LHC Update, More

Posted on January 29, 2010 by woit

According to John Conway, the decision coming out of Chamonix is to go with the first of the two scenarios described here: stay at 3.5 TeV/beam, then a long shutdown to fix all the splices. The idea is to run at 3.5 TeV during 2010 and 2011, stopping for shutdown either when 1 fb-1 has been accumulated, or end of 2011, whichever comes first. The LHC will thus be off throughout 2012, coming back in 2013 for a run at or near the design energy of 7 TeV/beam.

With the Tevatron counting on having around 12 fb-1 of data at 1 TeV/beam by October 2011, it should remain competitive with the LHC for many sorts of searches, including the search for the Higgs, for much longer than expected. This should be true for more than 3 years from now, until after the LHC has accumulated a significant amount of data at full energy in 2013. The current planning is for Tevatron operation only through FY2011, I wonder whether this will change…

Update: Science has a story from Adrian Cho here. The D0 co-spokesperson says the decision on running the Tevatron in 2012 “won’t have to be made for several months.” CERN experimenters are quoted as saying that they will still be searching for supersymmetry and extra dimensions. I haven’t seen any studies of exactly what 1 fb-1 at 7 TeV will make possible in terms of doing better than Tevatron limits on such processes and on the Higgs.

Posted in Experimental HEP News | 5 Comments

Are There Cosmic Microwave Anomalies?

Posted on January 28, 2010 by woit

No.

The WMAP team has just released a new set of papers based upon seven years of data from their experiment. For a summary of how this new data has sharpened some of their previous results, see the Cosmological Interpretation paper. They have also gone over claims by many groups to have found deviations from the standard cosmological model in their earlier data sets (for example claims to have found “the unmistakable imprint of another universe” which “points to string theory being on the right track.”) In a paper entitled Are There Cosmic Microwave Background Anomalies, the WMAP team reports:

In most cases we find that claimed anomalies depend on posterior selection of some aspect or subset of the data… We examine several potential or previously claimed anomalies in the sky maps and power spectra, including cold spots, low quadrupole power, quadropole-octupole alignment, hemispherical or dipole power asymmetry, and quadrupole power asymmetry. We conclude that there is no compelling evidence for deviations from the LCDM model

They give a humorous example of the problem that plagues typical claims to have found such anomalies, showing that the CMB sky map clearly contains the initials of Stephen Hawking, “aligned neatly along a line of fixed Galactic latitude.”

Update: For the WMAP team’s summary of its new results for the public, see here.

Posted in Uncategorized | 13 Comments

LHC Update

Posted on January 27, 2010 by woit

Those responsible for the LHC machine are having their yearly meeting this week in Chamonix to discuss the state of the project and plans for the future. Last week a subgroup met to discuss plans for beam commissioning to 3.5 TeV/beam, starting next month. The current schedule envisages beam commissioning to restart around February 19, and best estimate is that it will take about a month to establish safe, stable 3.5 TeV beams and begin extended runs for physics purposes. There’s a plan for a big media event when first collisions are achieved at 3.5 TeV/beam, something that may require discouraging experiments from announcing observation of high-energy collisions that happen before the planned moment (evidently this is what occurred last year, when Atlas saw 1.18 TeV/beam collisions before they were supposed to…).

This year’s schedule includes a possible one-month stop mid-year to increase the beam energy from 3.5 to 5 TeV, but based on the discussions at Chamonix, this looks very unlikely. The most serious problem with the LHC remains the bad splices which are known to exist in the machine, as well as sectors where definitive measurements of all the splices have not been possible (they would require warming up the sector, causing delays of months). The current knowledge of the splices leaves no room for error, even at 3.5 TeV, and going to 5 TeV would require warming up parts of the machine, something which cannot be done during a 1-month stop.

Discussions are beginning about how long a stop for repairs should be planned for after this year’s run ends in November. To be able to run at 5 TeV/beam will probably require keeping the machine off until May 2011 to fix splices. Going to the design energy of 7 TeV may require even more extensive work on the splices, work that could keep the machine off for all of 2011, with startup again in 2012. To get above 5 TeV, work also needs to be done on retraining the magnets through repeated quenches. Not much of this would be needed to get to 6.5 TeV/beam, but to go all the way to 7 TeV, problems that are still not understood with magnets from one manufacturer will have to be addressed.

Update: From the Chamonix summary talk, there are two main scenarios now being considered. In the first, the energy of the machine would stay at 3.5 TeV/beam this year and next, with .1-.5 fb-1 integrated luminosity in 2010, 1 fb-1 in 2011, then a year-long shutdown in 2012 to fix all splices before moving to 6.5-7 TeV/beam. In the second, splices would be fixed in stages, running for only 5 months in 2011, at 5 TeV/beam, 1 fb-1 integrated luminosity.

There will be a summary session at CERN next Friday.

Posted in Experimental HEP News | 13 Comments

Physics of the Universe Summit

Posted on January 26, 2010 by woit

The New York Times today reports on a Physics of the Universe Summit held a week or so ago in LA. According to the Times, participants stayed at “a Hollywood hotel known long ago as the ‘Riot Hyatt,’ for the antics of rock stars who stayed there.” Talks were a couple miles south at the SpaceX factory, Larry Page of Google was there “handing out new Google phones to his friends”, the magician David Blaine performed card tricks, and Bob Dylan’s son Jesse showed some sort of film about the LHC. The only other information about this that seems to be available on the web is Sean Carroll’s blog posting here, where he gives a link to the slides of his talk.

Optimist Gordy Kane claimed that the LHC will soon discover supersymmetry, making physics on the verge of seeing “the bottom of the iceberg”. Lisa Randall (who evidently has a new book planned about science and the LHC) argued instead for focusing on less grandiose small problems. She was skeptical about supersymmetry, pointing out that we should have seen various evidence of it by now, and that the “wimp miracle” of a stable superpartner explaining dark matter doesn’t work well “without some additional fiddling with its parameters.” Joe Lykken summarized the situation as:

We’re confused, and we’re probably going to be confused for a long time.

Posted in Uncategorized | 9 Comments

Various and Sundry

Posted on January 21, 2010 by woit
  • The latest New Scientist has an article about Erik Verlinde’s “entropic gravity”, with enthusiastic remarks from Robbert Dijkgraaf and Stanley Deser. Gerard ‘t Hooft expresses pleasure at seeing a string theorist talking about “real physical concepts like mass and force, not just fancy abstract mathematics”. According to the article, the problem with Einstein’s General Relativity is that its “laws are only mathematical descriptions.” I guess a precise mathematical expression of a theory is somehow undesirable, much better to have a vague description in English about how it’s all due to some mysterious entropy. There’s even an editorial about this:

    Now we could be closing in on an explanation of where gravity comes from: it might be an emergent property of the way objects are organised, much as fluidity arises as a property of water…. This idea might seem exotic now, but to kids of the future it might be as familiar as apples.

    In a new preprint, Lee Smolin uses Verlinde’s work in a very different way, to show that Newton’s law of gravity must emerge from the microscopic quantum gravity approach Smolin favors, that of loop quantum gravity.

  • Also on the New Scientist/entropy front, there’s a review by Craig Callender of Sean Carroll’s new book. I’d been wondering what philosophers of science would have to say about the book, and the reaction to Carroll’s multiverse explanation of the arrow of time was about what I suspected it would be:

    Daring to speculate in the absence of well-confirmed theory, Carroll jumps from clue to clue, from black hole physics to string theory to the holographic principle, until he arrives at his destination: an eternal “mother space-time” from which a multiverse of baby universes are continually bubbling up and pinching off. The mother space-time is a high entropy vacuum that gives birth to universes like our own, some of which we can expect to begin with low entropy. Problem solved, says Carroll, because that is natural.

    Carroll seems slightly embarrassed by the many leaps of faith he asks of his reader in proposing this solution, and the prose of Part IV sometimes reads like the pitch of an honest used-car salesman: “This car is a dream! True, the tyres are bald, brakes unsound and transmission sticky, but you’ll love it!”

    Carroll and other peddlers of multiverses make us an offer: we will explain the unexplained if you add vast unconfirmable matters of fact into your ontology. In this case that includes a host of disconnected baby universes, an eternal mother universe entirely unlike ours, and half a dozen unknown mechanisms to get all this working. Assuming this explains the low entropy past – and with so much unknown it is hard to be sure another conspiracy isn’t lurking within – is this a good deal?

    In most cases I don’t think so. Why is Manchester United perennially a good soccer team? Surely most solutions of the laws of physics don’t have them winning so much. How unnatural (and unfair) those initial conditions are! Nonetheless, a frothy sea of baby universes tempts no one. We shrug and say, that’s just the way it is. Sometimes it is best not to scratch explanatory itches.

  • Witten now has a long preprint out about his beautiful recent work on analytic continuation of Chern-Simons theory that I wrote about here last fall.
  • My colleague Johan de Jong has been working for a few years now on what he calls the Stacks Project, which aims at a detailed, foundational exposition of the theory of algebraic stacks, beginning with the necessary algebraic geometry. He has structured this along the lines of an open source software project, encouraging contributions to the project from other algebraic geometers. The latest addition to the project is a blog.
  • The filmmakers who brought us What the Bleep Do We Know? have recently completed a new film, entitled Ghetto Physics: Will the Real Pimps and Ho’s Please Stand Up!. According to Cornel West “This intelligent and intelligible film is a must-see for all of us.” There may be a theatrical release this year.
  • A huge proportion of the mathematics research literature is now controlled by the publishing company Springer Science + Business Media. Last April there were reports that the owners of the business had it up for sale for about $2.9 billion. The CEO denied these reports, stating “We are not for sale, there is no truth in Springer being sold”. Last month came the announcement that Springer was being sold, to two private equity firms from Sweden and Singapore. The price was about $3.4 billion, with the new owners also taking on $2.9 billion of the company’s debt.

    It’s not clear if there are any implications for mathematics publishing, with this perhaps just a transfer of control of the mathematics literature from one group of private equity firms to another.

  • In the next couple months Princeton University Press will publish a short new popular book on string theory, Steve Gubser’s The Little Book of String Theory. It is only 184 pages long and appears to be somewhat similar to efforts like The Complete Idiot’s Guide to String Theory, String Theory Demystified, and String Theory for Dummies, but less technical, with less graphics, and a lot shorter.

    According to the promotional material, the author

    describes efforts to link string theory to experimental physics and uses analogies that nonscientists can understand. How does Chopin’s Fantasie-Impromptu relate to quantum mechanics? What would it be like to fall into a black hole? Why is dancing a waltz similar to contemplating a string duality?

    and

    After reading this book, you’ll be able to draw your own conclusions about string theory.

    The introduction is available here, and ends with this description of recent debates over string theory:

    I don’t aim to settle any debates about string theory in this book, but I’ll go so far as to say that I think a lot of the disagreement is about points of view. When a noteworthy result comes out of string theory, a proponent of the theory might say, “That was fantastic! But it would be so much better if only we could do thus-and-such.” At the same time, a critic might say, “That was pathetic! if only they had done thus-and-such, i might be impressed.” in the end, the proponents and the critics (at least, the more serious and informed members of each camp) are not that far apart on matters of substance. everyone agrees that there are some deep mysteries in fundamental physics. nearly everyone agrees that string theorists have mounted serious attempts to solve them. And surely it can be agreed that much of string theory’s promise has yet to be delivered upon.

  • For two wonderful but very different short memoirs by mathematicians about aspects of their research work, see William Stein’s Mathematical Software and Me: A Very Personal Recollection, and Michael Harris’s A Mathematical Dream and Its Interpretation.

    • Update: The Onion carries the news that World Physicists Complete Study of Physics. The quote from a physicist is:

    Yeah, that about does it for physics. All done. Math can pretty much take it from here.

    Update: Robert Helling gives his take on the Verlinde paper here. It reminds him of a certain proof that reaches an unreasonable conclusion using the rules “time=money” and “money is the root of evil”. I noticed this via an arXiv trackback. Funny, for some reason there are no trackbacks to my postings on this topic

    Posted in Uncategorized | 17 Comments

    Big Think

    Posted on January 18, 2010 by woit

    A little while ago I did an interview for Big Think, and they just put it up here today, with some editorial comment here.

    I really don’t like watching or listening to myself, so I’m not about to go through the interview and see exactly how what I tried to say came out and later got edited. If I said something unclear or nonsensical, perhaps someone will let me know. Regular readers of this blog are unlikely to hear anything they haven’t read before. Big Think has their own commenting system, and you can comment there if you wish.

    Posted in Uncategorized | 17 Comments

    Particle Theory in Midtown

    Posted on January 17, 2010 by woit

    Particle theory is about to have a significantly higher profile in midtown Manhattan, with the launch of two new programs this spring:

  • The CUNY Graduate Center at 34th St. is starting up an Initiative for the Theoretical Sciences, with a program of colloquia, workshops and public lectures in various areas of theoretical science. In early April there will be a workshop on Emerging problems in particle phenomenology.
  • A few blocks away, at the 27th St. Stony Brook Manhattan campus, the Simons Center for Geometry and Physics will start having seminars February 12 under the title Simons Center Seminars in Manhattan.
    • Posted in Uncategorized | 4 Comments

    Templeton Foundation News

    Posted on January 15, 2010 by woit

    The Simons Foundation isn’t the only one announcing funding opportunities in math and physics. The Templeton Foundation’s list of funding priorities for 2010 is here, with applications opening February 1. In math and physics the topics they want to support research in are:

  • Quantum Physics and the Nature of Reality

    • and

  • Foundational Questions in the Mathematics Sciences

    • At least for 2010, they seem to have lost interest in the Multiverse.

    Templeton is also supporting a member of the Harvard Math Department in a big way, with a grant of $10 million to math professor Martin Nowak to fund a program in Foundational Questions in Evolutionary Biology.

    Posted in Uncategorized | 7 Comments

    Iranian Theoretical Physicist Assassinated

    Posted on January 12, 2010 by woit

    An Iranian theoretical physicist named Masoud Alimohammadi was assassinated in Teheran Tuesday. Alimohammadi’s publication list indicates that he began his career specializing in conformal field theory, and more recently had been working on questions in general relativity. Initial news reports inaccurately characterized him as a “nuclear physicist” and speculated that he was assassinated because of his association with the Iranian nuclear program, but there seems to be absolutely no reason to believe this.

    Posted in Uncategorized | 20 Comments

    The Entropy Decade

    Posted on January 11, 2010 by woit

    We’re only a week and a half into the new decade, but already I’m seeing a trend…

    A few days ago Sean Carroll’s book From Eternity to Here came out, promoting the idea that understanding time and cosmology is all about understanding entropy. The same day saw Erik Verlinde’s arXiv preprint On the Origin of Gravity and the Laws of Newton, which argues that

    Gravity is explained as an entropic force caused by changes in the information associated with the positions of material bodies.

    Verlinde is a well known string theorist, and the paper is somewhat of a repudiation of the motivating idea for string theory unification, that string theory predicts gravity since it has a spin two massless state. But even with the main motivation gone, all is not lost for string theory, since

    The presented ideas are consistent with our knowledge of string theory, but if correct they should have important implications for this theory as well. In particular, the description of gravity as being due to the exchange of closed strings can no longer be valid. In fact, it appears that strings have to be emergent too.

    This is discussed in blog postings here, here and here, and yesterday even made it to Slashdot.

    Today, it’s yet more entropy, with The Entropic Landscape by Bousso and Harnik, which propounds the Entropic Principle, that:

    the number of observers is proportional, on average, to the amount of entropy produced.

    and claims that this principle quantitatively predicts six important aspects of cosmology.

    While much of physics in the last century was dominated by a highly successful program to identify fundamental degrees of freedom of nature and understand their dynamics using increasingly deep and sophisticated mathematical formalisms, now the trend appears to be very different. Many of the most well-known theorists are pursuing research programs with the remarkable features that:

  • You don’t need to have any idea what the fundamental degrees of freedom are.
  • You don’t need any fundamental dynamical laws either.
  • You can do everything with high school mathematics.

    • The last century was a hugely successful one for physics, whether this new order will be equally successful remains to be seen.

    Update: More analysis of the Verlinde paper here, and Verlinde now has a blog and a twitter feed about it.

    Update: Verlinde is adding explanations of points in his paper and conducting a discussion of it on Lubos Motl’s blog here. He now says that, to explain quantum gravity

    I am not sure that string theory is the way to go.

    Even though under his new framework string theory explains nothing about any fundamental physics, Verlinde refuses to give up on it, arguing that:

    It should also be emergent, and it is nothing but a framework like quantum field theory.

    In fact, I think of string theory as the way to make QFT in to a UV complete but still effective framework. It is based on universality. Many microscopic systems can lead to the same string theory. The string theory landscape is just the space of all universality classes of this framework. I have more to say about it, but will keep that for a publication, or I will post that some other time.

    Posted in Multiverse Mania | 30 Comments