Various Links

  • The 2016 LHC proton-proton run is now over, with delivered (41.07 CMS/38.4 ATLAS) and recorded (37.82 CMS/35.5 ATLAS) luminosities (in inverse fb) far above the goal for this year of 25. Together with last year’s data, the experiments now have 41.63 (CMS) and 39.4 (ATLAS) inverse fb recorded at 13 TeV, close to the LHC design energy of 14 TeV. It is likely that preliminary results will be reported at an “end-of-year jamboree” in mid-December, with more to come at the winter conferences.

    I’d guess that these new results will see improved bounds on SUSY particles, and that David Gross and Lubos Motl will have to pay off their long-standing bets that the LHC would find SUSY (Gross’s bet with Ken Lane is here, it says 50 inverse fb of LHC data, sum of CMS and ATLAS now about 80). Unfortunately, I’m afraid that losing these bets won’t affect their devotion to SUSY.

  • Paul Steinhardt gave a colloquium at Fermilab last month with the title Simply Wrong vs. Simple. In it he explained “why the big bang inflationary picture fails as a scientific theory” (it doesn’t work as promised, is not self-consistent and not falsifiable). This is a complicated topic, but Steinhardt is an expert and one of the originators of the theory, so if you want to understand the problems of some common arguments for inflation, watching this talk is highly recommended. Steinhardt’s talk was part of a Fermilab workshop, Simplicity II.
  • On the multiverse front, Sabine Hossenfelder’s Mom has Sabine to set her straight. For professional physicists, instead of getting set straight there’s the usual Templeton funding for the opposite, in this case a workshop on Fine-tuning, the Multiverse and Life.
  • Paul Ginsparg discusses various issues having to do with the arXiv here and here, with an emphasis on the question of how to decide which preprints to reject (they have my sympathy on the difficulties involved). Ginsparg notes that they decided not to have comments/discussion of papers there, but to have “trackbacks” to discussions hosted elsewhere. Still no indication of why trackbacks here are banned.
  • Theoretical physicist Walter Greiner passed away a couple weeks ago. He was the author of a series of textbooks, one of which in particular, Field Quantization, I found very helpful when I was trying to figure out some details for the book I was writing.

Update: I just noticed that Witten’s Commemorative Lecture for the Kyoto Prize is available here. It’s a very interesting account by him of his career and point of view.

Update: In case you think fine-tuning is a central question in physics, besides the Templeton-funded workshop in Sydney, you can consult the website of a Templeton-funded program, or buy this book by a Templeton-funded author. There’s also a talk by Aron Wall, given to a Rutgers University apologetics club. Wall’s conclusion is that either God or the Multiverse did it, and he comes down on the side of God (because of the Resurrection of Jesus business).

Update: Also on the Templeton front, they are funding a new $7.2 million Black Hole Initiative, which advertises itself by

The BHI will be the first center worldwide to focus on the study of black holes, and as such it offers a unique naming opportunity for potential donors.

Templeton is paying for the first three years of this. To get some idea of the scale of this project, the yearly grant is roughly half the size of the NSF grant to each to the two largest US centers in pure math and in theoretical physics (MSRI and the KITP).

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16 Responses to Various Links

  1. Anonymous says:

    Interesting quote: “Each problem here involved applying physics ideas to a problem that traditionally would have been viewed
    as a math problem, not a physics problem. These were all problems that I would not have seriously considered
    working on until String Theory broadened our horizons concerning the relations between mathematics and physics”

    In particular because he talks about his paper on QFT and the Jones polynomial.

  2. Bee says:

    The field quantization textbook was mostly written by Joachim Reinhardt. Who, sadly, enough passed away a week before Greiner. And thanks for the link. My mom appreciates it 😉

  3. curious says:

    Together with last year’s data, the experiments now have 41.63 (CMS) and 39.4 (ATLAS) inverse fb recorded at 13 TeV, close to the LHC design energy of 14 TeV. It is likely that preliminary results will be reported at an “end-of-year jamboree” in mid-December, with more to come at the winter conferences.
    ^

    if LHC sees no evidence of SUSY after recording and analyzing that many inverse fb recorded at 13 TeV, and possibly reported by dec- 2016, what are the probability LHC will ever see SUSY over its entire lifetime i.e after it collects 3000 inverse fb? with 5-sigma being discovery?

  4. Peter Woit says:

    curious,
    There’s no well-defined answer to that, since there is no sensible notion of probability distribution for different susy parameters. One can say thought that by the standard “naturalness” arguments, SUSY was supposed to show up at the (masses 100-200 GeV), and definitely early on at the full energy LHC (masses around 1 TeV). That’s what David Gross was willing to bet money on. I think we’ll soon see gluino mass bounds above 2 TeV. Much later on the LHC may be able to get bounds up to say 3 TeV. I’m pretty sure though that Gross would turn down an offer of a “double or nothing” bet that superpartners will show up later on at the LHC.

  5. Peter Woit says:

    Anonymous,
    One thing about the Witten piece is that he is rather defensive about string theory (very explicitly in the last part), not surprising given how things have not worked out. The comment you quote is interesting in that he credits string theory more with causing a change in point of view and change in culture that led to some of his great work. It’s certainly accurate that string theory and the way Witten pursued it with a lot of mathematical firepower changed a lot how physicists looked at mathematics (I think there has however been a backlash more recently, as many physicists blame mathematics for the failures of the research program).

    But, ignoring that, I think his comments about the relation of math and physics in his work (as well as the role of string theory) are really fascinating. One thing that has always struck me about him is that, even when he was revolutionizing some fields of mathematics, it always seemed that he was leery of getting too much involved with the mathematics, wanted to stay grounded in physics. My own reaction to some of his great work was quite different, as it led me to want to learn more about the mathematical context in order to better understand how mathematics and physics were interacting.

    On the one hand I think he has always been aware that his strong suit is that he can do things mathematicians can’t, by exploiting what physicists know. It’s also true that he is driven ultimately by a deep motivation to solve certain problems in physics, which is quite different than the motivations of mathematicians. He mentions explicitly something usually not mentioned, that from the beginning of his career, a deep motivation has been that of trying to solve QCD, and because of this, trying to better understand non-perturbative QFT. In particular striking to me was his comment:
    “I am not sure that there is any such thing as being an expert on how quantum systems behave for strong coupling, and in any event certainly I myself never have become such an expert. I have learned quite a bit while always feeling like a beginner.”

  6. milkshaken says:

    I really enjoyed Paul Steinhardt lecture – accessible to nontechnical audience (like me) – and I admire his plain-speaking courage (given that he is one of the founders of inflationary cosmology).

  7. Miki Weiss says:

    Thanks for the reference to Aron Wall lecture. He shows the logical absurds in the Anthropical principle and the String Landscape with the shortest and most elegant reasoning.
    Why the Anthropic Principle is absurd? – see slide 38.
    Why the String Landscape is absurd? – see slide 41.
    But he still gives the Inflation Multiverse the benefit of doubt, if inflation is proven by experiment to be correct….

  8. jonW says:

    I thought Steinhardt’s talk was excellent, too, and I find it a very commonsensical approach to really examine the degrees of freedom available to inflationary theories and what this means for their notability as predictions. Just for the sake of balance, though, does anyone know of a paper or lecture (pitched at a similar level) that gives as strong a rebuttal as possible to Steinhardt’s criticisms? I know those criticisms aren’t exactly new.

  9. Ben says:

    I think many people are aware of Steinhardt’s criticisms, which mostly boil down to the fact that inflation doesn’t really solve problems so much as kick them down the road a bit. Instead of flatness/horizon problems, you now have questions about initial conditions or bubble nucleation in eternal inflation, etc.
     
    But to the extent that developed alternatives even exist, they don’t seem much better. Ekpyrotic/bounce scenarios really just shift the question to “how do you propagate density perturbations through the bounce”. And since the methods used to do so have to violate something or other (usually the NEC), there’s skepticism that a clever theorist will eventually figure out how to get any prediction you want out of that model, too.
     
    So it’s not so much that people rebut Steinhardt or don’t believe him, it’s just that nobody knows what else to do. I will say that I think that many observational people will start eyeing inflation with a lot more skepticism if B-modes don’t start showing up soon (i.e. if limits get down below 10^-3).

  10. Scott Church says:

    Peter,

    I know Aron Wall, and I can tell you that between God and the multiverse he does not consider God to be the better answer to fine tuning because of “the Resurrection of Jesus business.” What he does believe is that given the current state of cosmology and QFT, demonstrated physics + God is a more robust and less ad-hoc explanation than that offered by the inflation/string theory multiverse + Materialism… a conclusion I agree with. His reasons for thinking so can be found in more detail at his blog. He mentioned the resurrection in that talk only to to point out that because he already has other reasons to believe in God including that one, the former is a viable option for him whether science progresses further on the matter or not. As such, he can objectively weigh both alternatives because he has no prior commitment to either outcome, whereas, materialists who wish to claim scientific authority are stuck with the latter whether they like it or not , and have little choice but to go to whatever lengths are necessary to make it work… up to, and including dispensing with the need for testable predictions in science. For more on all this, see Aron’s post about that talk and the resulting comment thread, pro and con.

    For better or worse, physics has brought us to a place where we’re knocking on the door of ultimate origins where the delineations between it and metaphysics are starting to blur, and it’s becoming increasingly important to understand how the two relate to each other. To date many, if not most scientists have been reluctant to do so and now the chickens are coming home to roost. Thirty years ago it was commonplace to see philosophers and theologians addressing scientific topics with little or no training in the relevant fields (case in point, creationism). Today we’re starting to see the reverse as well… physicists practicing metaphysics while professing themselves to be above doing so, and as such doing so unconsciously, and therefore badly. Aron, who is well-trained in both, is one of the more notable exceptions to that disturbing trend.

  11. Peter Woit says:

    Scott Church,
    I wasn’t pretending to do justice to Aron Wall’s views with that off-hand remark, thanks for giving a more detailed explanation of his views . My views on all this are tediously simple: “God did it” and “the Multiverse did it” are equally vacuous non-explanations and those who want to debate them are doing something I’m not interested in and that I don’t think qualifies as science under even a generous interpretation of the term. And I think most physicists agree.

  12. Lars says:

    “God did the multiverse”

    God did the multiverse
    And string theory too
    Cuz after the universe
    He’d nothing to do

  13. Goose Gossage says:

    Thanks for the link to Fermilab, Peter. Paul Steinhardt’s talk was exciting. The headline: there are now two types of bounces that have been worked out — one quantum and one classical. One involves a quantum violation of the null energy condition, and the other a stable classical violation. That’s clearly a very big deal. For each, one can now compute what effect there is on the perturbations. Odds are there is no effect on the large scales that cosmologists measure — too early to say what that the prediction will be until a careful computation is done. But Steinhardt said there WILL be a definite prediction, unlike inflation which has turned out to be dependent on extremely unlikely initial conditions (as proven by Planck) and the multiverse, which produces every darn thing imaginable. It’s no secret that Steinhardt’s argument has long been that inflation makes no predictions (because you always wind up with a multiverse, which means it predicts….everything). At Fermilab, he was saying it’s not right to compare a fundamentally unpredictive idea (inflation) with a scientific idea (a bounce) that WILL be able to make a prediction. I think that was the real point of his lecture.

  14. Avi Loeb somehow forgot to mention his John Templeton Foundation funding in his recent bit of ‘Nature’ tripe. My how far the mighty have fallen.

    http://www.nature.com/news/good-data-are-not-enough-1.20906

    I doubt my comment to this would pass moderation at Nature anymore.

  15. Shantanu says:

    Peter, sorry for the OT link, but one more
    article by Avi Loeb for astrophysicists on why non-mainstream ideas
    should be encouraged
    http://www.nature.com/news/good-data-are-not-enough-1.20906

  16. Pingback: String theory might be about to finally be killed off | Not Even Wrong

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