Quick Links

Just returned from a few days in Boston, will try and catch up here on various topics:

  • This past week I was able to attend some of the talks at the conference in honor of David Vogan’s 60th birthday. I’m still trying to make sense of Bernstein’s talk on Stacks in Representation theory, where he argued that the category of equivariant sheaves on a certain stack is a better-behaved construction than the category of representations. I’ve always wondered whether this would be helpful in the case of representations of a gauge group, where the stack has something to do with equivalence classes of connections. It was his first use of Beamer, and some slides went by too fast. I noticed that a few people were documenting talks for themselves with phones/tablets taking pictures of slides/board.

    Among the other interesting talks, Jim Arthur discussed the conjectural automorphic Langlands group, along the lines of this older paper. He indulged in some speculation I’d never heard before, that Langlands functoriality might imply the Riemann hypothesis (somehow by analogy to something from Langlands about the Ramanujan conjecture appearing in Deligne’s proof of the RH in the function field case). Unfortunately the laptop being used to show his slides decided to start installing Windows Updates two-thirds of the way through his talk. For whatever reason, I didn’t manage to follow his comments at the end of the talk about something new having to do with Weil’s explicit formula in number theory. Consulting with some experts later though, I couldn’t find anyone optimistic about the Langlands implies RH speculation.

  • Also last week, the draft P5 report on a strategic plan for US HEP over the next 20 years was released, with discussion at an HEPAP meeting. Besides planned LHC upgrades, high priority goes to neutrino physics based at Fermilab, with a plan to attract more international participation. Other directions getting a high priority are on-going dark matter experiments and CMB research. A continued move of funding from research grants to construction projects will likely keep pressure on grants to university theory groups. Research into muon colliders is down-played, with a recommendation to “consult with international partners on the early termination of MICE.”
  • Skepticism about the BICEP2 primordial gravitational wave claims continues, with for instance this story at Science, and this preprint. In retrospect, it’s curious that the possible problems with foregrounds did not get more attention at the time of the original high-profile announcement.

    See here for a Caltech workshop on the BICEP2 results. Andrei Linde’s talk started with his complaining about the popular and textbook coverage of inflation. He said that when journalists call and ask him what BICEP2 will tell us about Grand Unification, he responds “nothing”. At the end of the talk, Sean Carroll asked him about the multiverse, with Linde’s response emphasizing what a great thing it is to have a theory that can’t be disproved:

    If you cannot disprove it, then you have this powerful weapon of thinking about and explaining things around you in an anthropic way.

  • This coming week here in New York there will be lots of events associated to the World Science Festival. One aimed not so much at a popular audience that I’ll likely attend will be a day-long Symposium on Evidence in the Natural Sciences, which will be at the Simons Foundation. It will end with a discussion between Jim Baggott (author of the recent Farewell to Reality) and Brian Greene (sold out now I fear).

Update: The Princeton crowd now has a preprint out, with the detailed argument that BICEP2 can’t distinguish “gravitational waves” from “galactic schmutz”, see here.

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9 Responses to Quick Links

  1. Bernhard says:

    The anecdotal arguments Linde uses to “defend” eternal inflation at the end of the talk are something else. Who needs to confront experimental data when you can talk about black and white footballs?

  2. Curious Mayhem says:

    Indeed. The tensor polarization result doens’t prove or disprove eternal inflation; it is consistent with it, but consistent with some other kind of inflation.

    The disappointment about eternal inflation is that it excludes overt quantum gravity considerations almost by design, while dovetailing with GUTs, of course. Avoiding the emptiness of string cosmology, quantum gravity means a Wheeler-DeWitt equations that includes the inflaton. Shades of the 1980s. This is more interesting scientifically.

  3. TonyK says:

    Your “Farewell to Reality” link is missing a colon.

  4. Neil says:

    Was Linde’s comment made with his tongue in his cheek, I hope? I find it hard to believe he seriously thinks that a theory that cannot be tested, even in principle, can be explanatory.

  5. Peter Woit says:

    You can judge for yourself, the exchange with Carroll starts at about 1:49:35 in the video I linked to. He sounds serious to me…

    Thanks, fixed.

  6. Nick Gresham says:

    Would the slides of Bernstein’s talk be available?

  7. Peter Woit says:

    Unfortunately Bernstein’s slides haven’t been posted, perhaps someone can get them from him, or get one of the organizers like Pavel Etingof to do so.
    On the other hand, Arthur’s slides are now there, so people can see more about his comments on functoriality and the Weil explicit formula.

  8. A.K. says:

    indeed the ‘quasiclassical’ approach to the RH has a hidden Langlands-like structure; it is a mystery to me that nobody saw it until now (apparently).

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