Scaling Characteristics of Hilltop and Hilltop-Squared Inflation

Abstract: One of the longstanding goals in the framework of inflation is the construction of tools that can be used to classify models in theory space. An idea that has been put forward in this context is to consider the energy dependent scaling behavior of observables to characterize different models. We implement this approach in the framework of hilltop and hilltop-squared inflation by analyzing their observables when the small-field approximation is not imposed and the energy scale $\mu$ of these models is varied as a free parameter, subject to observational constraints. We show that the scalar spectral tilt and the tensor ratio $r$ exhibit $\mu$-dependent scaling behavior and that the scaling exponents as functions of $\mu$ in turn lead to functional forms that are model dependent. Scaling relations of the type discussed here are of interest as characteristics of the inflationary theory space as well as in the context of the post-inflationary reheating process. We further observe a bifurcation behavior in the behavior of $p$-families in the spectral-tensor plane for a critical value of $\mu$.