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  1. J

    A Vacuum pair creations on the light-cone

    That is of course what I mean: pair creations under large electric fields, which is why I brought it up in the context of the Casimir effect. The usual interpretation is as pair creation from vacuum . The pair got separated by a large enough electric field. The "borrowed" energy of the virtual...
  2. J

    A Vacuum pair creations on the light-cone

    Thanks. Those are interesting articles. It seems that most of what I have read on QFT (including several textbooks) and heard use a sloppy description. That's unsettling.
  3. J

    A Vacuum pair creations on the light-cone

    You are right, I was thinking of Schwinger pair creations. Apologies. I see also that the Casimir effect is not interpreted anymore in term of vacuum energy. Things have evolved since I learned about QFT...
  4. J

    A Vacuum pair creations on the light-cone

    Right, the language of Dirac sea is outdated, which is why I put it in quote. I am sorry for using an old image. But surely, that there are virtual particle creations out the vacuum, which can be materialized if a field is present, is still a fact: That is the basis for the Casimir effect...
  5. J

    A Vacuum pair creations on the light-cone

    When a field is quantized on the light front, there is no possible pair creation from the vacuum energy. This is because kinematic operator P^+ generates only a positive spectrum ( https://en.wikipedia.org/wiki/Light_front_quantization#Spectral_condition ). So there is no "particles popping out...
  6. J

    A Gluon spin and quark confinement

    Thank you. I was thinking of the heavy (static) quark, quenched, approximation that is e.g. studied by lattice QCD. This is a simple case to picture the confinement mechanism, although as you say it does not contains the full story: the QCD string appears to break down when light quark...
  7. J

    A Gluon spin and quark confinement

    Gluons are spin 1 particles so the Strong Force can both attract and repulse. The constituent partons of a meson are a quark and an antiquark so they must carry a given color and its anticolor, respectively, in order that there is no net color carried by the parton. In that case, the force...
  8. J

    A What is the meaning of chiral-odd/chiral-even functions

    Thank you. So in better terms than what I used, it means that when one switches the right handed quarks in a nucleon with the left handed ones, a chiral-odd distribution function switches its sign while a chiral-even one retains its sign. Is that correct?
  9. J

    A What is the meaning of chiral-odd/chiral-even functions

    I read about quark distribution functions in the nucleon that are chiral-odd or chiral-even functions (Sivers function, Boer-Mulders function and other distribution function related to nucleon transversity). What is the definition of chirality for functions? Does this mean they are odd or even...
  10. J

    Free electron beam inducing an EM field in a target?

    Many mechanisms can induce an electromagnetic field in materials. Which ones are the most relevant depends on the electron energy. You should say what energy you have in mind. The response frequency of the material will certainly be the same as the pulse of your beam but this can be masked by...
  11. J

    Path integrals

    Zee's Quantum Field Theory in a Nutshell is a great book to start on path integrals and QFT in general. (I stopped counting how many times I read it).
  12. J

    Deur's modified gravity: a type of MOND inspired by QCD

    The theoretical justification for Deur's work is that gravitons carry energy-momentum and since gravity couples to energy-momentum (including rest mass, although it is zero for gravitons), then a graviton can directly couple to another graviton. This has been known for a long time. In the early...
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