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since g^{μν}g_{μν}= 4 where g = diag[1,-1,-1,-1], see:

https://www.physicsforums.com/threads/questions-about-tensors-in-gr.39158/

Is the following equation correct?

x^{μ}x_{μ}= g^{μν}x_{ν}g_{μν}x^{ν}= g^{μν}g_{μν}x^{ν}x_{ν}= 4 x^{μ}x_{μ}

If not, where is the problem?

Cheers,

Adam

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# Metric tensor

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