Linear cosmological perturbations in almost scale-invariant fourth-order gravity

Jorge L. Fuentes, Usman A. Gillani, Karim A. Malik

We study a class of almost scale-invariant modified gravity theories, using a particular form of $f(R,G)=\alpha R^2+\beta G\log G$ where $R$ and $G$ are the Ricci and Gauss-Bonnet scala…