. are numerous, are backed by various justifications, and there's no objective way to compare them and give them weight.

  15. Dear lucretius, I don't think that there is any difference between the meaning of the words "speculate" and "conjecture" between physics and "less mathematical sciences". Instead, the resolution of your "paradox" is simpler and sort of funnier: the less mathematical sciences are simply not sufficiently refined to formulate solid (too many) enough hypotheses that would be called "hypotheses" by the physicists, so they can only do what physicists would also call "speculations", and they call it speculations, too. Your vaccine example is a very good one. They are just making a guess, there's pretty much just one type of procedure to decide whether the guess is right, and the procedure doesn't seem to be linked to research that was already done.

    But it's exactly an aspect of superioty of physics that it can formulate hypotheses=conjectures that are much more than speculations because they have many consequences and implications for/from the research that has already been done.

  16. Dear Dilaton, a wise comment. I agree that "bullshit" is the frequent meaning of the word "speculation" and I ultimately put this interpretation at the very top of my list, too. But it's not the only one. After all, even credible top scientists are allowed to "speculate" at some points and it's accepted that they may be right. But when it's a speculation, it always means that if many people began to do "research" on it, it would only lead to complete chaos. This is clearly not the case of SUSY and many other topics in science.

    I think that Matt is a very good theorist who has done almost no speculations but lots of credible conjectures, models, and analyses of the models, so I am confident that his reasons to use this bizarre language are something else than a dismissal of the whole theoretical physics community. However, I surely do share your perception that Matt thinks that physics (or science) may progress "just" by experiments and the role for theorists is non-existent or secretary-like. In the past, even very recent past, he has done some fine theoretical work that shows that this assumption is invalid but it's conceivable that he participated in that work only because someone else pushed him to do so and if one cares how Matt really feels, he probably does feel that a theorist should only be a secretary to the experimenter who does some straightforward work and shouldn't think much. That's surely my reading of all the messages of the unusual wording and the messages in between the lines.

  17. Dear Andrew, I have already written the same answer to lucretius but here we go again: there isn't any tangible difference between the law and STEM. You don't use "hypotheses" too often because the methodology of law simply doesn't allow one to create "hypotheses" that are more than speculations, at least in most cases. And the hypotheses in STEM often turned up to be right for reasons that are not just random: it's because the detailed quantitative content of STEM disciplines, especially physics, allows one to make more-than-just-guesses that have very good reasons to be true. The reason why you're unfamiliar with such a thing in the context of the law is that the scientific methodology of the law is too unrefined to do such things; and/or that the thinkers about the law are less capable to do such things than the physicists.

  18. Dear Kashyap, there's no such known implication of SUSY that would be both universal and accurate enough. In the case of SU(3), one may only derive such things because one implicitly assumes that the breaking only occurs by some rather specific mechanisms. The flavor symmetry is violated by mass terms etc. Certain identities have to hold. SUSY has to be broken by a whole new sector outside the MSSM spectrum and this breaking is communicated to the Standard Model in ways that aren't unique, either. This non-uniqueness of the breaking mechanism makes it impossible to deduce similar general laws.

  19. Just have a question with the wording of this sentence:

    "And he correctly points out that the media apparently think that the supersymmetry is the only competitor of the Standard Model."

    Does any reputable writer think supersymmetry COMPETES with the Standard Model? The Standard Model is necessarily a limiting case of supersymmetry, right? (Educate me if I'm making a semantic or fundamental error, here.)

  20. BTW it would be also good to clarify the usage of the term "exotic". I'm not sure in which exact context this term is used and whether it has a negative meaning.

  21. I completely agree with this, but it seems to me that there are two somewhat different issues involved here.

    The first is, whether Matt Strassler is trying to disparage SUSY - and I don’t think you are suggesting that. Now that I have read this text I see that he uses “speculative” not just for SUSY but for any theory or theoretical idea that is not regarded as fully established, e.g. he writes

    “you typically can’t rule out any one speculative idea with a single measurement”.

    but just a few lines above that and referring to exactly the same thing he writes:

    “if every measurement with a precision of about 30% that agreed with a theoretical prediction had been hailed as a triumph for the theory, there would be a lot of embarrassed scientists around… a lot of predictions have failed only after much better precision was available”.

    So it seems to me pretty clear that he uses “speculative idea” and “theoretical prediction” as essentially synonymous.

    The second issue is what effect this sort of frequent use of “speculative” will have on his readers. Well, I think that depends who reads this blog. On physicists, mathematicians, and people working in all theoretical sciences it will have no effect at all (except that some will see it as a public display of pedantic “impartiality” in the style of Wikipedia - as pointed out by Giotis). It certainly may have a misleading effect on people from outside these fields (if such people read this blog). But a lof of such of people regard even the word “theory” with the same disrespect as “speculation” - which is why we frequently hear the phrase “it’s only a theory”. But it’s hard to imagine how you convey the true situation to them in a short space and without resorting to the sort of propagandist language that AGW proponents habitually use.

  22. Dear Rob, I've never claimed that the writers who write such things are "reputable". But I did write that they're almost everywhere in the mainstream media.

    The Standard Model as a limit of a supersymmetric theory is an OK idea but you must understand that SUSY has many parameters so its parameter is multidimensional and one can take many possible limits. Only some of them reduce to the Standard Model. In other limits, more generic ones, one still gets predictions that qualitatively differ from the Standard Model.

    For example, one may say that it's "generic" for the minimal supersymmetric models to predict several Higgses that are comparably heavy to the known one - clearly a different result than the SM result. But there are also limits in which all the Higgses but one are infinitely heavy, and so on.

  23. Dear Giotis, well, "exotic" means "unusual", not a part of the business-as-usual life etc. Only racists think that e.g. exotic beauties inevitably carry negative connotations.

    In string theory, "exotic" is used in various technical well-defined ways. Exotic branes are those that weren't originally listed by Polchinski etc. They carry various unusual charges, monodromies, and so on.

    It's clear that some words have a well-defined technical meaning. But the word "speculative" is a general word whose meaning is taken from the colloquial ones. You won't find an equation defining a speculative idea.

  24. The first is, whether Matt Strassler is trying to disparage SUSY - and I don’t think you are suggesting that. Now that I have read this text I see that he uses “speculative” not just for SUSY but for any theory or theoretical idea that is not regarded as fully established, e.g. he writes

    Right but a refined interpretation could be that he is trying to disparage all phenomenologists' research of new physics. Or something else. I don't understand what his real goal is but I think that I do understand what is the impact of his wording.

  25. As for the first part - see my edit. As for the second - of course you are right but this time you are being excessively pedantic. Obviously I know that idea and prediction are not synonymous (everybody knows that) - I was suggesting that Stassler was using "theoretical" and "speculative" as synonymous. Actually, as I wrote in my in my "Edit", I noticed that the "theoretical" referred to the Standard Model and "speculative" to SUSY, which I would consider unjustified, but I am not convinced that Stassler is in any way anti-string since he describes himself as someone working on sting theory (I have not checked his paper though).

  26. Dear lucretius, sorry for my being pedantic. If it were the only reason, then we are on the same frequency.

    Matt must have decided to use the word "speculative" instead of "theoretical" for some reason. I believe this is no coincidental slip of tongue but a part of a plan he has been thinking about for quite some time and that is meant to achieve a goal that isn't quite known to us although some people may have proposed sensible suggestions where the wind blows from.

  27. ... the strange thing is, that my comments over there do not get deleted but Matt Strassler or anybody else does not reply to them either.

    I mean, what should they reply when I bluntly ask why theoretical ideas and concepts are not just called by their proper names characterizing accurately what they are, namely theoretical ideas and concepts ...?

    If Matt Strassler would want to reply, he would either have to agree with my point or admit, that he calles theoretical ideas and concepts speculative and speculations on purpose, based on some hidden underlying agenda we do not (yet) fully understand ... ;-)

  28. Now that I have learned (by looking at his publications) that he is (or seems to be) primarily a string theorist, the only hypothesis that comes to my mind is that he is trying to establish a reputation for impartiality and non-partisanship among his wide circle of general readers, but making it quite visible that he is not favouring the theories he has been associated with himself. In fact, he might even be bending a little to far in the opposite direction. I think that he thinks that in this way he builds up his credibility among the general public and even those suspicious of string theory and SUSY, while his reputation in the professional circles is not in danger, since it is based on his research and not his blog.

  29. Yeah I agree that Matt Strassler is capable of and has done very cool theoretical physics, given nice lectures (I have some scripts sitting on my laptop), etc ...

    But to me it seems he no longer likes much of these things and people working on them today...

    ... if he has ever liked it at all ...?

    His attitude concerning BSM physics is a big mistery to me. Sometimes he bashes people who try to ask him about BSM physics in the comments, and then again when people ask questions it is him who starts to mention string theory for example in the replying comment... :-/
    (Shrugging my shoulders)

    I really dont understand him, but generally his physics articles are often quite a nice reading (if the speculative terminology is not too overabundent) and he most of the time patiently and nicely answers questions in the coments

  30. Exactly,

    I got the impression too that he does not want to be associated with string theory and things he has worked on in the view of the pulic ..

    But then he should probably delete the comment in his "About me" page that says that he has written papers about string theory and just say theoretical physics or something like this ...

    Maybe I should tell him this ... ;-P?

  31. Using the “speculative” terminology in this excessive and highly
    repetitive way for any theoretical ideas and concepts as they appear in
    different subfields of physics, conveys to the public and/or laypeople
    audience the wrong and somehow misleading impression that physicists,
    who are interested in and working on rather theoretical aspects of these
    physics topics (including those who try to suggest phenomenological
    predictions), are people who do nothing else than pulling wild ideas out
    of their sleeve or out of thin air without any scientific reasonable
    motivation or justification.

    People working on and intereste in the rather theoretical part of
    physics are not some lazy good-for-nothing who peacefully lay in the
    shadow of a tree the whole day and idly make up some crazy ideas …

    This is how I see it and what I said to Matt Strassler over there too ...

  32. Actually, I think you should wait for his reply first. It's only around 7 a.m. where (presumably) he is located. I expect he will reply to your posts and it should be interesting.

  33. Dear Dilaton, he's fair enough to allow your comments. The word "speculative" is obviously no typo that he would just "fix". It's a choice that he has made after some thinking, for some reasons he must find important, and it's probably counterproductive to try to convince Matt to "fix this typo".

  34. Dear Lucretius, he has written some very influential papers and I would agree that at least 12 of his 15 most important papers may be called string theory papers. At the same moment, it seems spectacularly clear that he has drawn a thick line behind all this activity and he would even reject to be called a string theorist. None of the circumstances leading to this "conversion" are comprehensible to me.

    Of course, I've met Matt many times - at Harvard, in Seattle, and we could have met at Rutgers as well. But I feel that there are two Matts and the Matt from the blog is someone very different from the Matt as seen through his most well-known papers.

  35. Well, Dilaton, he can't change the fact that most of his most famous papers are de facto string theory papers, can he? Or should he? You can't rewrite the history. Whatever the reasons behind his "negative conversion" are,, you shouldn't be asking him to rewrite the history.

  36. Exactly, and the idea that the HEP theorists are just pulling wild ideas out of their sleeves is something that not only the laymen but even folks like some condensed matter PhD students, or people in other adjacent disciplines, may adopt. In some sense, I feel that this is even more dangerous than if a complete layman reaches some misleading conclusion.

  37. Yeah, from time to time there are even questions on Physics SE from (physics) students who ask if thinking about or persuing theoretical or fundamental physics is still worthwhile etc ...

    This is not a good sign at all ... :-/

  38. Dear Lumo,

    of course I agree ;-)

    My comment was just a (probably bad) joke intended to highlight the weirdness of Matt Strassler trying to "disassociate" these string theory papers from his account ...

    Of course he can rightly so not change the history.

  39. Dear Lubos, what about GR not being the final classical theory of gravity? Does this invalidate the need for SUSY? Thanks

  40. Invalidation of GR would surely be a more radical modification than "just" invalidation of SUSY.

  41. Well I know him from the Klebanov-Strassler duality cascade and as far I understand Klebanov handled mostly the stringy part while Strassler the field side. So this makes him I suppose the dual of a String theorist :-)

  42. Thanks Lubos,

    I am a layman studying String theory on my own and I have to admit that when I see the term "exotic' in a text or a paper, what comes automatically in my mind is that this must be something weird not worth of pursuing it further...

  43. That's strange, I am attracted to similar objects - probably for the very same reason why you're repelled.

  44. Well, as I predicted, he replied. Clearly all of us (Including myself) who thought he was using "speculative" without careful deliberation were wrong. Now he explains carefully why he did it. Actually, he also explained his view of string theory in an earlier reply to Harry Bostock.

    "For these reasons, particle physicists can and should continue to learn the basic mathematics and results of supersymmetry; I would never advise a student not to learn it, even if never shows up in an experiment. Same with extra dimensions and string theory; these are powerful tools of great value, even if they have nothing to do with nature directly."

    He now makes clear that he thinks that:
    " string theory, supersymmetry, and extra dimensions are more likely to be false than true. And that’s what the word “speculative” is meant to imply."

    But he still thinks it is a "an interesting scientific theory".

    Well, I think this is just the right place for me to stop. I am certainly very curious about to know Lubos's reaction ;-)

  45. Well, at least the students won't suffer but the opinion that string theory is more likely to be wrong than right is batship crazy.

  46. In addition to exotic, the term esoteric probably needs clarification
    too, since for example Manishearth, a (non physicist!) Physics SE
    moderator callels all BSM physics esoteric.

    I felt first very insulted, but then he explained to me that esoteric just means that only a small number of experts/specialists can really understand these topics ...

    What do you Lumo and other people think about the esoteric terminology in the context of BSM or fundamental physics?

  47. Yep, here is Matt Strassler's reply to my second comment:

    "This was a decision made on my part after considerable reflection.

    I’d rather have my readers understand that string theory,
    supersymmetry, and extra dimensions are more likely to be false than
    true. And that’s what the word “speculative” is meant to imply.

    This is to counter the impression given by many proponents of these
    ideas that they are more likely to be true than false… or even that
    they’re obviously true and it’s just a matter of little experimental

    “String theory tells us the world has ten or eleven dimensions…”

    It’s poisonous quotations like that which need an antidote. String
    theory remains a fascinating, brilliant, elegant, exciting
    ***speculation***. What makes it better than *idle* speculation?
    First, it has a complete, well-defined set of mathematical equations
    that make it meaningful. That’s what makes it a scientific theory. And
    those mathematical equations address key questions of how quantum
    mechanics and gravity, as well as other particles and forces of nature,
    could coexist in one framework. That’s what makes it an interesting
    scientific theory.

    It’s my job to convey the distinction between idle speculation and a
    real scientific speculation. I’d use the word “theory” but that word
    has so many meanings, and is so toxic and confused in modern parlance,
    that it is useless."

  48. I guess spacetime-torsion could not be eliminated yet as a theoretical possibility by any experiments. So a simple last question: does ST contains in any low energy limit the Einstein-Cartan theory? Thanks

  49. What a bizarre answer, I didn’t expect it. I thought he was
    just trying to keep a balance. What does it mean that String theory and SUSY
    are more likely to be wrong than right. How can you quantify that and assign probabilities?
    Such terms are not even applicable for a scientific theory of this status. I
    really don’t understand him now and I’m deeply disappointed by Matt.

  50. As far as I know, Einstein-Cartan theory in its original form is impossible according to string theory.

    String theory generally contains fields like the H-field 3-form. But if you analyze things by the stringy maths, you soon or later understand that the Einstein-Cartan theory isn't really natural and its building blocks aren't irreducible yet they are combined in a way that assumes the irreducibility.

  51. Matt Strassler also replied to my question. I am posting here only his reply, which is quite informative (and more interesting than my question, which is why I am not posting it here):

    You are right to criticize my glib language here; I wasn’t being careful. I do mean mainly that history is never kind to theoretical ideas; when there are competing ideas, it usually turns out that all of them are wrong, or one of them (at best) is right. Sometimes it turns out more than one is right in a surprising combination. But it is a bad idea to get into the habit of thinking that because theorists have thought of a good idea, it is likely to apply to nature.

    String theory is still the best bet among theories that humans have invented **so far**. I’m not as certain as some of my colleagues that we’ve thought of all the possibilities. And string theory has so many manifestations that I’m not sure that the one that’s relevant in our universe has been imagined yet. But who cares what I think? Nature is nature… so don’t pay any special attention to me.

    I have no qualms about working on string theory when it answers questions of interest to me. I view it as a tool. I think, as a mathematician, you should view it the same way.

    There are many examples of “false” physical theories that provide enormous physical and mathematical insight. The most famous examples are the maximally-supersymmetric and near-maximally-supersymmetric quantum field theories (so-called N=4 and N=2 supersymmetry.) These theories cannot have the chiral symmetries of the quarks and leptons in nature, so we know they are “wrong” (in the sense of not being able to describe nature.) Another example is the theory that contains only gluons and no quarks (often called “Yang-Mills theory”) and its N=1 supersymmetric version; we know these theories aren’t “true”. And yet, we have gained enormous insights into all sorts of physical processes and calculational techniques using these “false” theories. The same is true for their contributions to math: at least one Fields medal and many other awards have been won and will be won soon using the N=4 and N=2 theories. So I think you are suffering from belief in the same myth that many others suffer from: it is simply not the case, in history or in the present, that the most elegant and symmetric theories are the ones that we find in nature.

  52. Yep, I am very disappointed too, which lead to my next comment over there, which I better not reproduce here because it containes too many words that should not be mentioned here on TRF ;-)

    It might be slightly exagerated too, but I felt really irritated by this strange answer ...:-/

  53. Well at least he admits it’s just silly to say that String theory or SUSY is more likely to be wrong than right. It really was an unfortunate,
    void statement for a theorist of his status.

    He says:

    “And string theory has so many manifestations that I’m not sure that the one that’s relevant in our universe has been imagined yet.”

    I don’t have a clue of what he is trying to convey here. Our Universe is just a solution (a vacuum) of String theory equations. Why is that so hard to imagine?

    Then he says:

    “I have no qualms about working on string theory when it answers questions of interest to me. I view it as a tool. I think, as a mathematician, you should view it the same way.”

    All that nonsense repeated once again. You often hear it here and there: String theory is a “tool” or String theory is a “framework”. No String theory is a physical theory which unifies all fundamental interactions. Period.

  54. Well said Dilaton.

    In his answer to you he mentions:

    “Meanwhile, if there is
    *SOME* backlash against what some of the string theorists have done, encouraging
    all those young people to strive to be the *mythical* Einstein (who spent all
    his time thinking deep theoretical thoughts, of course), and the backlash
    drives young people to focus more on proposing and explaining experiments (like
    the *real* Einstein), that would be a good thing for science. I make no
    apologies if I accomplish this.”

    Again the usual silly accusations to String theorists i.e. that they are detached from reality (even Gross implied that in Strings 2013). This is just a naïve simplification and an empty rhetoric. There is no dichotomy between the *mythical* and the *real* Einstein. Einstein was doing both and string theorists are doing both. There is a whole discipline called String
    phenomenology; Matt is aware of that of course. On the other hand by pushing
    the theoretical boundaries and trying to understand the deep structure underlying
    the theory is of fundamental importance. It’s not a mathematical game; each
    time a theoretical issue is resolved we understand better and better the nature
    of *reality*.

    I really don’t understand
    these people sometimes. At the end I feel they are just defending their carrier paths and the choices they have made. Nothing more…

  55. Yeah, there seem to be fewer and fewer physicists doing fundamental physics who truely love the subject, such as Lumo and Nima for example ... :-/

    As Matt Strassler allows string theory at most (if anything) to take the role of a mathematical tool or clever trick, like a transformation to a more convenient coordinate system where the solution to a physics problem can be found easier, he naturally is annoyed most about string phenomenologists (people doing formal theory as he calls it, he tolerates to a certain degree, as long as there are not too many of them). You should have seen how he quite some time ago now (last year?) spit and spat on Gordy Kane and colleagues and their work when asked about it in the comments, calling there work something like completely unfounded nonsense and even quite insulting Gordy Kane personally by saying he is dishonest and such things. So I hold myself back then and refrained from asking him what he thinks about Cumrun Vafa's CKM-matrix calculation etc ... :-P :-D ;-)

    Thinking about the quote from his answer you repeated, I can not help getting the impression Matt Strassler would not mind if string theory and everything related to it would just disappear, if for example all young physicists are scared away from such research. Currently, they are scared away not because anything speaks against it from a scientific point of view but because of the public well organized witch hunts, polemifications, and demonization of fundamental physics by well known and unfortunatelly successful activists, and the scornfulness with which people who are working on or interested in such topics are treated publicly at an increasing number of places (at least in the internet and maybe in the real world too).

    So I am not quite sure how much I should feel sorry for my follow up comment to Matt Strassler's answer, how (in)appropriate it really is in fact ... :-/?

  56. Speculation = Contemplation that means thoughtful observation . Speculative ideas carry the risk to be not true . It doesn't mean it's not mainstream or wrong. Supersymmetry (which I think is most possibly true ) which is not confirmed yet might not be true . It's based on mathematical reasoning about the world but it's not an inevitable consequence as far as I know .

  57. That is as we have learned by now not how Matt Strassler uses the speculative terminology. He explicitely said on his site that he applies it to say that suppersymmetry is most probably wrong for example ...:-/

  58. Dilaton if you want my opinion using the term “esoteric” to describe BSM research is
    just idiotic. BSM physics is just good old physics; it is what physicists are doing and always have done i.e. expand the boundaries of our
    knowledge and acquire a deeper understanding of Nature.

  59. Is one of those theories basis for a GUT or TOE? If that's the case, would it likely done already?

  60. I think people are bothered by Strassler’s use of the word “speculative” because he misuses it. In common usage there is a newness involved when one says that some idea is speculative, i.e. not much thought has gone into it. When an idea has been carefully examined one gets more quantitative. Something may have a probability between 0.1 and 0.2 for instance and, within that uncertainty band lies ignorance

  61. Exactly, Gene, I completely forgot about this aspect of the word "speculative": it is also something that hasn't been investigated in detail.

  62. For Wikipedia editors:

    Maybe you want to edit

    this wikipedia article about spacetime, where string theory is called speculative in the summary right above the table of content:

    Maybe one should scrutinized generally a bit the articles about fundamental physics in Wikipedia ...?

  63. Good lord, this is silly. Since when is this a blog on linguistics? Speculative means "based in conjecture, rather than knowledge." It's easy enough to open a dictionary, and no... I don't agree that the meaning of the word depends upon the field you are discussing.

    So, yes, SUSY is indeed speculative, unless you have some data to share that says otherwise that you would like to share. Now, whether it was informative or relevant for Matt to point this out a number of times: that is debatable.

  64. No, this is not about language, it's primarily about the content. SUSY is clearly not speculative according to your definition, either, because it is based on knowledge.

  65. Look at the latest comments of Matt Strassler here

    he clearly and explicitely says he usese the "speculative terminology" for things he considers to be more probably wrong than right.

    So it is clearly not just a stylistic language issue, on the contrary!

    Applying this terminology not only to BSM fundamental physics, but generally to theoretical ideas, concepts, and considerations even in fields like astrophysics, clearly reveals his dismissive attitude concerning the theoretical part of physics.
    Specifically his latest comments in this thread my well have a the effect of strongly discourage people who read his site and take him serious from beeing further interested in any BSM fundamental physics, because he states that all of this is most probably wrong.

    These comments of Matt Strassler may have a much stronger negative impact on BSM research than anything the many nonexpert dimwits and trolls could do and say, becaue Matt Strassler is himself a very capable theoretical physicist.

    I am still disheartend and disappointed by these comments ... :-/

  66. What happened to adjectives? I mean if you insist to use the term ‘speculative’ and you don’t have bad intentions you could always accompany it by the corresponding adjective e.g. well motivated, well established, well founded etc. On the other hand if ‘speculation’ means ‘conjecture’ then why not use this term instead? You could just say then e.g. ‘well founded conjecture’.

    Note that these positive adjectives don’t fit nicely with the term ‘speculation’. We don’t say for example ‘well established speculation’. On the other hand this term matches nicely with negative adjectives; for example we often say when we want to criticize an unmotivated idea ‘this is pure
    speculation’. This is exactly because the term ‘speculation’ has a negative meaning.

    But I don’t have to say more, just look Matt’s response to Dilaton and you will understand why he has chosen to use this specific term.

  67. Once again, I have to disagree. According to the dictionary definition, a conjecture is "an unproven mathematical or scientific theorem." If you have proof of SUSY, I certainly hope you will share it with us.

    Since when are theorists afraid of conjecture?

  68. Exactly,

    Matt Strassler does not pair it with a positive adjective, because there simply is nothing positive in the way he applies the "speculative" terminology ... :-/

  69. I did't disagree with - and, in fact, I explicitly endorsed - the statement that the relevance of supersymmetry for an XY class of phenomena is a conjecture. It is.

    I disagreed with the statement - a different statement - that supersymmetry is *based* on a conjecture. It's not and therefore it is not a speculation.

  70. No, I disagree with where you are drawing the line. All viable theories are informed by knowledge (with the exception of crackpot stuff or theories that ignore previous data.) So, if that is the bar, no reasonable theories for BSM physics are speculative. However, a key motivation for SUSY is an aesthetic ideal, naturalness, and a conjecture that our universe cannot be fine-tuned at some completely arbitrary level. That makes it speculative for me. A counter-example would be finding the Higgs or another clear source of EWSB. That was based entirely on knowledge and thus was not speculative.

    OK, that's enough distraction. Cheers from Snowmass.

  71. So, if that is the bar, no reasonable theories for BSM physics are speculative.


  72. In the context of the results being discussed, the issue wasn't SUSY in general but rather at currently accessible scales. So, I don't feel I am being impolite in defending Matt's original statement with my respectful disagreement, especially given his broad audience that is really interested in things we may learn in our lifetimes and won't appreciate the distinction.

    As for your statement about Snowmass, thanks for raising your middle finger at experimenters and data. I guess we can stop paying attention to you then.

  73. BSM theories are indeed viable theories informed by knowledge so indeed no reasonable theories for BSM physics are speculative.

    The reason you neverthelss agree with reasonable BSM theories calling speculative is, as I guess that you dont understand them and there on knowledge based motivation well enough.

    Calling all reasoable BSM physics theories speculative looks therefore quite disrespectful towards people working on these things and their work too.

    This has nothing to to with raising any fingers at anybody or anything ... ;-)

  74. I would like to suggest a compromise (at the risk of having everyone turn against me).
    First, Lubos’s intuition was definitely right in this case. He argued from the start that Matt’s repeated usage of “speculative” was deliberate and intended to show himself an “agnostic” on the question of the truth of SUSY. In fact Matt confirmed this himself and even went as far as to say that the point he wanted to make was that SUSY was “more likely wrong than right” - although he went back on this claim after I pointed out that it did not really make sense. Matt also provided a strong argument in favour of string theory (and by implications SUSY) as a tool for getting insight into physics and mathematics. For me this is more important than the question of “truth” in this case.

    In fact, it is clearly characteristic of Matt’s general attitude on his blog. He tries very hard to give the impression that he is in the “mainstream” and not a partisan of anything in particular. At the same time to wants to retain his scientific integrity and avoid endorsing any demagogic claims. But in some cases this leads him to a seeming contradiction. One example is his latest post on AGW, where he says sensible things and then ends up with meaningless conclusion (“it is time to stop experimenting with our planet” - whatever that means).

    However, I feel Lubos goes too far in seemingly attempting to set rules about the usage of the English language at least as far as the usage of the word speculate is concerned. Nobody can hope to succeed in this in the case of English - people will continue to use it in various ways as they have always done. It is not true that the word speculate is used in science exclusively or even mostly with in a negative sense and mainly in reation to “crackpot theoreies”, not even by string theorists. I have just made a check of a number of books and papers: including those by Witten, Weinberg, Polchinski, and many others. It is generally used as something weaker than “conjecture” - most often in cases where there are more than one reasonable hypotheses. Here is a typical example from “String Theory and M-Theory” by K. Becker. M.Becker and J.Schwarz:

    Witten has speculated that the existence of such a three-dimensional theory might indicate the existence of a theory in four dimensions with no supersymmetry that upon circle compactification develops an N = 1 supersymmetry in three dimensions. This is one of many speculations that have been considered in attempts to explain why the observed cosmological constant is so tiny.

  75. Lucretius,

    It’s one thing to use the term ‘speculation’ for a hypothesis within the context of a theory (like in Becker-Becker book) and another thing to use it for a theory as a whole, and I’m talking here about well-established theories like String theory (and consequently SUSY as a symmetry of nature) and not some unprocessed idea.

  76. You are right, but I was only disagreeing with the idea that the word "speculate" generally carries a pejorative meaning. In fact, people seem to use it in two ways. When they are referring to ideas they do not like one can usually detect a pejorative intent. But, as often happens, when they refer to their own idea it is meant to suggest modesty or non-commitment and the meaning is not pejorative.

  77. This is not a blog on linguistics but careless use of a word leads to misunderstandings. The precise meaning of any word is context dependent, among other things, and it is silly to use a dictionary when discussing the fine nuances of meaning.
    I think Mark Twain said it best when he said that the difference between almost the right word and the right word is the difference between the lightening bug and the lightening.
    Either Matt Strassler is a rather poor writer or he simply put too little effort into careful crafting of his prose.

  78. Exactly, Lubos. That captures the difference very well. To be credible a hypothesis does not have to have more than an even chance of being right; it just has to be not unreasonable. A speculative hypothesis means that more contemplation is needed.

  79. No, it's not just the above motivations you cite (namely naturalness, aesthetics etc). It's impossible to motivate what I'm going to say without equations, but in short, whenever one tries to unify gravity and quantum mechanics (Prof. Witten often explains SUSY to be 'fermionic co-ordinates' of spacetime) (by which I mean all known string theory vacua and any attempt at the high energy description of gravity), to put it an oversimplified fashion, SUSY seems to be inevitable, at a conceptual level. The motivations and reasons that you mention are those that are generally thrown around in pop-sci books and blogs, but in detailed technical analysis somehow it's inevitable that supersymmetry appears. If SUSY is manifested at colliders at accessible energies (by which I mean superpartners are found) great for us, but if it's not, then nothing much changes, because the equations simply require it. The fact that it's broken (and how) is possibly the deepest puzzles around in theoretical physics. To stop my rambling, I want to just state that there're much more deeper conceptual reasons not to call SUSY a mere 'speculation' just because some phenomenological manifestations aren't found at low energies.