A New Exponential Gravity

Abstract

We propose a new exponential f(R) gravity model with f(R) = (R − λc) e λ(c/R)n and n > 3, λ ≥ 1, c > 0 to explain late-time acceleration of the universe. At the high curvature region, the model behaves like the Λ CDM model. In the asymptotic future, it reaches a stable de-Sitter spacetime. It is a cosmologically viable model and can evade the local gravity constraints easily. This model shares many features with other f(R) dark energy models like Hu-Sawicki model and Exponential gravity model. In it the dark energy equation of state is of an oscillating form and can cross phantom divide line ωde = −1. In particular, in the parameter range 3 < n ≤ 4, λ ∼ 1, the model is most distinguishable from other models. For instance, when n = 4, λ = 1, the dark energy equation of state will cross −1 in the earlier future and has a stronger oscillating form than the other models, the dark energy density in asymptotical future is smaller than the one in the high curvature region. This new model can evade the local gravity tests easily when n > 3 and λ > 1.