Linearized Riemann curvature operator (source code)

= Linearized Riemann curvature operator

The linearized Riemann tensor defines an operator on two-forms by
$$
(\mathcal R\omega)_{ab}=\frac12R^{(1)}_{ab}{}^{cd}\omega_{cd}.
$$
Unlike the metric perturbation itself, this operator is invariant under linearized gauge transformations.