Linear perturbations of Kerr black hole in quadratic gravity

Employing the Newman-Penrose formalism and following the classic Teukolsky-like approach, we linearize the field equations of quadratic gravity on the Kerr background and combine them with the linearized Ricci and Bianchi identities. This leads to constraints on linear perturbations of the Kerr spacetime in quadratic gravity. The resulting differential equations are decoupled in such a way that only the Ricci tensor perturbations need to be found on the Kerr background in order to fully determine the solution. The results are illustrated in the simple nontrivial cases of the Schwarzschild and Minkowski geometries.