Extracting Tensor Algebra Term with SU(N) Generators and Numbers

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SUMMARY

The discussion centers on extracting the term Tr(φcφd[Ta,Tc][Tb,Td])AaμAbμ from the expression (Taμφa + Aμaφb[Ta,Tb] + Aμaφb[Ta,Tb])2. Participants suggest that squaring the third term is necessary but express confusion over obtaining a trace. They seek references that clarify the trace operation, particularly in relation to the standard choice Tr(tatb) ~ δab.

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  • Understanding of SU(N) Lie algebra and its generators
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spaghetti3451
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Consider the expression

$$\left(T^{a}\partial_{\mu}\varphi^{a} + A_{\mu}^{a}\varphi^{b}[T^{a},T^{b}] + A_{\mu}^{a}\phi^{b}[T^{a},T^{b}]\right)^{2},$$

where ##T^{a}## are generators of the ##\textbf{su}(N)## Lie algebra, and ##\varphi^{a}##, ##\phi^{a}## and ##A_{\mu}^{a}## are numbers.

How can I extract the term ##\text{Tr}(\phi^{c}\phi^{d}[T^{a},T^{c}][T^{b},T^{d}])A^{a}_{\mu}A^{b\mu}## from this expression?I suppose you have to square the third term, but I do not get a trace!
 
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I don't get a trace either. Can you give some references where the trace is written? Maybe they use the standard choice trace(t_a t_b)~ delta_{ab} or some similar rewriting.
 

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