- #1
intervoxel
- 195
- 1
I'm confused about index calculation in eq. 8.25, Mandl QFT textbook. Can anyone give me a detailed explanation showing the equality below?
[itex]X=\frac{1}{2}A_{\delta \alpha}^+(\bf{p'})\Gamma_{\alpha \beta}(\bf{p'})A_{\beta \gamma}^+(\bf{p})\widetilde{\Gamma}_{\gamma\delta}[/itex]
[itex]=\frac{1}{2}Tr[A^+(\bf{p'})\Gamma A^+(\bf{p})][/itex]
Please be patient, I'm learning index notation from scratch.
Thanks.
[itex]X=\frac{1}{2}A_{\delta \alpha}^+(\bf{p'})\Gamma_{\alpha \beta}(\bf{p'})A_{\beta \gamma}^+(\bf{p})\widetilde{\Gamma}_{\gamma\delta}[/itex]
[itex]=\frac{1}{2}Tr[A^+(\bf{p'})\Gamma A^+(\bf{p})][/itex]
Please be patient, I'm learning index notation from scratch.
Thanks.