Quick Links

Taking off tomorrow for a long weekend, internet access may be spotty. Here are some things that may be of interest:

HEPAP is meeting today and tomorrow, the presentations given at the meeting are available here.  JoAnne Hewett is there and has a posting on Cosmic Variance.
The Seed article with various physicist’s views about what to expect at the LHC that was discussed here earlier is now available online.

There’s an article about Jim Simons in Newsday (via Angry Physics).

Maybe a cosmologist can comment on the significance of this, but over at CosmoCoffee there’s a discussion of a new paper reanalyzing the latest WMAP data and coming up with a scalar spectral index ns= .969 +/- .016. This is now 2.0 sigma away from 1, instead of the 2.7 sigma of the earlier analysis. This deviation from 1 was widely sold as evidence for inflation (since the simplest inflationary models give values slightly less than one), the fact that it is now only a 2 sigma effect seems to make this case a bit weaker.

The Institut Henri Poincare in Paris will be having a three-month-long program on Groupoids and Stacks in Physics and Geometry. The web-siter there contains a good associated overview of the subject.

Bruno Kahn has an excellent expository article on motives.

Over at the Edge web-site Lawrence Krauss has a piece called The Energy of Empty Space That Isn’t Zero. It’s partly about the cosmological constant, and discusses a workshop on Confronting Gravity that he organized back in March, which brought many prominent theorists together at a Caribbean resort to discuss physics, travel in a submarine, and hang out at the “private island retreat” of the funder of the event, science philanthropist Jeffrey Epstein.

Krauss has many provocative things to say about the current state of theoretical physics, including perhaps the most concise and vivid description I’ve read in a while:

It’s been very frustrating for particle physicists, and some people might say it’s led to sensory deprivation, which has resulted in hallucination otherwise known as string theory.

He also has a somewhat longer skeptical take on extra dimensions, together with an attempt at positive spin:

Many of the papers in particle physics over the last five to seven years have been involved with the idea of extra dimensions of one sort or another. And while it’s a fascinating idea, but I have to say, it’s looking to me like it’s not yet leading anywhere. The experimental evidence against it is combining with what I see as a theoretical diffusion — a breaking off into lots of parts. That’s happened with string theory. I can see it happening with extra-dimensional arguments. We’re seeing that the developments from this idea which has captured the imaginations of many physicists, hasn’t been compelling.

Right now it’s clear that what we really need is some good new ideas. Fundamental physics is really at kind of a crossroads. The observations have just told us that the universe is crazy, but hasn’t told us what direction the universe is crazy in. The theories have been incredibly complex and elaborate, but haven’t yet made any compelling inroads. That can either be viewed as depressing or exciting. For young physicists it’s exciting in the sense that it means that the field is ripe for something new.

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21 Responses to Quick Links

  1. For young physicists it’s exciting in the sense that it means that the field is ripe for something new.

    This should be exciting not just for young physicists, but for everyone. When David Gross talks about not understanding what is space-time and Roger Penrose wants to change quantum mechanics, that’s a sign of something big coming.

  2. Peter Woit says:

    Eugene,

    I’d like to be that optimistic, but I seem to remember both Gross talking about getting rid of space-time and Penrose wanting to change QM at least 15 years ago. Krauss is right that the time is ripe for people to give up on things that haven’t worked and try something new. Will they do it though?

  3. rof says:

    Right now it’s clear that what we really need is some good new ideas.

    The anthropic principle, extra dimensions and parallel worlds. These are the new ideas you will hear about, again and again and again. They are the exciting new ideas that each generation of daydreaming physicists echo again and again. They aren’t even new ideas.

    And anyway, if somebody announced what the correct new idea was today, they’d be dismissed as a crackpot. A good old fashioned no-nonsense attitude has thoroughly infused the physics community. As a result, they are dismissive. If there is a lesson to be learned from string theory, it should be that it takes careful investigation to distinguish between nonsense and complex but correct ideas. But that lesson will not be learned. People display dismissiveness because the immature are impressed by dismissiveness and consider it worthy of imitation.

    Each individual physicist will insist that he is perfectly reasonable. All you have to do to convince him that your new idea is worthwhile is immediately produce a full theory of quantum gravity and have it endorsed by some celebrity physicist (even though that celebrity physicist will make the same demand of you before listening to your idea). Otherwise you’re a crackpot.

    Physicists need to face the facts: As a community, they’re too immature to be able to provide an environment where new ideas can be communicated without ridicule. Too much narcissism and arrogance. Children.

  4. Peter,

    I was not suggesting that new big ideas will come from Gross or Penrose. Most likely, not from them, in my opinion. I was just hinting that the current state of disarray, when frustrated people are willing to give up the most secret things, is a prelude to some radical change. I just smell it in the air. You are right that in order to move forward we should not be afraid of new crazy ideas. The question is: how “crazy” is good enough?

  5. Anon says:

    The reduction of the significance that the spectral slope of the primordial perturbations is less than one does not have a strong effect on the possibility of inflation. The spectral slope may be used to distinguish between various potentials for the inflaton. But the current experimental constraints are not that discriminating. There are a couple of s that were favored pre-wmap but now give a bad fit to the data. The PLANCK satellite will dramatically improve this situation. So will better polarization measurements by ground and balloon based experiments. Ultimately, a polarization satellite will probably be needed to really be conclusive.

  6. Krotos says:

    For young physicists it’s exciting in the sense that it means that the field is ripe for something new.

    My take on this as a youngish physicist is that I’d like to believe it, but the fundamental problem that has led particle physics (and, increasingly, cosmology) to the current situation is the inability to satisfactorily test these theories experimentally. And I don’t see that changing any time soon. Even the LHC will be orders of magnitude below the energies necessary to really probe the physics behind, say, dark energy or inflation. The best we’ll be able to do with forseeable technology is pretty much what we’re doing now, i.e., indirect observations and inferences from astrophysical measurements. That’s good and valuable, but generally it doesn’t provide the precision necessary to do more than favor one large class of models over another large class.

    Yes, one can certainly hold out hope that some 21st century Einstein will come up with a rigorous, revolutionary new theory that unifies gravity and quantum mechanics and explicitly predicts the value of the cosmological constant, etc. But historically, that kind of thing has not tended to occur in the absence of data.

  7. Who says:

    Krotos, I beg to differ
    **… not tended to occur in the absence of data…. **
    which suggests there is a lack of observational data.

    On the contrary, one might say that theorists now have TOO MUCH data. More data than they know how to assimilate. If you are a theorist today, you have dark energy (70 percent of universe) and dark matter (another big part). You will soon have results on very high energy gamma photons and cosmic rays from projects such as GLAST (2007) and AUGER (current).
    Dark matter you can see very clearly in galaxy rotation and lensing. Dark energy or its equivalent is seen clearly in accelerating expansion and in the microwave background. These look like major puzzles of just the sort that a theorist could wish for. Imagine if you could make a model of spacetime and matter that would fit all this hugely unexpected data!

    And I mean fit even APPROXIMATELY, to first order. You seem to be asking for higher precision measurements to distinguish between closely similar models, when, as far as I am aware, we don’t even have the beginnings of a model to explain the measurements we already have.

  8. Krotos says:

    You seem to be asking for higher precision measurements to distinguish between closely similar models, when, as far as I am aware, we don’t even have the beginnings of a model to explain the measurements we already have.

    Certainly there’s a lot of “data” in the sense that dark matter and other non-SM phenomena have been indirectly observed and have had approximate limits put on their density fractions by WMAP and other experiments, and of course any unified theory would have to predict these. But my point is that it would, IMO, be extremely hard to construct an underlying particle physics model from which you could “derive,” say, inflation, without knowing, even approximately, what the inflaton mass/potential/etc. even is. And the same goes for dark matter and dark energy. What forseeable astrophysical observations will be able to determine their properties even remotely to the extent that a controlled experiment in a laboratory could? That’s what I meant by saying that there isn’t enough data, and what data there is isn’t precise enough.

    I agree with you that we don’t have even the beginnings of a model that simultaneously predicts these things — I just don’t see how we’re going to get even to that with cosmological measurements alone, let alone to something with the precision of the Standard Model.

  9. Krotos:

    I disagree. How can a theorist be not excited about the current mess in theoretical physics? Even in the absence of new experimental data, there are so many delicious paradoxes within our theories that are just screaming at us begging for resolution. Take for example two completely different ways the time is treated in quantum mechanics and in relativity, and the whole issue about the incompatibility of QM and GR, or the problem of UV divergences. These are deep problems and they require some bold thinking. I wouldn’t complain that theorists have nothing to do until LHC begins to deliver data.

  10. Krotos says:

    Eugene, certainly I agree that these are fascinating problems and deserve a lot more investigation and thinking about fundamental concepts like time and space. But as I said in my response to Who, I just don’t see how we’ll be able to get beyond the theoretical speculation stage (even with LHC data) on them. Theoretical physics in indeed arguably in even a bigger mess now than it was in 1900. But the difference, IMO, is that in 1900 the technology either existed or was on the horizon to experimentally investigate the problems physics was then facing. The data informed and enriched the theory. For the most part, that’s not the case now.

  11. Krotos:

    Yes, in 1900-1920 when there was an ocean of new controversial experimental data, it was much easier to develop theory. Now we don’t have this luxury, and we should draw inspiration form internal theoretical inconsistencies rather than from comparison with experiment. This is much more challenging, no doubt about that. However, I think this is just as exciting now as it was then.

    I think we will start to make progress only after we admit that there is something wrong in our textbooks (about special and general relativity, QM, and/or QFT), even though these theories passed numerous experimental tests. I don’t think we have this courage. I see that from discussions on Peter’s blog: it is next to impossible to convince people to admit mistakes even it the research program that passed zero experimental tests. I am talking about string theory, of course.

  12. Sebastian Thaler says:

    Peter,

    Lubos is now calling you a jellyfish on his blog.

  13. nigel cook says:

    Sebastian,

    As soon as stringers are defeated scientifically (which is as soon as they make any type of claim to be scientists), they have to either retreat quietly, or else start calling people names which they hope will be taken as insults.

    These insults tend to backfire. Anyone can throw that sort of thing around. All it shows is a lack of ability to either succeed with a scientific discussion, or to admit he has no answer, like a responsible adult. His trick in the review of Not Even Wrong, comparing string theory to evolution is extremely misleading.

  14. D R Lunsford says:

    Speaking of quick links,

    This article in Time repeats the fantasy that Mileva Maric was key to the development of relativity, specifically that she “helped [Einstein] with the math of his 1905 paper”. This claim is absurd – the math is Maxwell’s equations and simple algebra, and was common knowledge. In fact Maric failed to gain a teacher’s certificate in 1900 because of low math scores, and left ETH in 1901.

    How did this revisionist falsehood work its way into the public mind? I see this as passive hostility to Einstein himself (despite the usual fawning), and somehow connected with the current devolvement of science into superstition and mysticism.

    See also here:

    http://physicsweb.org/articles/world/17/4/2/1

    -drl

  15. nonblogger says:

    Another quick link then: next september there will be a conference in Cambridge (UK) on the “fundamental structure of space and time” gathering mathematicians and physicists (Connes, ‘t Hooft, Schwarz, Penrose, Douglas, Hawking, Freidel, etc.)
    http://www.newton.cam.ac.uk/programmes/NCG/ncgw02.html

    The aim seems to be to put people from all sorts of backgrounds (strings, LQG, non-commutative geometry,etc.) in the same room. I hope some videos of the talks and panel sessions will be made! (Too bad that the main sponsor seems to be the John Templeton Foundation…)

  16. Hey, I will attend to the meeting pointed by nonblogger. And I should solve the problem of accommodation for at least a couple months, not only the meeting. Any idea, please mail me (al.rivero # gmail.com)

  17. Chris W. says:

    Regarding the above-mentioned conference, note the participants and theme of the planned panel discussion. The Templeton Foundation’s influence seems pretty obvious here.

  18. sunderpeeche says:

    Why don’t you fund your own conference, free of Templeton Foundation influence? Recall the song from 1946 about the foundation of Brookhaven National Lab (~ Cold War + Big Science)

    —x—x—

    – “Take Away Your Billion Dollars,” by Arthur Roberts (1946),

    Up on the lawns of Washington the physicists assemble
    From all the land are men at hand, their wisdom to exchange.
    A great man stands to speak, and with applause the rafters tremble.
    “My friends,” says he, “you all can see that physics now must change.
    “Now in our lab we had our plans, but these we’ll now expand,
    Research right now is useless, we have come to understand.
    We now propose constructing at an ancient Army base,
    The best electro-nuclear machine in any place.
    “Oh – it will cost a billion dollars, ten billion volts ‘twill give,
    It will take five thousand scholars seven years to make it live.
    All the generals approve it, all the money’s now at hand,
    And to help advance our program, teaching students now we’ve banned.
    And as the halls with cheers resound and praises fill the air,
    One single man remain aloof and silent in his chair,
    And when the room is quiet and the crowd has ceased to cheer,
    He rises up and thunders forth an answer loud and clear,
    “It seems that I’m a failure, just a piddling dilettante,
    Within six months a mere ten thousand bucks is all I’ve spent.
    With love and string and sealing wax was physics kept alive,
    Let not the wealth of Midas hide the goal for which we strive.
    Oh — take away your billion dollars, take away your tainted gold,
    You can keep your damn ten billion volts, my soul will not be sold.
    Take away your army gen’rals, their kiss is death I’m sure.
    Ev’rything I build is mine, and ev’ry volt I make is pure.
    Take away your integration, let us learn and let us teach,
    Oh, beware this epidemic Berkelitis I beseech.
    Oh, dammit! Engineering isn’t physics, is that plain?
    Take, oh take, your billion dollars, let’s be physicists again.”

  19. I had not seen the Panel, but bet Connes is able to bypass any reverend.

  20. Chris W. says:

    More from Seed Magazine: A review of Mark Ronan’s Symmetry and the Monster and Avner Ash and Robert Gross’s Fearless Symmetry, by Jordan Ellenberg.

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