# Gamma matrix identity (QFT)

1. Sep 7, 2013

### Catria

1. The problem statement, all variables and given/known data

Prove that $\gamma^{a}\gamma^{b}\gamma^{c}\gamma^{d}\gamma^{e}\gamma_{a}$ = $2\left(\gamma^{e}\gamma^{b}\gamma^{c}\gamma^{d}+\gamma^{d}\gamma^{c} \gamma^{b}\gamma^{e}\right)$

Each of the $\gamma^{i}$s are as used in the Dirac equation.

2. Relevant equations

$\gamma^{a}\gamma^{b}\gamma^{c}\gamma^{d}\gamma_{a}$ = $-2\gamma^{d}\gamma^{c}\gamma^{b}$

$\gamma^{a}\gamma^{b} + \gamma^{b}\gamma^{a} = 2g^{ab}$

3. The attempt at a solution

$\gamma^{a}\gamma^{b}\gamma^{c}\gamma^{d}\gamma^{e}\gamma_{a}$ = $2g^{ab}\gamma^{c}\gamma^{d}\gamma^{e}\gamma_{a}$ - $\gamma^{b}\gamma^{a}\gamma^{c}\gamma^{d}\gamma^{e}\gamma_{a}$

= $2\gamma^{c}\gamma^{d}\gamma^{e}\gamma^{b}$ + $2\gamma^{b}\gamma^{e}\gamma^{d}\gamma^{c}$

Perhaps I mixed up something or there is a typo...

2. Sep 7, 2013

### TSny

I think what you wrote so far is correct. But, as you can see, it is not yet very close to what you want.

Instead, start over and try commuting $\gamma^{e}$ with $\gamma_{a}$. To do this, you will need to use the identity obtained by lowering $a$ in the identity $\gamma^{a}\gamma^{b} + \gamma^{b}\gamma^{a} = 2g^{ab}$

3. Sep 7, 2013

Thank you.