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Propagator for matrix fields (based on Srednicki ch80, p490)

  1. Nov 16, 2011 #1

    If I have a matrix valued field [itex] B(x)_i^{..j}=B^a (x) (T^a)_i^{..j} [/itex] and the relevant part of my Lagrangian is [itex]L=Tr(-\tfrac{1}{2}\partial^{\mu}B\partial_{\mu}B+..) [/itex] then how can I see that the propagator for the matrix field is [itex] \Delta_{i..k}^{..j..l}(k^2)=\tfrac{(T^a)_i^j(T^a)_k^l}{k^2-i\epsilon} [/itex] ?

    I understand that if we expand the L in terms of the coefficent field we get [itex] L=-\tfrac{1}{2}\partial^{\mu}B^a\partial_{\mu}B^{a} [/itex] and this leads to the propagator for the coefficient field as [itex] \Delta^{ab}(k^2)=\tfrac{\delta^{ab}}{k^2-i\epsilon} [/itex], (just like usual for a massless scalar field) but not sure how to see the propagator of matrix field...

    thanks for any help...
  2. jcsd
  3. Nov 18, 2011 #2
    Also why exactly does each external propagator carry at [itex] T^{a_i} [/itex] factor?
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