# Einstein invariants

13 Dec 2017are there more invariants of the curvature than the Ricci scalar \(R\) or the invariant curvature \(R_{\mu\nu\rho\sigma}R^{\mu\nu\rho\sigma}\)? what physical interpretation would they have? is there a physical reason why the trace \(F\) of the field tensor \(F_{\mu\nu}\) is zero but \(R\) as the trace of the Ricci-tensor \(R_{\mu\nu}\) is not?