peskin`s introduction to QFT [3.82],do not know what he had done to the underline
write out the components of each entry in the matrices
i see ,but why the \singma[\nu]\sigma[\lambta] in the first row can be write to that in the second row,
what properties of the sigma can u think of?
many thanks .it is my fault,i don`t express my question clearly,so
sigma is the 2*2 pauli matrix ,but subscript of the front two sigma matrixs in the first row is \beta ,in the second it changes to \delta,that is what i puzzled.
just write out every dirac index and massage it
get it ,there is a change which is important and very simple ,and it is until now that i realized it :
thanks a lot!
ah great, I was about to do this all for myself so that I could pin-point exactly what is going on ;)
It "always" work to write out the Dirac indices
One thing I dont like is that Peskin uses greek letter for Dirac index sometimes.. like here, very annoying and confusing
For posterity, here's a step-by-step derivation of line 1 to line 2 of eqn. 3.82 for Peskin & Schroeder QFT.
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