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Homework Help: Dirac Gamma matrices question

  1. Jul 20, 2011 #1
    1. The problem statement, all variables and given/known data

    Given that [itex]\gamma^{\mu}\gamma^{\nu}+\gamma^{\nu}\gamma^{\mu}=2g^{\mu\nu}*1[/itex] where [itex]1[/itex] is the identity matrix and the [itex]\gamma[/itex] are the gamma matrices from the Dirac equation, prove that:


    2. Relevant equations

    [itex]g^{\mu\nu}\gamma_{\nu}=\gamma^{\mu}[/itex] and [itex]g_{\mu\nu}\gamma^{\nu}=\gamma_{\mu}[/itex]

    3. The attempt at a solution

    I'm not sure what to start with. I tried expressing the terms of the relation to be proved as follows

    [itex]\gamma_{\mu}\gamma_{\nu}+\gamma_{\nu}\gamma_{\mu}=g_{\mu\alpha}\gamma^{\alpha}g_{\nu \beta}\gamma^{\beta}+ g_{\nu\beta}\gamma^{\beta}g_{\mu\alpha}\gamma^{ \alpha }[/itex]

    but that isn't going anywhere. So how do I approach this?
  2. jcsd
  3. Jul 20, 2011 #2


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    Hmm, just replace mu and nu with their possible values and see what you get. Don't forget that the metric tensor is diagonal (probably diag(+,-,-,-)).
  4. Jul 20, 2011 #3

    George Jones

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    Another way to do it is to multiply both sides of this equation by [itex]g_{\alpha \mu} g _{\beta \nu}[/itex].
  5. Jul 20, 2011 #4
    Thank you George Jones! That did the trick nicely. Using [itex]g_{\mu\alpha}g^{\alpha\nu}=\delta^{\mu}_{\nu}[/itex] the result follows easily.

    dextercioby, thank you for replying. I think your method also works but I must assume the metric is diag(1, -1 , -1, -1) which is not always the case right?
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