LHC Startup at 10 TeV

Robert Aymar, the Director General of CERN, has announced that the LHC will operate when it starts up this year at an energy of 5 TeV per beam (10 TeV total center of mass energy), rather than the design energy of 7 TeV per beam. To operate the LHC magnets at the highest current and get to 7 TeV requires a time-consuming sequence of powering tests and quenches, so the decision was made to put this off until the winter shutdown. With this decision, the process of beam commissioning can start soon after all sectors have been cooled down, and this is now scheduled for mid-June. Beam commissioning should take two months, with first physics collisions thus scheduled for late summer.

It remains possible that problems will be found during or after cooldown that will require warming back up one or more sectors, and this would lead to a delay of a couple months or so. The last sector scheduled to be cooled down is 4-5, which is now warm to allow repair of the defective triplet magnets. Whenever a sector is warmed up, a major problem is damage to defective PIMs which then need to be replaced. If there are too many of these, a delay in the cooldown is possible. The search for damaged PIMs relies on a “sputnik” tennis-ball-like sensor sent through the beam-pipe. Latest news is that 4 damaged PIMS have been found so far.

Update: I’d been wondering how much extra work this change in energy would cause for the experimentalists, just saw a posting about this by Gordon Watts, entitled Start Your Monte-Carlo Engines!

Posted in Experimental HEP News | 17 Comments

Krauss on Boltzmann Brains

Lawrence Krauss has a piece this week in New Scientist about the latest hot topic in theoretical physics, Boltzmann brains. It’s entitled String Theory’s Latest Folly, and starts off:

THOMAS AQUINAS may never have actually wondered how many angels can dance on the head of a pin, but his tortured musings about metaphysical issues associated with the non-corporeality of angels (and the related issue of whether there is excrement in heaven) stretched the limits of reasonable rational inquiry so far that later scholars invented the phrase to mock him.

My thoughts turned to Aquinas last week as I sat through a lengthy seminar on the subject of Boltzmann brains. The speaker decided his ruminations were so important that he needed 90 minutes rather than the customary hour. To my surprise, many in the room seemed to agree with him.

He goes on to explain what this is all about:

The problem is that statistical arguments suggest that in long-lived universes, far more Boltzmann-brain consciousnesses will develop than intelligences like our own, which have evolved over billions of years. That would mean we are far from typical, so anthropic explanations of our universe fall by the wayside.

Some theorists have therefore tried to develop constraints that would force all inflating universes like our own to decay well before Boltzmann brains can infect them. The bad news here is that in this case our universe must be unstable, and heading for a catastrophic end. But at least anthropic arguments from string theory would not be undermined. You can decide for yourself which you would prefer.

and to conclude:

If debating angels dancing on pins marked the intellectual low point of medieval theology, then we may similarly question the merits of debating problems that require hand-waving arguments involving unknown quantities that differ by billions and billions of orders of magnitude. Let’s focus on other issues, at least until better theories come along.

Update: At Lubos Motl’s blog, there’s a comment from Krauss noting that the title was chosen by an editor, not by him, and that he agreed that it was misleading, since the piece was not specifically about string theory.

Posted in Multiverse Mania | 18 Comments

Off-topic

I usually try hard to avoid writing here about anything not directly related to mathematics and physics, but on rare occasions I can’t resist. Many readers may want to skip this posting as unserious, but maybe some will find it entertaining.

My travels last week took me to Las Vegas, where I stayed overnight with my old housemate John Chang and his family. During my graduate student days at Princeton, one year I lived with two fellow physics graduate students who were part of a card-counting team which had started up to take advantage of the recent opening of casinos in Atlantic City. Many of the other members of the team were based at MIT, and my roommates often mentioned one of them, “John”. A few years later I was looking for a place to live in Cambridge, answered an ad, and ended up going to meet the owner of a house who was looking for a housemate. After we talked for a while, I realized that he was the “John” my Princeton roommates had been telling me about.

Anyway, you can read more about John in a story just put up at the Xconomy web-site. He’s the model for the character “Mickey Rosa” in the book “Bringing Down the House”, which has just been made into the movie “21”, opening this weekend (Kevin Spacey plays “Mickey Rosa”). I’m looking forward to seeing the movie on Saturday.

Update: For more about John and the card-counting business, see this article in Men’s Vogue.

Update: If you’re interested in this, you should definitely check out John’s blog, which he has started updating again with new postings.

Posted in Uncategorized | 22 Comments

2008 Abel Prize

The winner of this year’s Abel prize, a prize of over $1 million set up back in 2001 to provide an equivalent of a Nobel prize in mathematics, is…

Actually, I have no idea. If you know who it is, feel free to break any vows of confidentiality in the comment section here. Otherwise we have to wait until 7am EDT tomorrow morning, when the answer will be revealed here.

Update: The prize goes to John Thompson and Jacques Tits, for their work on finite groups. More details here, including the citations for Thompson and Tits.

Posted in Uncategorized | 21 Comments

Will Physicists Find God?

Today’s second most viewed article in Newsweek is an interview with Steven Weinberg about what we’ll learn at the LHC. Unfortunately it almost immediately turns into a discussion about religion and is linked to on the Newsweek site as Will Physicists Find God? The interviewer wants to know whether the Nobelist will be willing to reconsider his well-known atheism based on what is found at the LHC. Weinberg does a good job of answering these questions politely and sensibly. He gets a bit into philosophy of science, noting that the hypothesis of the existence of God is testable (in the same sense that string theory is testable), since thunderbolts coming out of the sky and striking atheists dead would give strong evidence that He (or She) exists.

Sean Carroll, quoting from a book by David Deutsch on parallel universes, attacks Weinberg as not understanding how science works in a blog posting about Science and Unobservable Things, and in a discussion with John Horgan at Bloggingheads entitled Cosmic Bull Session. He specifically is critical of a claim by Weinberg that “the important thing is to be able to make predictions”, arguing that such a statement is “going a bit too far.”

This month’s Discover magazine has a cover story on theories of what happened before the Big Bang. The article begins with St. Augustine speculating on what God was doing before the first day of creation, then moves to discuss the work of several modern “cosmology heretics”. The discussion doesn’t include the work of the Bogdanovs, but does cover three such theories, from Steinhardt and Turok, Carroll and Chen, and Barbour, ending up with a discussion of the crucial problem of testability of such theories. Steinhardt and Turok are rather concerned about this, and point to one negative prediction (shared by many cosmological models) that they can make: effects of gravitational waves will not be seen in the CMB polarization. Carroll and Barbour on the other hand don’t seem to have a problem with not being able to predict anything, with Barbour described explicitly as having “no way to test his concept of Platonia.”

For more recent research on the multiverse, see philosopher Klaas Kraay’s Theism and the Multiverse, where he argues that:

theists should maintain that the world God selects is a multiverse. In particular, I claim that this multiverse includes all and only those universes which are worth creating and sustaining. I further argue that this multiverse is the unique best of all divinely-actualizable worlds.

Posted in Uncategorized | 40 Comments

Media Events in Paris

Tomorrow I’ll be in Las Vegas, on my way to southern Utah, so will miss a couple of math-physics media events taking place in Paris. At 2pm on Sunday, Lubos Motl will be appearing at the France Television booth at the Salon du Livre, together with the Bogdanov brothers, to sign copies of his new book L’equation Bogdanov: Le secret de l’origine de l’Univers?. In other Lubos news, I recently heard a rumor that he is now the scientific advisor to the president of the Czech republic.

On Monday, a day-long symposium on the topic of how mathematics and physics are covered in the press will be held at the Institut Henri Poincare. One focus of the symposium is the celebrity exceptional Lie group E8, which last year kicked up media-storms for both the classification of unitary representations of its split real form, and for Garrett Lisi’s attempt to use it for unification. Jean Iliopoulos will be speaking on the topic of the hopes and controversies surrounding string theory, and I’d be curious to find out what he has to say about this.

Update: More information about the E8 talks here, Lubos’s impressions of Paris here.

Posted in Uncategorized | 37 Comments

Electric-Magnetic Duality on a Half-Space

The past few weeks I’ve often been going down to the IAS in Princeton on Thursdays to hear talks given as part of the special program there this semester in mathematics. These talks included a series of five talks by Witten; notes from David Ben-Zvi and Sergei Gukov are available here.

The first three talks concentrated on the existence of a very special superconformal six-dimensional QFT, and information that could be derived from what is known of its properties. Such a theory is an inherently quantum object, lacking a usual sort of classical limit or Lagrangian formulation. Witten compares it to the holomorphic conformal field theory that appear as “square roots” of the WZW model. These field theories are closely related to the representation theory of loop groups and at the core of a several important mathematical developments of the last couple of decades. The mathematical significance of the six-dimensional theory remains much more mysterious, and Witten argues that understanding this mystery is a very worth goal for both mathematicians and physicists. . For more about this, see the article Conformal Field Theory in Four and Six Dimensions, based on his lecture at the Oxford conference in honor of Graeme Segal’s 60th birthday back in 2002. Taking the six dimensions to be the product of a torus and a four dimensional space, the existence of such a superconformal six dimensional theory implies an SL(2,Z) symmetry of N=4 Super-Yang-Mills on the four dimensional space. This includes the famous Olive-Montonen non-abelian electric-magnetic symmetry that is responsible for Langlands duality in Witten’s 4d QFT approach to Geometric Langlands.

The last two talks of the series dealt with a different topic, boundary conditions in N=4 SYM. Taking this theory on the half-space with boundary conditions, one can ask about the implications of non-Abelian electric-magnetic duality for these boundary conditions. Witten has recently been working on this subject with Davide Gaiotto, he’ll be talking about it later this month at a Stony Brook symposium in honor of C. N. Yang and Jim Simons, and I assume a paper will appear sooner or later. In his IAS lectures Witten was talking to mathematicians and arguing that “universal” operations (ones that can be done uniformly for all Riemann surfaces) in geometric Langlands should all come from the properties of these boundary conditions. Note that in this work what appears is the full N=4 SYM theory, not just the topological twisted version. This theory plays a central role in AdS/CFT, so if new information about its physics arises from this study, this should be directly interesting for physics, although Witten did not discuss this in his talks.

The two sorts of boundary conditions that get related by duality are analogs of Neumann and Dirichlet boundary conditions. The Neumann boundary conditions involve superconformal 3d QFTs, examples of which were studied by Intriligator and Seiberg in their 1996 paper Mirror Symmetry in Three Dimensions. Witten has previously worked on this kind of thing in the Abelian case, see here.

During these visits to the IAS I got the chance to meet Meng-Chwan Tan, who is there in the Physics group this year. He has been working on a different QFT approach to geometric Langlands, one that is purely two-dimensional and based in conformal field theory, using (0,2) sigma models on flag manifolds, and has just posted a the revised for publication version of his paper on the subject here. This is much closer to the approach to geometric Langlands via conformal field theory that Edward Frenkel has described here.

In other geometric Langlands news, there was a workshop on Homological Mirror Symmetry recently in Miami, with notes from many of the talks available here (and a blog posting by Joel Kamnitzer here). And there’s another one (notes here from David Ben-Zvi) going on this week at the IAS. I better stop now, go and get some sleep so I can head down there tomorrow morning to catch the last day of it.

Posted in Uncategorized | 1 Comment

2008 Templeton Prize

The 2008 Templeton Prize was announced today. It goes to Michael Heller, a Polish cosmologist, philosopher and Catholic priest, for “sharply focused and strikingly original concepts on the origin and cause of the universe.” The full name of the Templeton Prize is the “Templeton Prize for Progress Toward Research or Discoveries About Spiritual Realities” Its goal is to promote bringing science and religion together by awarding a prize of 820,000 pounds sterling, the single largest award given to an individual. Prince Philip somehow gets into the picture too, since he will be presenting the prize to Heller in a private ceremony at Buckingham Palace in early May.

In recent years Heller has been interested in non-commutative geometry as way to study quantum gravity and cosmology. According to Heller, the crucial question of cosmology is “Can the Universe Explain Itself?”, and associated with the awarding of this prize, the Templeton Foundation will be hosting a discussion of the associated question “Does the Universe Need to Have a Cause?”.

The Templeton press materials describe Heller as “initiating what can be justly termed the ‘theology of science.'” His nomination for the prize says that:

It is evident that for him the mathematical nature of the world and its comprehensibility by humans constitute the circumstantial evidence of the existence of God.

I’m rather dubious about the way Heller mixes theology, philosophy and cosmology, but, unlike much harder-nosed physicists these days, at least he seems to recognize the problems with the Multiverse.

Heller intends to use the prize money to create a Copernicus Center in Cracow to further research and education in science and theology.

Posted in Uncategorized | 13 Comments

The Landscape and the Emperor’s New Clothes

The String Vacuum Project, described as “a large, multi-institution, interdisciplinary collaboration”, that has been established over the last few years, is having its Kick-Off Meeting next month at the University of Arizona. This group had submitted grant proposals to the NSF for funding of such a project in the past, but I don’t know if they ever managed to get NSF or other funding. They motivate the project by claiming that

Given that relatively large numbers of string vacua exist, it is imperative that string phenomenologists confront this issue head-on…

In this context “relatively large” involves numbers like 10500, 101500, etc.

Bert Schellekens has a web-site devoted to promoting the Anthropic Landscape, where he argues that

The String Theory Landscape is one of the most important and least appreciated discoveries of the last decades.

Besides the web-site, he has slides from two general talks on-line (here and here). In the talks he compares string theorists to the famous Emperor parading in no clothes, except what he is criticizing is those string theorists who have been unwilling to acknowledge the existence and importance of the anthropic landscape. He’s critical in particular of

those people claiming that they have always known that String Theory would never predict the standard model uniquely, but that they did not think this point was worth mentioning.

His modernized version of the fable of the Emperor goes as follows:

Many years ago, there lived some physicists who cared much about the uniqueness of their theories. One day they heard from two swindlers that they could make the finest theory which was absolutely unique. This uniqueness, they said, also had the special capability that it was invisible to anyone who was stupid enough to accept anthropic thinking.

Of course, all the townspeople wildly praised the magnificent unique theory, afraid to admit that anthropic thoughts were inevitable, until Lenny Susskind shouted:

“String theory has an anthropic landscape”

It’s not clear who he would identify as the “two swindlers”….

According to Schellekens, the “string vacuum revolution” is on a par with the other string theory revolutions, but most people prefer to overlook it, since it has been a “slow revolution”, taking from 1986-2006. The earliest indications he finds is in Andy Strominger’s 1986 paper “Calabi-Yau manifolds with Torsion”, where he writes:

All predictive power seems to have been lost.

and in one of his own papers from 1986 where the existence of 101500 different compactifications is pointed out.

Schellekens claims that “string theory has never looked better”, but he completely ignores the main question here, the one identified by Strominger in 1986 right at the beginning. If all predictive power is lost, your theory is worthless and no longer science. What anthropic landscape proponents like him need to do is to show that Strominger was wrong; that while string theory seems to have lost all predictive power, this is a mistake and there really is some way to calculate something that will give a solid, testable prediction of the theory. The String Vacuum Project is an attempt to do this, but there is no evidence beyond wishful thinking that it can lead to a real prediction. Schellekens has worked on producing lots of vacua and describing them in a “String Vacuum Markup Language”, and in his slides describes one construction that involves 45761187347637742772 possibilities. These possibilities can be analyzed to see if they contain the SM gauge groups and known particle representations, but this is a small number of discrete constraints and there is no problem to satisfy them. The problem is that one typically gets lots and lots of other stuff, and while one would like to use this to predict beyond-the-SM phenomena, there is no way to do this due to the astronomically large number of possibilities.

He lists goals for the future (“Explore unknown regions of the landscape”, “Establish the likelihood of SM features”, “Convince ourselves that the standard model is a plausible vacuum”), but none of these constitutes anything like a conventional scientific prediction that would allow one to test to see if what one is doing has any relation to reality. In the end, he comes up with the only real argument for the String Vacuum Project and other landscape research, that of wishful thinking:

… and maybe we get lucky.

Update: There’s a story about the String Vacuum Project in this week’s Nature by Geoff Brumfiel. It includes skeptical comments from Seiberg and yours truly, as well as Gordon Kane’s claim that:

evidence supporting string theory could emerge “within a few weeks” of the [LHC]’s start-up.

Update: At the blog Evolving Thoughts, there’s a discussion of whether theoretical physicists have now taken up a “stamp-collecting” model of how to do science. I point out that this is stamp-collecting done by people who don’t have any stamps, just some very speculative ideas about what stamps might look like.

Posted in Uncategorized | 70 Comments

HEP and Politics News

In perhaps the most important development for the future of HEP in the US in quite a while, yesterday Bill Foster, an HEP experimentalist who worked on CDF and the Recycler at Fermilab, won a race to fill the congressional seat being vacated by Dennis Hastert. This is the congressional district that includes Fermilab, and one of the main reasons for the disastrous budget cuts affecting Fermilab this year seems to have been the fact that the congressional representative for its district not only was no longer Speaker of the House, but had retired.

Foster managed to win as a Democrat in a district that has been a safe one for the Republicans, but he will be up for reelection in November, facing the same opponent. The House Democratic leadership will likely be doing whatever it can to support Foster, and this could very well involve changing its stance from cutting Fermilab’s budget to restoring it for next year, FY2009. This should hold true at least through the first week of November, although chances of a budget being passed by then don’t seem very high.

I’m still rather confused by news about how the LHC is progressing. A new schedule has appeared, but unlike previous versions, it just shows plans for cooling down the machine, with no information about plans for what happens after that. Earlier versions of the schedule included a period of 2-3 months of powering tests for each sector after it is cool, followed by a month for machine checkout, and two months for beam commissioning before collisions at 7 TeV.

The new schedule has most of the machine cool by the end of May, except for sector 4-5, which is now being warmed up for the repairs on inner triplet magnets, with powering tests already having been performed. This last sector is supposed to be cool again in mid-June. A review of the powering tests is here, from which I gather that discussions are underway about possible ways of speeding up the process for the other sectors, including the possibility of running the machine at 5 TeV rather than 7 TeV during its first year. This would evidently allow a quicker commissioning, avoiding time-consuming quenchings of the magnets that are part of testing them at the highest currents. The Resonaances blog has a report of a talk by Lyn Evans at Moriond this past week, where he describes the possibility of running at lower energy as the currently preferred option, and states that the current plan is for first collisions by the end of August.

For news about recent experimental HEP results, I’m afraid I can’t do better than refer you to Tommaso Dorigo for coverage and excellent discussions of a new, more accurate top mass measurement, reports of not very convincing deviations from the Standard model in B-mixing and charm decays, and stringent new limits on WIMPs that make SUSY more unlikely.

For other news about particle detectors, it appears that perhaps at some point in the future, one will be built into every memory chip made, to guard against errors caused by cosmic rays.


Update
: For a KITP talk on the current state of the LHC and prospects for the next year or so, by Michael Barnett of ATLAS, see here.

Posted in Experimental HEP News | 2 Comments