I think the two indicies uv in the answered lagrangian means variation with respect to guv
It's in the textbook: Introducing Einstein's General Relativity "Ray d'Inverno" @haushofer
TL;DR Summary: How can I variate the quadratic Riemann curvature tensor, I tried raising and lowering the indices.
Hi,
Can you help me with this variation, I tried raising and lowering the indices.
I tried for months every possible method to reach the following answer without success.