Trying to Keep Up

Super-busy at the CERN laboratory outside Geneva; lots of new data becoming public as it appears at the ICHEP conference, lots of theory papers flying around (not all of them accurate and uncontroversial) trying to interpret the Higgs measurements, and lots of work to do preparing the experiments for their further measurements of the Higgs and for their searches for other particles and forces.  Updates to this website are getting slotted in when possible.  In addition to my recent summary post from Thursday, I put up an article Friday about the data itself and why it is convincing [updated today with some new plots], and a new article today about how a lot of skill and a little luck led to the beautiful results we saw on Wednesday.  Enjoy!  [If you have friends asking you why the Higgs particle matters, you can have them read my article about it.]

12 responses to “Trying to Keep Up

  1. one of the first papers I looked at – from John Ellis and Tevong You

  2. Perusing Ellis & You’s paper “Global Analysis of the Higgs Candidate with Mass ~125 GeV” convinces me that both the Higgs field and the Higgs boson exist as predicted. Is there a Nernst field such that: (Higgs field) = (vacuum catastrophe field) — (Nernst field) ? If the answer to the preceding question is no, then what is the resolution of the vacuum catastrophe?

  3. Is the observed Higgs renormalizable or `merely’ effective, or is this question wrong-headed? If merely effective, then what’s the status of quantum gravity now?



    • This is not well-defined as a set of questions. Particles cannot be said to be renormalizable or not renormalizable; quantum field theories (with sets of particles and fields and their interactions) are the things that can be renormalizable or not.

      The current data does not tell us whether the quantum field theory governing the Higgs along with the other particles is renormalizable or not. (There are already hints from neutrino masses that it may not be, but that has nothing to do with last week’s discovery.)

      There is (and probably will be) no impact on the status of quantum gravity.

      • Matt: thanks. If the LHC data are consistent with a non-renormalizable field theory, then is not the principal objection to quantum gravity, namely that it is non-renormalizable, removed?

        • The theory of quantum gravity is just fine, if we treat it as an incomplete theory… a so-called “effective” theory, valid for processes below 10^18 GeV in energy.

          The goal of the LHC is to help us find the effective theory that applies at the TeV energy scale and perhaps somewhat above. Again, we expect it to be an incomplete theory — since it doesn’t include gravity, it won’t apply above 10^18 GeV in energy either, and may fail well below that for other reasons.

          The problem of quantum gravity is finding a *complete* theory — one that is *not* merely an effective theory and can be used at energies far above 10^18 GeV energies.

          So there’s no problem with having a non-renormalizable effective theory emerging from LHC data — it will just mean there’s more for us to learn about physics at higher energies in order to make the theory more complete. [We have a non-renormalizable theory for the interaction of hadrons and it works very well for energies well below 1 GeV; above (or below) 1 GeV we use the more complete theory of quarks and gluons.] And its non-renormalizability has no bearing on the need to find a complete theory of the world, fusing what we known about quantum field theory with what we know about gravity, and perhaps other things we don’t yet know.

  4. To a physicist, then, renormalizability is no more than a mathematical curiosity.

    • To a modern particle physicist, that is correct. It used to be considered to be important. The change in viewpoint occurred during the late 60s and 70s due to the work of people like Leo Kadanoff and Ken Wilson.

  5. Leonid Lerner

    This is a bit heretical.. There are countless books written in the 80s, 90s and now expounding the virtues of renormalizability as the basis for any good QFT. The reason Higgs proposed his boson was renormalizability (and unitarity). And I tend to agree ..

    • Unitarity is another matter — that is required.

      Renormalizability changed after Wilson — late 1960s, early 1970s. That was after Higgs wrote his paper; the fact that he had a motivation that we no longer see as essential doesn’t matter, the point is that he pointed out a suitable mechanism which is in fact the right answer. It may seem heretical to you, and to the books you are reading, but you had better read the modern books… for instance, Georgi on effective field theory, or Peskin and Schroeder, or Srednicki, etc. I’m at a workshop on Higgs physics and nobody giving talks here is insisting on renormalizability in their discussions…

  6. Leonid Lerner

    Hi Matt

    I had read both Peskin and Schroeder and some of Srednicki, and certainly I am familiar with the work of Wilson (I presume you means his 70s work on renormalization), but I have never got the message from it the renormalizability is irrelevant. It is in fact the fact the hidden symmetry theories a la anderson are renormalizable which led to belief in the weak interaction theory of Weinberg. And if that is still in the 70s, then t’hooft Noble prize was much more recent, in 1999. And what is it that he elucidated in “elucidating the quantum structure of the electroweak interactions in physics”, if it wasnt the renormalizability of Weinbergs theory (and QCD). I am sorry I am completely perplexed by your point of view.

    • Hi Matt & Leonid: your comments are fascinating but I suspect that the debate could best be continued productively and amicably in a neutral coffee shop. I would gladly pay for the coffee, on the condition that I could audit. May I however impose a last question, as before asked out of ignorance? Has an old problem such as the Uelhing shift been studied from the three perspectives of renormalized, effective and lattice field theories? I suspect that again my question may be wrong-headed but perhaps you could recast it more soundly.

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