Witten in Canada

Edward Witten is in Canada this week, giving a series of lectures at the Fields Institute, the mathematics institute at the University of Toronto. He’s also giving a public lecture at the Perimeter Institute in Waterloo.

The first of his lectures in Toronto, on the topic of Relativistic Scattering Theory is now available on-line. It’s a nice, simple explanation of scattering theory, using the “geometric quantization” point of view about quantum field theory. For a quantum theory of a real scalar field, one chooses a complex structure on the space of solutions of the free field equation, making this a priori symplectic infinite dimensional manifold actually a Kahler manifold. Witten’s next two lectures in Toronto will be on “Gauge Symmetry Breaking” and “The Quantum Hall Effect”.

I’m curious what he’ll be promoting in the public event at Perimeter on Wednesday. Will it be string theory? Will anyone ask him about the appalling nonsense his fellow string theorists were spouting there all last week?.

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12 Responses to Witten in Canada

  1. Quantoken says:

    Peter said: “The problem with the multiverse is not that it invokes things you can’t directly observe, the problem is that it predicts nothing about anything.”

    I would accept any indirect observation as a legitimate observation of nature, as long as the observation can be consistent and has the potential of rule-out/rule-in certain theoretical models. The problem is even INDIRECT observation of multiverse is impossible. It simply does not interact with our universe in any way that is observable, or at least not in a way that allows us to speculate any property of the multiverse.

    Anything that does not deal with objective observation of this particular universe we know, is not science.

    On a side note, I think it is pretty stupid for us to send THREE presidents to the funeral of a leader of a private religion, in a tiny country embbeded in a country full of street mafias and burglars, at a time when 100 other national heads also gather, in an era that we constantly face terriorist threats. It’s recklessly dangerous and do no good other but provide a golden opportunity to those who want to do harm.

    Frankly I do NOT think they have any significant police force to provide any meaningful protection in any way, shape or form, in such a complete chaos when a couple million people around the world all want to rush in to see the Pope, including the one who attempted on his life in 1981!!! I can only hope that nothing bad happens.


  2. Peter Woit says:

    Hi Mark,

    I took a look at the Spergel talk and the discussion afterwards. What really amazed me were the people trying to defend the whole multiverse nonsense by claiming it was just like the situation in the sixties with the quark model, which posited entities one couldn’t see. This is really absurd. The quark model made all sorts of predictions which could be tested by experiment, most notably the prediction of the existence and properties of the Omega-minus. The problem with the multiverse is not that it invokes things you can’t directly observe, the problem is that it predicts nothing about anything.

  3. robert says:

    1+2+3..=-1/12, surely. Still, what’s a factor of two amongst theorists.

  4. Mark says:

    On an unrelated note see the discussions on anthropic
    principle, multiverse and string theory after David Spergel’s
    talk at STSCI on dark energy

  5. D R Lunsford says:

    Dear ____,

    The point is, the existence of this Kaehler manifold is apparently equivalent to the need for antimatter. See this thread from SPR:



  6. Carl Brannen says:

    Dear Dr. Wotit,

    Around 5 years ago, I picked up a two-volume textbook on string theory that was supposed to be the most widely used text for graduate classes and figured that I would update myself on QFT. I was horrified to discover that the iffy premise of analytic continuation (as mentioned in the Witten lecture) had been replaced by dimensional regularization. Before I had gone more than a few dozen pages the author was had summed 1+2+3+… to get -1/6, which reminds one of divergent series analysis from the early 20th century, but was not what I expected a theory of everything to provide. So I decided to begin studying QFT again, to see if I could bring the standard model into a generalization of the Dirac wave equation.

    The analytic continuation of the electron from past to future reminds me of the fact that the handedness of anti-particles are the opposite of the handedness of the spinors that represent them. In order to generalize the Dirac equation into a Clifford algebra equation, I had to use the handedness of the spinors rather than handedness as it is usually defined. Instead of conserving angular momentum, in this language, the usual interaction vertices conserve the difference between the handedness of the particle spinors and the handedness of the antiparticle spinors.

    Anyway, it was interesting to see Witten’s lecture.


  7. Alejandro says:

    BTW quantoken, I like the aspect of your new journal.

  8. Anonymous says:

    An entire lecture by Witten (I was hoping for something more profound) leading up to… crossing symmetry? How anticlimatic!

  9. Quantoken says:

    No need for dark energy

    Have a look at my latest blog entry, where I talked about the possibility of “dark energy” being just the regular baryon matter, distributed throughout the voids of the universe, in the form of micro meteorites that’s hard to detect but yet constitute 70% of the mass of the universe.

    Click here.

    BTW it is also a better blog server than username.blogspot.com. I encourage people, like Lubos et al. to use livejournal instead of username.blogspot.com.


  10. DQOTD says:

    Dumb Question of the Day:

    If T, C or P is not a symmetry, then does the holomorphic S defined on Sym(r+s) H_C acquire additional interesting structure?

  11. Alejandro says:

    So, after all, Witten surrenders string theory and promotes barebones QFT.

  12. D R Lunsford says:

    Very interesting. Compare Feynman’s Dirac Memorial Lecture (reproduced in the little Dover book “Elementary Particles and the Laws of Physics”).


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