Quick Links

Well worth reading is High Energy Colliding Beams; What Is Their Future, by Burton Richter. Richter is one of the pioneers of designing and building colliders, and he starts off by recounting some of the history. About proposals for a 100 TeV collider he comments on the challenges of doing this at high luminosity and the danger that the cost will be prohibitive (one thing I haven’t seen in these discussions is cost estimates), and asks why there is no large-scale program to develop low-cost high-Tc superconducting magnets.

He’s critical of the film Particle Fever on the same grounds discussed here (its portrayal of the only possibilities as being SUSY or the multiverse). About the multiverse, he writes:

There are two problems with the landscape idea. The first is a logic one. You cannot prove a negative, so you cannot say that there is no more to learn. The second is practical. If it is all random there is no point in funding theorists, experimenters, or accelerator builders. We don’t have to wait until we are priced out of the market, there is no reason to go on.

For some mathematics news, first there’s the announcement from the Flyspeck project of the completion of a formal proof version of the proof of the Kepler Conjecture by Thomas Hales. Hales is in Berkeley this week talking about something unrelated (the Langlands program) at an introductory workshop for this semester’s MSRI program on geometric representation theory. I’ve been watching some of the videos of the workshop talks, all of which have been quite good.

Also in Berkeley this semester is Peter Scholze’s course, with video of the first lecture here, notes here.

In yet more Berkeley news, in December they’ll host a mathematical physics workshop on Mathematical Aspects of Six-Dimensional QFTs. Better understanding the 6d N=(2,0) superconformal theory and its implications for various lower-dimensional phenomena is the main target here, a topic that will also be discussed here in the spring (where the 6d theory is called “Theory X”).

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21 Responses to Quick Links

  1. HL-LHC or HE-LHC says:

    High Energy Colliding Beams; What Is Their Future, by Burton Richter – what is a better investment, HL-LHC or HE-LHC? upgrading injectors or upgrading the magnets?

  2. Peter Orland says:

    I’m sure Richter understands this much better than I do – but I don’t see how high-T_c magnets would help. Isn’t a huge cryogenic facility needed to pump the tunnel down to a good vacuum? I thought cooling the magnets was relatively insignificant. An accelerator physicist would certainly know the answer.

    I also thought that there were some fundamental problems with making powerful high-T_c magnets anyway (friction of vortices moving through in the material? ceramic machining?). Anybody out there know?

  3. Peter Woit says:

    HL-LHC or HE-LHC,

    It seems highly likely CERN will go ahead with HL-LHC. My impression is that the cost of that is much less than an HE-LHC project. The latter would require 27km worth of new superconducting high-field magnets, I’d assume this is very expensive. Not as expensive though as digging a 100km tunnel and equipping that with magnets, which is why Richter is worried that a 100 TeV machine may carry an impossibly high cost.

  4. Casey Leedom says:

    Thanks for the reference to Burton Richter’s paper. It was wonderfully readable and enjoyable for its long-term take on the history and future of beam colliders. I wish more papers like this were written by the “old men & women of science.”

  5. Martin says:

    @Peter Orland: if superconducting magnets can be run at the desired amperage without having to use liquid Helium, then this would obviously save a lot of money. High-Tc materials that superconduct at liquid nitrogen temperature (77 K) are known, but building strong and large magnets with them is still a challenge, due to a too low critical current.

  6. Peter Orland says:


    Hi Martin,

    Yes, liquid nitrogen costs the same as milk, so it would save money. But isn’t that a small fraction of the cost of the liquid helium already needed to produce the vacuum? My impression was that most of the cryogenics is needed after preliminary pumping, to properly evacuate the tunnel. If that’s true, perhaps more money would be saved inventing a better high-vacuum method (if such a thing is conceivable. I got nuthin’).

    I recall something similar about the low critical current of high-T_c superconductors (due to dissipation of moving vortices? I am not sure), but I thought another problem was machining. The materials are ceramics, so making coils would also be a problem.

  7. anonimous says:

    From LHC insiders and people involved in data analysis, I heard that a lot of persons are not happy about the HL program, given the negative results of run 1 in terms of new particles. If the could, they would push for HE, but they cannot stop the train anymore. Accelerator physicists worked a lot on HL and now it is impossible or impractical to change to HE. In their dreams, a lot of analysts wish to have HE.

    Moreover, HL means challenging backgrounds at the limit of the detectors, triggers and analysis techniques which risk to damage new particle searches. PP collisions are already dirty enough…

    A discovery in Run 1 would have been much better for this program and as we stand now, HL might turn in a nightmere. Anyway, I do not know the future and maybe they turn on LHC@8TeV and new states pop out easily…
    Let’s wait and see, but HE would have been much better.

  8. rss says:

    In the interests of procrastination, I looked into Peter Orland’s question. I think the short answer is, the beam line indeed has to be maintained partly at cryogenic temperatures, to achieve the ultra-low vacuum required. But the volume of the beam lines is “only” 150 cubic meters, whereas the volume of the insulating vacuum for the cryomagnets is 9000 cubic meters. So if high Tc superconductors could be made practical for this purpose, the cost savings could be significant.


  9. Peter Orland says:


    Thanks for looking into it. It sounds like a sensible answer…

  10. Anonyrat says:

    Ha, seems like the next great accelerator will be built on Pluto! (33-55K surface temperature).

  11. HL-LHC or HE-LHC says:

    since there’s no sign of SUSY or DM @ 8TEV, I would think HE-LHC would be the better ROI over HL-LHC with limited funds

  12. Peter Woit says:

    HL-LHC or HE-LHC,
    I think the point is that with limited funds one can’t afford HE-LHC, at least not anytime soon (but I haven’t seen any cost estimate for HE-LHC, this is a guess).

  13. J.F. Moore says:

    Peter Orland,

    There are many technologies to achieve the ultrahigh vacuum required to reduce scattering to a negligible level for LHC or future colliders. LHC for example uses ion pumps and non-evaporable getters in the ‘warm’ non-cryo sections. CLIC is one proposal for a linear collider that uses normal conducting RF, so no need for cryo facilities at all. Modern turbomolecular pumps are more than capable of reaching the required vacuum, its just a question of scale and expense and system maintainability.

  14. srp says:

    Nice to have Burton Richter supporting my-oft made and nearly always ignored point that the only rational course of action on the energy frontier is to put major effort into advanced accelerator concepts such as wakefields. Peter even managed to skip that primary takeaway in his summary, but here is Richter’s bottom line:

    “I am both more optimistic and more pessimistic about e+e- colliders. More optimistic because accelerating gradients of more than 50 GeV per meter (50 TeV per kilometer sounds even more exciting) have already been demonstrated in plasma- wakefield acceleration and of several GeV per meter in laser acceleration, though both have now poor 6-dimensional phase space; more pessimistic because I don’t see a push to develop these technologies for use in real machines. The e+e- colliders have two advantages over the proton colliders. The cross sections of interest are all of comparable orders of magnitude. The background of 10 billion or more uninteresting events for each interesting one, the problem of proton colliders, does not really exist for the electron colliders. There is a low transverse momentum fizz that is confined to small angle, but the interesting events are much easier to get at. In addition the equivalent mass reach in the electron colliders only requires 10% to 20% of the energy of the proton collider with the same mass reach. The 100-TeV p-p collider is matched by a 10- to 20-TeV electron collider. My challenge to the electron accelerator community is to produce a cost effective system with an acceleration gradient of at least 1-GeV per meter with reasonable transverse phase space and an energy spread of no more than 10% to 20%. Because of the parton distribution in the proton, the effective energy spread in p-p collisions is more like 100%. You have about 15 years to do it since that is the time to when HL- LHC will start to operate.”

  15. plm says:

    About the multiverse/anthropic principle/landscape:

    The electroweak standard model has parameters just like vacua in the string landscape are. Yet it makes lots of predictions/postdictions.

    Picking a vacuum assuming the anthropic principle (or not) still leaves alot of predictions from string theory, independent of vacuum-picking -which have so far proved wrong, for the nonpostdiction part.

    Assuming the anthropic principle is really more of philosophical attitude, empty of consequences. It has probably very little effect on how research is conducted. People (will continue to) try to understand better string theory or whichever theory they like, hoping to constrain more their predictions. Any sensible researcher liking the anthropic principle will not give up his research because of this as far as I can tell -I may be wrong, if you have examples please share.

  16. Ray says:

    Hi Peter, off-topic question but I think one in which you take an enormous interest – do you have any idea when the Planck polarization results are going to be published? I had heard a rumour that they were going to be published around September 1.

  17. Peter Woit says:

    I don’t know about “enormous”, if so I might have better sources of info about this… From what I’ve seen, what’s publicly known is that this conference


    to discuss the results has been scheduled for a long time for December 1-5. In many places I’ve seen “late October” mentioned for the release of the data that would be discussed at that conference.

    Frank Wilczek on twitter and Peter Coles on his blog had very definite rumors about an early release of data specific to the question of the BICEP2 patch of sky. It’s now long past the dates claimed in those rumors, and getting to the point that it would not seem to make sense to have two closely spaced releases, so at the moment, my uninformed guess is that “late October” is when we’ll hear something.

  18. Shantanu says:

    Peter, something OT.
    are you planning to attend David Gross’s colloquium at NYU this week?
    If you do, let me know how it was.

  19. Bob says:

    Nice to see about the formal proof. I’ve always wondered why this hasn’t been done more, after all who knows how much of mathematics has errors that have gone undetected, it would hardly be the first time …

  20. Peter Woit says:

    I hadn’t noticed that was happening. Unfortunately I’ll be teaching at that time, can’t attend. Maybe someone else will report.

  21. Franck Nadaud says:

    Dear Professor Woit, greetings from Paris, France !

    Here is a paper about high energy particle accelerators and log-periodicity:


    What is interesting are the figures about costs, but the paper is in french althrough an english version may have been published in a geography review.

    The paper was presented at a seminar in France about “scale relativity theory” of the french astrophysician Laurent Notale.

    However, the figures relate energy levels of past accelerators and costs in current dollars I guess.

    All the best regards.


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