STABILITY OF INFLATION IN 4TH ORDER GRAVITY

A perturbative scheme to analyze the evolution of perturbations in fourth order gravity theory is developed. The scheme is applied to study both scalar field and metric perturbations, taking backreaction into account. It is shown that short wavelength gravitational perturbations decay rapidly, lose information about their initial conditions and are affected for long times primarily by the scalr field perturbations. The scalar field perturbations remain essentially constant after a short decay. For reasonable initial conditions inflation will proceed virtually unimpeded. © 1990.