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

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
1 reply · 2K views
LAHLH
Messages
405
Reaction score
2
Hi,

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 coefficient 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...
 
Physics news on Phys.org
Also why exactly does each external propagator carry at [itex]T^{a_i}[/itex] factor?