Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What does Weinberg–Witten theorem want to express?

  1. Dec 18, 2014 #1
    Weinberg-Witten theorem states that massless particles (either composite or elementary) with spin ##j > 1/2## cannot carry a Lorentz-covariant current, while massless particles with spin ##j > 1## cannot carry a Lorentz-covariant stress-energy. The theorem is usually interpreted to mean that the graviton (##j = 2##) cannot be a composite particle in a relativistic quantum field theory.

    While the argument is so strong and weird, how is it possible? Why can we not construct a theory which is massless charged vector field and therefore carry a Lorentz-covariant current ? And although we assume the second argument is right, which says massless particles with spin ##j > 1## cannot carry a Lorentz-covariant stress-energy, how does it imply that the graviton (##j = 2##) cannot be a composite particle ?
     
  2. jcsd
  3. Dec 23, 2014 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
     
  4. Dec 24, 2014 #3

    atyy

    User Avatar
    Science Advisor

    The Weinberg-Witten theorem implies that the graviton is not composite, because quantum fields usually have Lorentz-covariant stress-energy, and composite particles made from such fields will also have Lorentz-covariant stress-energy.

    There is an interesting note in the Weinberg-Witten paper that the theorem does not exclude emergent gravity approaches like Sakharov's, because there the emergence is from quantum corrections, and not from composite particles.
     
    Last edited: Dec 24, 2014
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: What does Weinberg–Witten theorem want to express?
Loading...