Strings 2009 Out of Juice?

Posted on June 23, 2009 by woit

I had a suspicion that Strings 2009 wasn’t going to be scientifically very active, since not much has been going on in that field recently, but I still found it surprising how little news from the conference was making its way out to the internet. The conference is nearly half over, no evidence of any activity has appeared on the conference web-site, and until now I couldn’t find anything at all on the internet discussing what is going on there.

However, something did just turn up. Over at the Bad Astronomy and Universe Today Forum, under the topic heading “Off-Topic Babbling”, there have been two communications from Terry Giblin. In the first, written on Sunday, Terry writes that he’s on the road to Rome for the conference, and since it looks like he’ll be late, he’d like someone from the stage or audience to call him on Skype so he can ask the opening speaker (David Gross) a “strings question on quantum tunneling and singularities.”

That doesn’t seem to have worked out. In his latest communication, he says that he finally did make it to Rome, where he reports:

It would appear that I have not missed much over the past two days, yesterday the internet at the conference was only working slowly.

Today they had a power outage, so the conference was cancelled.

I hope I have more success tomorrow or the coming week.

Its amazing to think you can change the outcome of a conference, without being physically present……….

Update: A twitter from Marco Baumgartl has made it out to the internet, bringing more confirmation of problems:

I’d loved to give you live updates from the Strings 2009 conference, but they have severe wifi problems there, can’t connect

Update: An anonymous correspondent attending the conference reports that disorganization is a problem, and that there have been no major announcements. David Gross’s talk listed 8 fundamental problems for string theory and gave the string community a grade of A-F for progress on each problem (this sounds familiar, I vaguely recall him giving such a report card at some other talk a few years ago, I wonder if the grades have changed…)

The atmosphere was much like in other recent years: some disillusionment in the air, but people continuing to work along similar lines. The talks were described as sketchy and mostly incomprehensible to much of the audience, with many of the younger string theorists rather bitter about the lack of much of an attempt on the part of the speakers to give clear explanations and put their work in any sort of context (the audience of 450 has widely varying backgrounds, this is not a specialist conference).

Update: Well, the conference is over now, but still no slides of talks, or any blogging from anyone there, other than Jacques Distler’s attempt to find someone to go to dinner with a week ago. Reports I’ve gotten from the conference describe Vafa’s talk as “Good, in fact too good to be true”, and claim that Arkani-Hamed showed up two hours late for his talk, then went over time by 20 minutes.

Update: Still nothing on the conference web-site about the talks, or on blogs. Physics World does have a report from Edwin Cartlidge, who noted that the scientific talks were appropriately held at the University of St. Thomas Aquinas, named after the great Scholastic philosopher. He also reports on the public talks held yesterday. Witten appears to have decided the best thing to do was to not talk about string theory, but instead talk about particle physics, the LHC, dark matter and supersymmetry. He left string theory to Brian Greene, who somehow convinced Cartlidge that what this is all about is “that 10500 is somewhat bigger than 10120, and that’s a measure of how much we don’t understand dark energy.”

Greene pointed out that string theory requires an extra 6 (or 7) dimensions of space in addition to the three that we are aware of. Helpfully, these dimensions are so small that we can’t see them, but unhelpfully there are rather a lot of ways of curling these extra dimensions up – some 10500 different ways as it turns out. And we would have to study all 10500 if we want to find out whether or not string theory describes the real world.

For Greene, all is not lost, however. He pointed out that 10500 is somewhat bigger than 10120, and that’s a measure of how much we don’t understand dark energy. In a nutshell he argued that if we happen to live in one of the few of the 10500 universes where conditions are just right for us to exist then there’s a damn good chance that we could have such an apparently statistically unlikely dark energy. For Greene, this suggests we might be on the right lines with string theory. Others may be less convinced.

Update: The exponent problem has been fixed.

Posted in Strings 2XXX | 33 Comments

Gina Says

Posted on June 23, 2009 by woit

At the height of the string wars a couple years ago, one of the participants was a mysterious anonymous commenter going under the name “Gina”. Earlier this year Gil Kalai wrote to me to reveal that he was the person behind “Gina”, and that he had put together a book based on these blog discussions, to be entitled “‘Gina Says,’ Adventures in the Blogosphere String War”. He has now put the first part of manuscript up on his blog, the posting is here.

Back in January he sent me a copy of what he had written, I haven’t checked to see what changes might be in the version available now. Instead of writing something about this here now, I think I’ll just include part of my e-mail to him back in January, which gave my reaction to the project then:

Hi Gil/Gina…

Thanks for sending me the draft of the book. I read through it quickly, amused to relive again some battles of the string wars. When people ask me if I’ll write another book, often I’ve answered that I was considering just cutting and pasting together a lot of things from my blog, other blogs, and my e-mail, all of which told a rather amazing and often amusing tale. Funny to see that you’ve done something a bit like this yourself. During this period I also remember often telling people that I felt like I was living in a comic novel.

Actually, I’ve no intention of publishing anything about the “String Wars”, although happy if other people want to. I’m rather glad that they have died down, and I’m trying to devote my time instead to a research project I’m quite excited about (the BRST stuff I’ve started writing about on the blog).

Some comments about issues you raise, and some added context for some of these stories:

In my book, I tried to avoid saying much at all personally critical about string theorists and their behavior, the sort of thing that Lee Smolin did more of. I generally agree with what Lee wrote, but, in the past my personal contacts with string theorists were mostly with quite reasonable people that I didn’t think it appropriate to criticize in this way. After my experiences in the “string wars” though, I ended up feeling that Lee actually didn’t go far enough; that, individually and as a community, there are very real behavioral and ethical problems in how all too many string theorists do business. My impression is that the “string wars” brought a lot of this out into the open, and have damaged the perception of string theory among physicists and the wider community, more so than anything Lee wrote. Like Lee, what I was hoping our books would lead to would be a serious discussion of the issues involved. There was some of this, but all too much name-calling and bad behavior.

Some context about Clifford Johnson: independently of each other, both Lee and I wrote to him when our books were in draft form, asking if he would be willing to take a look at them, and let us know if there was anything we had wrong. He just ignored my e-mail, and I gather Lee got a similar response. He appears to be a rather nice guy, and I found this response kind of odd, it was one reason for my mistaken guess that he was the Cambridge referee. I still find his behavior exceedingly strange: how can you write long blog entries denouncing books you refuse to read? He seems to have an ability to refuse to acknowledge the existence of inconvenient realities that goes beyond anything I’ve seen before.

…

In your fantasy of the future, you mention my book being translated into Czech. Funny, a publishing company there did buy the rights a year or so ago, and I think they will be bringing it out. Sometimes reality and fantasy are indistinguishable in this story…

Update: There’s a posting about this over at Physics World.

Posted in Uncategorized | 30 Comments

Templeton Foundation Strategy and Planning

Posted on June 22, 2009 by woit

Most physicists are rather dubious about whether “multiverse” research is deserving of any support since it’s not clear that it is even science. Because of this, such research has been finding financial support in recent years not from conventional sources like the NSF, but from the Templeton Foundation, a very wealthy organization devoted to the goal of bringing together science and religion. Some examples of this funding include the World Science Festival program mentioned in the last posting, and the Foundational Questions Institute, which provides grants, many of them for multiverse research.

I’d always wondered if there was some kind of organized effort by Templeton to push this kind of research, and and got a partial answer to this question recently when I took a look at some of their web-pages. Last year they organized two days of conferences at the Royal Society in London, associated with their choice of cosmologist and Catholic priest Michael Heller for their 2008 Templeton Prize of a million pounds. The preparatory readings page of the second day’s conference provides a link to a document entitled Towards the Establishment of the Philosophy of Cosmology at Oxford. There’s also a link to “Password Protected Papers” on the topic of Toward a New Philosophy of Cosmology, but these papers aren’t really password protected since the password (“multiverse”) as well as the user name (“universe”) are given right next to the link.

If you follow this link, you are taken to the web-site for “A Strategy and Planning Workshop of the John Templeton Foundation”, held in May 2007 at the Royal Society. The purpose of this workshop is described as:

To bring cosmologists and philosophers together to review the ‘state of the field’ of the philosophy of cosmology and to explore the most effective ways of developing and enriching the philosophy of cosmology. How might the John Templeton Foundation contribute to field development?

and here are some other extracts from that page:

The John Templeton Foundation would like to help develop this field. We are considering the creation of substantial research support opportunities in the philosophy of cosmology. In addition, our expectation is that there is some need for infrastructure, and the Foundation would be interested in helping to support development of a suitable context for a flourishing field….

…the afternoon session, a discussion of strategy for field development. The Foundation is serious about providing resources if we can find a strategically-effective plan to make a difference.

This afternoon session was described in the program as follows:

Goal: Finally, we explore what is needed to develop the field of philosophy of cosmology in a dramatic way over the next decade. Our initial thought is that the field needs some infrastructure development as well as basic research support. Because this work must bring together such disparate fields, it is not easy working through basic university structures. It may be that beyond core research projects, we need to support the creation of major long-term initiatives or centers, and help establish training for a new kind of scholar as well as faculty positions and perhaps other elements of infrastructure such as book series or a journal to take two common elements of the scholarly enterprise. Also needed, perhaps, are ways of making it more visible to the public in ways that improve on current popular presentations.

The afternoon talks were by Priyamvada Natarajan, a Yale astrophysicist described as “currently a member of the advisory panel for the Dialogue on Science, Ethics, and Religion of the American Association for the Advancement of Science (AAAS) and has an abiding intellectual interest in understanding issues in spirituality and science”, and 2004 Templeton Prize winner George Ellis who is described as “co-author of On the Moral Nature of the Universe: Theology, Cosmology, and Ethics” and “editor of the Far Future Universe: Eschatology from a Cosmic Perspective.” The respondent was the Reverend Keith Ward, described as “his main work is a four-volume comparative theology from OUP”, and “His most recent book, published in 2006, is Pascal’s Fire – religious understanding and scientific faith.” The evening program was devoted to a celebration of Bernard Carr and the book based on three Templeton-funded conferences that he edited, Universe or Multiverse?

In a whitepaper prepared for the strategy session, Carr argues not just for the anthropic principle, but for the necessity of a “new science”:

In one sense the current debate today about the scientific status of M-theory and the multiverse proposal is nothing new. We’ve seen that progress on the outer and inner fronts has always been controversial, so perhaps history is just repeating itself. However, there is another sense in which the current situation is very special. This is because today — for the first time — the boundaries at the largest and smallest scales have connected. They are unified through quantum gravity and so the two science/philosophy frontiers have merged.

One might argue that this merging represents the completion of the scientific process. This is why the symbol of cosmic uroborus is so powerful: it represents both the evolution of our knowledge of the universe and the triumph of physics in producing a unified view of the world. Have we therefore reached the endpoint of science just as the macroscopic and microscopic frontiers merge? I doubt it. Personally I believe this merely represents a transformation in the perceived nature of science.

He then explains why Templeton money is needed:

Whether one redefines science to include exotic new ideas is not just a semantic issue. It also has practical implications because research in topics deemed to be “unscientific” is unlikely to be funded through the usual channels. For example, even in my own field, I have sometimes found that I cannot obtain a grant for a research project because some funding council has changed the definition of what constitutes “astronomy”. There will always be research areas (especially cosmological ones) which straddle the border between science or philosophy and this is why JTF’s initiative to support such areas is so important. It can promote or nurture ideas which have not yet been accepted into the world of legitimate science.

Carr is a past president of the Society for Psychical Research, and in its proceedings recently published a paper entitled Can Psychical Research Bridge the Gulf Between Matter and Mind?. In the white paper he advocates the idea that Consciousness is somehow part of this new science:

Another feature of the new paradigm – and here I am definitely venturing beyond the boundaries of current science – is likely to be mind. One feature of the Universe which is noticeably absent in the current paradigm of physics is consciousness….

…even the mention of the C word was taboo until recently. On the other hand, one might be sceptical of physicists’ claim to be close to a “Theory of Everything”, when such a conspicuous aspect of the world is neglected.

Certainly physics in its classical form cannot incorporate consciousness….

But what has this to do with cosmology? At first sight, developments in cosmology and particle physics might appear to have diminished the status of mind. The more we understand the Universe, from the vast expanses of the cosmos to the tiny world of particle physics, the more irrelevant humans (and hence minds) seem to become. Curiously, however, in recent decades cosmology has brought about a reversal in this trend, suggesting that mind may be a fundamental rather than incidental feature of the Universe. I’m referring here primarily to the Anthropic Principle…

He ends with some comments on theology, beginning with:

Of course, most scientists are even more uncomfortable straying into the domain of theology than philosophy, so the G word (God) is usually regarded as even more taboo than the C word. However, since science seems to be coming to terms with the A and C words, perhaps the same will happen with the G word. Maybe there is a gradual process of desensitization in which the A, C and G words become successively accepted!

The whitepaper by Ellis deals with the crucial question of whether untestable speculation is science:

There is also a reverse flow, whereby the development of the philosophy of cosmology – pushing the philosophy of science to its limits – may well have useful influences in wider realms of philosophy. Indeed it must be so, as cosmology helps us understand the nature of being human by clarifying the overall physical context through which we come to have our existence. So a useful part of the whole enterprise may be to try to develop that link: the different ways in which our understanding of the universe helps shape our views of humanity, and the ways that the philosophy of cosmology may help shape the philosophy of science. This may be particularly useful in terms of those aspects of physics which also face problems of testability for fundamental reasons, and so where some physicists are proposing to lessen the degree of rigour usually demanded in a scientific proof, decrying usual scientific criteria of testability as they do so (string theory comes to mind).

The whitepaper of Simon Saunders is an earlier version of the proposal for a new Oxford program available on the 2008 conference site. It proposes a new masters level 2 year course in philosophy of cosmology, with Templeton funding 2 3-year postdocs, a 5-year research fellow, a visiting scholars program, buy out time for those teaching in or administering the program, and funding for fellowships for graduate students. He also proposes to spend about 20,000 pounds a year on an outreach program to promote “philosophy of cosmology” in schools.

I haven’t seen any evidence that this planning and strategy session led to anything. For one thing, there does not seem to yet be a “Philosophy of Cosmology” program at Oxford, although perhaps Templeton will at some point fund such a thing. But, this session does give a good idea of where some people would like to take theoretical physics, and indicates Templeton’s interest in the idea of heavily funding ventures to promote such a “new science”.

On a somewhat related note, see today’s PZ Myers posting entitled The name “Templeton Foundation” needs to become a mark of failure.

Posted in Multiverse Mania | 31 Comments

Manufacturing universes in a fractal multiverse

Posted on June 21, 2009 by woit

I gather that the World Science Festival here in New York a week or so ago was a great success, although I was out of town for most of it. The one part of the program I was dubious about (Infinite Worlds) seems to have come off even more one-sided than planned, since David Gross couldn’t be there.

There’s a report on this at Ars Technica from someone who was sitting near Cameron Diaz while watching the program. Philosopher of science Nick Bostrom did point out the obvious, that for the multiverse to be science it has to predict something. Someone seems to have convinced the author of the piece that there actually is such a prediction:

Early in our Universe’s history (before the mulitiverse’s inflation pulled things apart), it was possible that the Universe bumped into a neighboring one. If that’s the case, there should be remnants of that event buried in the cosmic microwave background. Less than a month from now, the ESA’s Planck mission should arrive at the L2 Lagrange point with instruments sensitive enough to pick up this signal.

So, I guess in a couple years from now, we’ll know if there is a multiverse or not…

For another report, see here.

Sean Carroll reports here on some other parts of the festival, including the panel on Time Since Einstein, where he explained to the audience that “the fact that an a splattered egg cannot turn back into a pristine unbroken egg is the best evidence we have that we live in a multiverse.”

Posted in Multiverse Mania | 10 Comments

News from CERN, Witten Interview

Posted on June 18, 2009 by woit

The new CERN Bulletin is available, and it contains a link to a recent video interview of Witten, who has been visiting CERN during the past year.

Some other things in this issue:

  • Bill Gates recently visited the LHC, bringing his son Rory. Gates announced:

    I just bought the rights to the Feynman ‘Messenger Lectures’ that he gave in Cornell [University] in the 1960s. The BBC filmed Feynman giving what I think are the best physics lectures I have ever seen. So we are going to make these lectures free for anyone to watch.

  • There’s news about the LHC restart here and here, including the warming up of sector 4-5 discussed in postings here recently. Here’s what Director General Heuer has to say:

    The bottom line is that we remain on course to restart the LHC safely this year, albeit at reduced energy.

    A tremendous amount of work has been done to fully understand the splices in the LHC’s superconducting cable, one of which was the root cause of the incident last September that brought the LHC to a standstill. We’ve learned a great deal. It’s mostly good news but there’s also plenty of food for thought. The good news is that all the measurements done so far indicate that we will be ready by September or October to run the LHC safely at around 4-5 TeV per beam. If new evidence appears in the meantime to suggest otherwise, we’ll modify the energy for this year’s run accordingly. The food for thought is that the same tests tell us that before we can run safely above 5 TeV, more work is needed, and this will be carried out in a shutdown starting in Autumn 2010.

    Many of you will have heard, or seen on the LHC web pages, that we’re warming up sector 4-5. This sector can be warmed and re-cooled within the time remaining before we inject the first beam of 2009 into the LHC, and doing so will give us increased confidence that we fully understand the splices. We’re warming up this sector because we have developed a new non-invasive technique for investigating the splices. The sector has been measured at a temperature of 80K, indicating a suspect splice or splices. By warming the sector, the results of the test can be checked at room temperature, thereby validating the procedure at 80K. If the 80K measurements are validated, any suspect splices in this sector will be repaired.

    From this, it sounds like the current plan is to not wam up the cold sectors, but reach a decision on what the highest energy they can safely run at in case of a quench, given their understanding of remaining problems with bad splices. This might mean running below the planned 5 TeV/beam.

  • On July 1 CERN will be providing training for its employees on how to deal with the press.
  • On July 2 there will be a talk by Steve Myers on the LHC status

    • Update: While the CERN DG indicates readiness of the LHC for start-up in “September or October”, the most up-to-date schedule (which somehow came into my possession this morning…) shows powering tests in sectors 4-5 and 8-1 going through the end of October, so machine checkout and first beam not until the beginning of November.

    Update: There’s now a press release. According to this, they are now planning to start up at some energy in the range 4-5 TeV, currently 2-3 weeks behind schedule (so start-up second half of October).

    Posted in Experimental HEP News | 4 Comments

    Summer Programming

    Posted on June 18, 2009 by woit

    As far as academics are concerned, summer has started, which means that there are lots and lots of conferences going on. The past couple weeks we’ve had two here in the Columbia math department, one in algebraic geometry, and another covering various related topics in hyperbolic geometry and knot theory.

    Next week 450 or so physicists will gather for the big annual string theory conference, and a couple weeks ago there were more than 400 participants at the big annual SUSY conference, SUSY 2009. For more on this, see reports from Jester and Sabine. Jester’s take on the conference included:

    Over 400 participants, not counting squatters. 42 plenary speakers, most of whom witnessed the glorious days when supersymmetry was conceived. Seven parallel parallel sessions to cover every aspect of supersymmetry that has not yet been covered thoroughly enough. Royal coffee break menu fully adequate to the royal conference fee. And so on and on since 16 years and into the future.

    Meanwhile, there is no single hint from experiment that supersymmetry is realized in nature… but that should not upset anyone. As my fellow blogger skillfully put it, supersymmetry is the “shining beacon”, the “raison d’etre” and for this reason “the conundrum is how it will be discovered, not if”. That’s why every year we come together to enjoy old familiar faces and old familiar talks. The point is, while waiting for the inevitable, to maintain that kind of spirit that David Lodge praised in his books.

    At Santa Cruz this week, there was a conference in honor of the 60th birthdays of Tom Banks and Willy Fischler, blogging from David Berenstein.

    At Penn there’s a summer school on Geometry of Quantum Fields and Strings, blogging at Rigorous Trivialities.

    On the multiverse front, Thibault Damour has a survey article about constancy of physical constants, where he makes the reasonable argument that checking such constancy is one of our few ways of getting insight into the origin of these parameters of physical theory. Sometimes you see the claim made that string theory predicts time-dependence of constants (since they are moduli parameters), other times the claim is made that string theory does make one prediction, that such constants won’t change (due to energetics of the landscape). Damour summarizes this as

    However, there is no firm prediction for the observable level of EP violation. Actually, the current majority view about the “moduli stabilization” issue in String Theory is to assume that, in each string vacuum, the coupling constants are fixed by an energy-minimizing mechanism which is generically expected to forbid any long-range violation of the EP. This, however, makes EP tests quite important: indeed, they represent crucial tests of a widespread key assumption of string-theory model building. This exemplifies how EP tests are intimately connected with some of the basic aspects of modern attempts at unifying gravity with particle physics.
    Some phenomenological models (inspired by string-theory structures, or attempting to understand the cosmological-constant issue) give examples where the observable EP violations would (without fine-tuning parameters) be just below the currently tested level.

    The “string universality” principle discussed here recently is related to Leibniz’s “Principle of Plenitude”:

    all logically possible “things” (be they objects, beings or, even, worlds) have a tendency to (and therefore must, if one does not want contingency – be it God’s whim – to reign) exist.

    So, experimental measurements are important not because they can tell us whether string theory is right or wrong, but because they can tell us which kind of string theory is right….

    The latest Seminaire Bourbaki was last week, here’s a summary of the talks. Edward Frenkel has posted his survey of Gauge theory and Langlands duality on the arXiv.

    Earlier this week I learned from my colleagues one obscure piece of mathematical culture that I had been unaware of. Physicists have the famous story of how Alpher and Gamow brought in Bethe as co-author to improve the author list, but it turns out that mathematicians have a somewhat different story of this kind. At lunch one eminent algebraic geometer started snickering when someone (using standard terminology) brought up the well-known ring associated to an algebraic variety due to David Cox. At this, it was pointed out that Cox was co-author of a famous paper with Steven Zucker, and the story goes that this came about because Cox had decided once he heard of Zucker that a Cox-Zucker paper just was asking to be written. A supposedly authoritative source on the internet claims:

    Cox and Zucker were admitted as grad students to Princeton in precisely the hope that they would someday collaborate. This kind of forethought is why Princeton is Princeton.

    For a related mention of this, see the Journal of Improbable Research.

    Posted in Uncategorized | 14 Comments

    La Tête dans les Étoiles

    Posted on June 15, 2009 by woit

    This past weekend the city of Villeneuve-sur-Yonne organized a science festival entitled La tête dans les étoiles; les pieds sur terre! It featured Lubos Motl speaking on “Physics at the Planck Scale”, and the Bogdanoff brothers on “The Beginning of Time”.

    Posted in Uncategorized | 13 Comments

    String Universality Reloaded

    Posted on June 12, 2009 by woit

    I still haven’t figured out yet what the arXiv’s trackback policy is, since trackbacks to my blog entries sometimes appear there, sometimes not. One example in the “not” category is my recent posting about the Kumar-Taylor paper on “String Universality”, which now has trackbacks to postings by Jacques Distler (recently seen here) and Dmitry Podolsky. The ways of the arXiv remain mysterious, but I can’t help recalling that my original problems with them seemed to have to do with powerful people who did not like having their multiverse pseudo-science disrespected. Even without the trackback, I’m wondering if the authors of the paper somehow heard about my comments and felt they needed to be addressed, since a new version of the paper has just appeared.

    The most extensive changes are to the section on “predictivity” discussed in my posting. Here’s some of the added text:

    It may be that string universality holds for four-dimensional theories with supersymmetry, but that supersymmetry breaking mechanisms lead to a constrained subset of non-supersymmetric low-energy theories in 4D.

    It is possible that the dynamics of string cosmology may define a natural measure on the space of string solutions, which would favor some solutions over others. Currently, however, we lack a mathematically complete or background-independent formulation of string theory. It is likely that significant progress in this direction will be needed to understand the cosmological measure on the string landscape. In this brief discussion, we describe the situation for predictivity in the absence of such a breakthrough.

    Some other changes:

    This may seem like a very awkward situation for string theory.

    has been replaced by

    If we were living in six dimensions, then this would seem like a very awkward situation for string theory.

    and the assurance that string theory would explain anything seen at the LHC has been toned down a bit, with

    any new and unexpected phenomena found in experiments at higher energies should be realizable in the string theory context

    replaced by

    any new and unexpected phenomena found in experiments at higher energies may be realizable in the string theory context

    Posted in Multiverse Mania | 17 Comments

    Latest From the LHC

    Posted on June 9, 2009 by woit

    Last week was the annual Fermilab User’s Meeting, for all sorts of interesting talks see here. These included a talk by Sergio Bertolucci giving recent news about the LHC status. This week CERN is hosting a CERN-Fermilab Hadron Collider Physics summer school, talks here, including one from Jorg Wenninger about the LHC status.

    The main concern now involves bad soldering of some of the 1700 or so bus-bar inter-connections between magnets. One of these seems to have been at the origin of the accident last September. For the sectors (four of them) that are warm, such bad joints can be identified relatively easily, by their higher-than-normal resistance, and repaired. Unfortunately, for the four sectors that are now cold, identifying such bad splices is much more difficult. Warming up these sectors and cooling them back down is a time-consuming process that could significantly push back the LHC schedule.

    Late last week the decision was made to start warming up sector 45. Measurements at 80K had identified 3 cases of anomalously high resistance. The plan is to warm up the sector, take measurements which can be compared to the measurements made when the sector was cool, and fix splices as necessary. For this particular sector, things can be rearranged so that warming it up and cooling it back down will not seriously impact the schedule.

    For the other three cold sectors though, the situation remains unclear. They’re gathering more data and analyzing it, trying to understand better what is going on, as well as analyzing the question of whether it’s possible to go ahead and find ways to run the machine safely, even given the possible existence of somewhat iffy interconnections.

    The latest version of the schedule, from mid-last week, has powering tests ending in mid-October. So, as long as it does not turn out to be necessary to warm up more sectors, late October is the time-frame for trying again to circulate a beam and begin beam commissioning.

    Update: There’s a video of Wenninger’s talk last week available here, where he gave some more details in the question session afterwards. Sector 45 will be warm and ready for measurements next Monday (June 22). If the results show good correlation with what was measured at 80K, at the end of the month the temperature of the three remaining sectors will be stabilized at 80K and measurements will be made on those.

    About the current schedule for when to try and circulate a beam, he says “I know that officially it’s still September [last week] but I have problems to sell that…” with a better guess of sometime in October (assuming the three sectors at issue don’t need to be warmed up). He also remarks that it will be a while (2012?) if ever before the machine operates at 7 TeV. 5 TeV is the likely energy at the beginning, with a possibility of going up to 6 TeV.

    Posted in Experimental HEP News | 17 Comments

    String Universality

    Posted on June 7, 2009 by woit

    There’s a new paper out on the arXiv this evening, advertising a new concept called “string universality”. The authors argue that in six dimensions, by use of appropriate compactifications, any consistent 6d supergravity theory has a string theory realization. They go on to conjecture that the same might be true in four dimensions. As for the implications of “string universality”, they write:

    If it is correct, or even close to correct, that string universality holds in six dimensions, then in this case we seem in some sense to be in the worst possible situation vis a vis low-energy predictions. If every possible consistent theory can be identified from low-energy considerations, and all of these theories can be realized in string theory, then string theory would seem to have no predictive power for low-energy physics…

    Not being able to predict anything sounds bad for string theory. But wait, they go on to explain why not only is this not a deadly problem, it’s actually a “strength of the theory”. You see, there’s “symmetry and elegance” to a principle that is consistent with absolutely everything and constrains nothing. Some worrywarts might have problems with such a principle since it can’t be tested, but, just because something can’t be tested doesn’t mean it’s not right, no?

    This may seem like a very awkward situation for string theory. It should be emphasized, however, that there is no reason a priori why a theory of quantum gravity relevant at the Planck scale of 1019 GeV should make any prediction for physics at the scale of 1 TeV, 16 orders of magnitude below the quantum gravity scale. String theory is valuable as a framework for describing quantum gravity. If in fact, string theory can be used to provide a UV completion of essentially any low-energy theory whose coupling to quantum gravity does not violate some basic principle like unitary via anomalies, this can be seen as a strength of the theory. There is a certain symmetry and elegance about the notion of a quantum gravity theory which provides for the production of essentially all possible low-energy behaviors in some regime of the theory or region of the metaverse.

    If indeed, string theory can give rise to such a wide range of low-energy behavior that predictions at the TeV scale cannot be made precisely, it may bother some scientists that this makes the theory difficult to test. But, on the other hand, this does not make the theory any less likely to be correct. It just makes it more difficult to verify.

    Posted in Multiverse Mania | 28 Comments