In his book Gravitation and cosmology, Weinberg derives the perihelion precession of Mercury in the Robertson expansion. The final formula is(adsbygoogle = window.adsbygoogle || []).push({});

[tex]\Delta\phi =\frac{6\pi M G}{L} \frac{2+2\gamma-\beta}{3}[/tex]

The second term is one for GR (β=γ=1).

I have two questions regarding this formula:

1. The pre-factor for the second-order term of dt² in the Robertson expansion is (β-γ); the pre-factor for the dr²-term is γ. In GR, β-γ=0. So is it correct to say that the perihelion precession is due to the spatial curvature?

2. In the Newton limit (β=γ=0), the second term is 2/3, whereas Newtons theory should not predict any precession at all. Why does setting β=γ=0 not recover the Newton result?

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# A Perihelion precession in GR using Robertson expansion

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