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Kinetic Terms

  1. Jan 30, 2008 #1
    I've been wondering about terms you typically find in the action of a field theory, for example consider the kinetic term of a scalar field

    [tex]S=\int d^4x(\partial_\mu\phi\partial^\mu\phi).[/tex]

    I've read that it can be thought of as the kinetic energy of the field - but this just doesn't sit to well with me for some reason. I mean the kinetic energy of a massless field seems strange.

    Can anyone here provide any deeper insights into this?
  2. jcsd
  3. Jan 31, 2008 #2


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    does a photon has kinetic energy?
  4. Jan 31, 2008 #3
    mjsd is right

    think the defintion (classically also) of what K is???

    roughly speaking is the amount of energy that a system has, due just to his movement.

    massles particles do move always at c.
  5. Jan 31, 2008 #4
    hmmm... well I know that a photon has energy [tex]E=h\nu[/tex], but I've never called it knietic energy - but I see what you are getting at.
  6. Feb 1, 2008 #5
    rember also that for m=0 E=pc
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