- #1
center o bass
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Hi I'm trying to figure out the proof of why the gamma matrices are traceless. I found a proof at wikipedia under 'trace identities' here
http://en.wikipedia.org/wiki/Gamma_matrices
(it's the 0'th identity)
and from the clifford algebra relation
[tex] \{\gamma^\mu, \gamma^\nu\} = 2\eta^{\mu \nu}[/tex]
one get that
[tex] \frac{\gamma^\mu \gamma^\mu}{\eta^{\mu \mu}} = I[/tex]
thus
[tex] Tr(\gamma^\nu) = \frac{1}{\eta^{\mu \mu}} Tr(\gamma^\nu \gamma^\mu \gamma^\mu) = \frac{1}{\eta^{\mu \mu}} Tr(\{\gamma^\nu, \gamma^\mu\} \gamma^\mu - \gamma^\mu \gamma^\nu \gamma^\mu)[/tex]
and here it seems like they set
[tex]\frac{1}{\eta^{\mu \mu}} Tr(\{\gamma^\nu, \gamma^\mu\} \gamma^\mu) = \frac{1}{\eta^{\mu \mu}} Tr(2 \eta^{\nu \mu} \gamma^\mu ) = 0.[/tex]
But why is this true?
http://en.wikipedia.org/wiki/Gamma_matrices
(it's the 0'th identity)
and from the clifford algebra relation
[tex] \{\gamma^\mu, \gamma^\nu\} = 2\eta^{\mu \nu}[/tex]
one get that
[tex] \frac{\gamma^\mu \gamma^\mu}{\eta^{\mu \mu}} = I[/tex]
thus
[tex] Tr(\gamma^\nu) = \frac{1}{\eta^{\mu \mu}} Tr(\gamma^\nu \gamma^\mu \gamma^\mu) = \frac{1}{\eta^{\mu \mu}} Tr(\{\gamma^\nu, \gamma^\mu\} \gamma^\mu - \gamma^\mu \gamma^\nu \gamma^\mu)[/tex]
and here it seems like they set
[tex]\frac{1}{\eta^{\mu \mu}} Tr(\{\gamma^\nu, \gamma^\mu\} \gamma^\mu) = \frac{1}{\eta^{\mu \mu}} Tr(2 \eta^{\nu \mu} \gamma^\mu ) = 0.[/tex]
But why is this true?
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