Dynamical Relaxation of Dark Energy: A Solution to Early Inflation, Late-time Acceleration and the Cosmological Constant Problem

TL;DR

This paper proposes a modified gravity model with a Gauss-Bonnet term and a scalar field that dynamically relaxes dark energy, explaining early inflation, late-time acceleration, and addressing the cosmological constant problem.

Contribution

It introduces a string theory-inspired model that naturally relaxes vacuum energy and predicts a small deviation from a cosmological constant.

Findings

Dynamical relaxation of vacuum energy to near zero.

Provides a unified explanation for inflation and late-time acceleration.

Predicts a slight deviation from w=-1 in dark energy.

Abstract

In recent years different explanations are provided for both an inflation and a recent acceleration in the expansion of the universe. In this Letter we show that a model of physical interest is the modification of general relativity with a Gauss-Bonnet term coupled to a dynamical scalar-field as predicted by certain versions of string theory. This construction provides a model of evolving dark energy that naturally explains a dynamical relaxation of the vacuum energy (gravitationally repulsive potential) to a small value (exponentially close to zero) after a sufficient number of e-folds. The model also leads to a small deviation from the $w=-1$ prediction of non-evolving dark energy.