- #1
da_willem
- 599
- 1
I'm reading in on the subject of General Relativity and came across a few things I don't understand. First of all I'm not sure where the following rule comes from, and maybe someone can explain or derive it for me:
[tex] \eta^{\mu \beta} h_{\nu \sigma,\beta} = h_{\nu \sigma}^{,\mu} [/tex]
And I also found the following things about the metric tensor I don't understand:
[tex] g^\mu_\mu = g_{\mu \nu}g^{\mu \nu} = 4[/tex]
[tex] \eta^{\mu \beta} h_{\nu \sigma,\beta} = h_{\nu \sigma}^{,\mu} [/tex]
And I also found the following things about the metric tensor I don't understand:
[tex] g^\mu_\mu = g_{\mu \nu}g^{\mu \nu} = 4[/tex]