Cosmological Frontiers

Last week the Perimeter Institute ran a Workshop on Cosmological Frontiers in Fundamental Physics and someone wrote in to point out to me that the talks are now available on-line. Much of the workshop was about mainstream cosmology, especially the more speculative ideas about inflation and what signals might be found in the CMB.

The particle physics component was heavily weighted towards Landscapeology (talks by Denef, Kachru, Kleban), with a workshop-ending talk entitled “50 Years since the LHC” by Nima Arkani-Hamed. Arkani-Hamed’s talk was supposed to be a prediction of what things would look like 50 years after the LHC, and he ended it with the prediction that “the LHC will put the last nail in the coffin of mono-vac theories” and that “the Landscape will be with us to stay”. Along the way he went over various possibilities for what the LHC might see and their implications for whether the cosmological constant and the weak scale are anthropically determined. He said that he believed the cosmological constant was anthropically determined, and half the time he thought the weak scale was too, the other half of the time he thought it wasn’t. He argued for giving up on coming up with new mechanisms for electroweak symmetry breaking since “working on the (N+2)nd variant on the (N+1)st model of EWSB is not worth it”, saying that instead people should participate in the LHC Olympics and work on the “inverse problem” of figuring out from LHC data the 105 parameters of the MSSM or some other model of beyond standard model physics.

Near the beginning of his talk he gave a graph representing (as a function of time) the average string theorist’s view of the probability that string theory could be used to calculate standard model parameters. This started out near 1 in 1985, dropping to a small number in 1995 after the duality revolution showed that strongly coupled strings didn’t get rid of the wide range of possible backgrounds, and further dropping to “a number close to the fine tuning of the cosmological constant” in 2000 after the advent of the Landscape and the non-zero cosmological constant. The same graph also included a plot for the views of “clueless popularizers and science journalists”, which had only recently started to head down slightly from 1. He claimed that such people are ten years behind the times and that it is “not going to be pretty” when they catch up with the current views of string theorists and realize the theory can’t predict anything.

While at Perimeter, (according to Lubos Motl) Arkani-Hamed was talking to LQGer Laurent Freidel about Doubly-Special-Relativity in three dimensions. It’s going to be a lot of fun to watch what Lubos has to say if and when some of his senior colleagues start working on LQG, something that seems entirely possible since string theory is now moribund, whereas LQG is in a much livelier state.

Landscapeology still seems to be making headway at taking over particle theory and ensuring that it becomes a pseudo-science. If you’ve got $250 and can get to an access grid facility, next week you can participate by video conferencing in a workshop at Ohio State on Strings and the Real World, which will have one day out of three devoted to the Landscape. I would have thought the title of the workshop would get into trouble with false advertising laws, since one thing that is clear is that absolutely none of the talks will be even slightly relevant to the real world.

For a horrific vision of where particle theory is headed, check out the website of the String Vacuum Project. The idea seems to be to get particle theorists spending their time developing software to do numerical computations searching amongst the infinite variety of the Landscape to find something or other. The section of the web-site on the connection of any of this to real particle phenomenology remains to be written.

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18 Responses to Cosmological Frontiers

  1. D R Lunsford says:

    Heat death via mathematicians.

    May they expand forever into nothingness!

    -drl

  2. Arun says:

    When the money and public support runs out, unemployed physicists can start landscaping businesses – “Calabi-Yau lawn service”, and so on. I’m sure there are some catchy names to be had.

  3. Quantoken says:

    No no no. How could they do landscaping business. They have too many choices for customers, 10^500, and they have not built a single landscape yet.

    The money will run out much sooner than one expects. There is already a US Congressional House Resolution about this huge paradigm shift. See also Apollo Alliance.

    What these string theorists can do, is pitch the research on dark energy in hidden dimentions as a viable research on sustainable alternative energy source to replace fossil fuel. And there will be huge fund for it. Not that I believe in these stuff. But people like Kaku have proven themselves to be good salespersons and good advertisers.

    Quantoken

  4. hack says:

    This is an uplifting post. I’ve never felt better about leaving physics behind.

  5. logopetria says:

    “[Arkani-Hamed] said that he believed the cosmological constant was anthropically determined…”

    Can I just check what people like Arkani-Hamed mean by this? To say that some parameter X is ‘anthropically determined’ means that out of lots of different worlds (or universes), each having a different value of X, we know that only those with particular values of X will be habitable – and so obviously that’s what we observe. Is that right?

    So, for example, the Earth’s distance from the Sun is ‘anthropically determined’, because there are other planets, some are closer to their stars, some further away, and life will only arise on those that are at roughly the right distance. So ‘anthropic determination’ is a statistical selection effect (selecting from a large, already existent set of possibilities), rather than anything resembling a mechanism for fixing a parameter to a value?

  6. Nigel says:

    “The idea seems to be to get particle theorists spending their time developing software to do numerical computations…”

    Monte Carlo methods and even just numerical integrations of hard to solve anayltic functions are fun. Also, why not just fit a wave equation to the group behaviour of particles (molecules in air) and talk sound waves? Far easier than dealing with the fact that the sound wave has an outward pressure phase followed by an equal under-pressure phase, giving an outward force and equal-and-opposite inward reaction which allows music to propagate. Nobody listens to music, so why should they worry about the physics? Certainly they don’t listen to explosions where the outward force has an equal and opposite reaction, too, which in the case of the big bang tells us gravity. Far better to stick to horseshit computing.

  7. Chris Oakley says:

    Hi logopetria,

    Right.

    Anthropically determined = Not determined by our theories.

    Landscape = We give up. Tell us, God, how does your universe work?

    Spacetime has N dimensions, where N > 4 = Our theory doesn’t work, but we don’t want to admit it.

    (You get the general idea).

  8. Dissident says:

    Speaking of moribund string theory, I assume everybody’s noticed that Clifford Johnson over at comsmicvariance has now given undead theory a face:

    http://cosmicvariance.com/2005/10/30/chewing-things-over/

  9. Juan R. says:

    In standard particle physics exists something called vacuum. In the opinion of some of us that ‘vacuum’ is irreal and NEWER experimentally verified. This is easily proven via a number of recent published advances (e.g. Rev. Mod. Phys. 1995 67(1) 113-155). Then what play the role of the traditional vacuum of QFT? Hoyle/Narlikar theory explains us that the vacuum is really the ‘thermal-bath’ generated by the rest of the universe. Hoyle/Narlikar theory is a generalization of Wheeler/Feynman absorber theory.

    In Hoyle/Narlikar theory, a single ‘quantum vacua’ means a single environment. Since there is only a single environment in the observed universe, i see difficult how one could claim the existence of multiple vacua!

    About anthropy insanity, the best criticism i found on this topic was from M. Gell-Mann. I do not remember exactly the quote -i think that i read in his The quark and Jaguar book- but was some like

    I newer found a version of the anthropic principle that was not trivial or absurd

    P.S: Hoyle/Narlikar theory has been already extended -in press- for accounting some recent work in experimental failures of standard field theory and further mathematical research

    see PRE 1996 53(5) 5373, Phys. Lett A 1990, 146 (1,2) 6, etc.

    Juan R.

    Center for CANONICAL |SCIENCE)

  10. Kyle says:

    Why would this post make you feel better about leaving physics, Hack? It isn’t as if HEP or theoretical HEP is particularly important to physics anymore.

  11. Chris says:

    It is difficult to avoid the conclusion that Arkani-Hamed and many theoreticians of his generation are primarily technicians. They have mastered a huge array of sophisticated formalisms and techniques, and they want to exercise them.

    “So, we have a MSSM with 105 free parameters? Great, get us some data, and we’ll fit them to it. String theory leads us to the Landscape? Don’t worry about it, and certainly don’t waste time reflecting on what it means; get on with developing techniques to explore and characterize it. We impressed our elders and established our careers by getting good at this stuff, so let’s keep doing it and expand our repertoire.”

    That’s what theoretical particle physics is becoming, five years into the 21st century. The bigger the labyrinth the better; it just gives everybody more to do.

  12. Adrian Heathcote says:

    This anthropic stuff continues to baffle me and I feel a little bit like Gell-Mann.

    Isn’t the point that it is simply an example of our being able to rule out some theories because they will conflict with a pretty obvious fact about the universe, namely that we are here to make observations and theorise. It’s a crude prediction that any true theory must make.

    So the AP is just a coarse sieve to winnow out obviously false theories.

    Which makes it baffling: how have people been able to invest it with an almost mystical significance? And why did anyone swallow it in that form?

    cheers

  13. Syksy Rasanen says:

    Peter, what did you think of Burt Ovrut’s talk on building realistic models in string theory?

  14. woit says:

    Adrian:

    “Which makes it baffling: how have people been able to invest it with an almost mystical significance? And why did anyone swallow it in that form?”

    Good questions. I’d claim it’s because the string theory unification program has failed, but its proponents refuse to admit this. With a theory on their hands that can’t predict anything, they’ve turned to anthropism in desperation to avoid admitting failure.

    Syksy:

    I didn’t listen to the whole talk. Every so often I try and check out what progress has been made on this problem of getting the standard model. The kind of thing Ovrut is talking about has been pursued by many, many people for 20 years. My understanding of the current state of affairs is that they can, through a rather complicated construction, get something which at low energies is just the MSSM and lots of moduli fields. The problems with the moduli fields are well known. Their methods don’t seem to allow them to calculate a single one of the 125 or so parameters of the MSSM, or predict anything about supersymmetry breaking. This all looks to me like what you expect to happen if you pursue a wrong idea: by complicating things enough you can reproduce some of the gross features of nature, but no matter what you do you can’t come up with a real prediction, or even a convincing postdiction.

  15. logopetria says:

    “[String theorists have] turned to anthropism in desperation to avoid admitting failure.”

    This is something I still don’t understand. As Adrian (implicitly) asks, what is there to the “anthropic principle” aside from “agreement with particular observed facts”? How does the fact that the universe is habitable rule out any theory, except to the extent that the theory has already failed to agree with other observations (about the coupling constants, particle masses etc)?

    OK, so here’s a way it could be different. Given a theory that fails to predict some quantity, one thing you could do is just put in the exact value of that parameter by hand, and show that the theory can at least accommodate it. But instead of that, you could do something different – you could just put in by hand the fact that these parameters lie within a certain range (i.e. the range required for life). That’s a weaker constraint, but it might force some predictions out of the theory. So, for example, your theory might say: “If the speed of light has to be within a range compatible with life, then the only allowed value turns out to be exactly c“. Then, it seems, something anthropic-looking would appear to be doing some predictive work. Is that what’s going on?

  16. D R Lunsford says:

    Chris – re “technicians” – yes indeed, this was pointed out to me by my advisor – the machinery is so dense that you can crank out work without even thinking. Of course the latter is what goes missing, and without that one gets boredom.

    These technicians also tend to rely on cults of personality, lacking as they are in the necessary mental wattage.

    -drl

  17. dan says:

    “possible since string theory is now moribund, whereas LQG is in a much livelier state.”

    so what is the current story on
    1- string theory entropy for “ordinary” BH’s
    2- LQG on BH (with the discussion of transcedental numbers and ln2 versus ln3)
    3- do LQG still predict wavelength-dependent photon velocity deviations of c? — something that could be “tested”

  18. Juan R. says:

    Adrian

    If you are devoted the best years of your life to a head horse.

    If you are popularized your wrong theory in mass media before verifying that was correct -somewhat as cold fusion scandal- and moreover have used dishonest actions -as saying not the true, hidding the flaws of the theory, etc.-

    If you have claimed in almost every talk, paper, popular book, etc. that people against string theory was either stupid or ignorant.

    Then you have only two ‘exists’.

    1) Intelectual suicide

    2) Continuous negation of evidence

    It is interesting how some string theorists begin to claim that the problem of prediction is not with string theory. It is with our incorrect understanding of prediction.

    Since string theory does not fit basic requirements of science. String theorists, who do not choose option 1 of above, are claiming that we may change scientific method!!!

    This is a pure nonsense and reflects desesperation of the field

    Ironic question: When Kaku will propose the travel of all humanity to an alternative ‘elegant’ universe where string theory fits data?

    Juan R.

    Center for CANONICAL |SCIENCE)