Scale Invariant Dark Energy

TL;DR

This paper explores a scale-invariant dark energy model with a scalar field and small R^2 modifications, analyzing its cosmological evolution and comparing it with standard models, including effects of scalar field production.

Contribution

It introduces a novel scale-invariant dark energy model with R^2 corrections and provides analytical solutions for its cosmological behavior.

Findings

R^2 term significantly alters cosmological evolution

Analytical solutions exhibit transplanckian oscillations

Scalar field production impacts cosmological dynamics

Abstract

A global scale-invariant Dark Energy model based on Induced Gravity with the addition of a small $R^2$ contribution is examined. The scalar field (quintessence), playing the role of Dark Energy, has a quartic potential and generates Newton's constant with its non-minimal coupling (after introducing a suitable symmetry breaking). Even when small, the $R^2$ contribution significantly modifies the cosmological evolution of the matter-gravity system. The solutions to this model are obtained analytically through a perturbative expansion and oscillate with transplanckian frequency. They are then compared with similar solutions found for $\Lambda$CDM cosmology plus $R^2$. Finally scalar field production is perturbatively taken into account in a simple model and the resulting effects illustrated.