Gauss-Bonnet dark energy

TL;DR

This paper introduces a Gauss-Bonnet dark energy model inspired by string theory, showing it can produce late-time acceleration, transient phantom phases, and potentially prevent Big Rip scenarios.

Contribution

It presents a novel scalar-Gauss-Bonnet coupling model that explains late universe acceleration and avoids future singularities, inspired by string/M-theory.

Findings

Effective phantom or quintessence phases can occur due to the coupling.

The Gauss-Bonnet term can dominate at high curvature, making phantom phases transient.

Scalar-Gauss-Bonnet coupling can prevent Big Rip in phantom cosmology.

Abstract

We propose the Gauss-Bonnet dark energy model inspired by string/M-theory where standard gravity with scalar contains additional scalar-dependent coupling with Gauss-Bonnet invariant. It is demonstrated that effective phantom (or quintessence) phase of late universe may occur in the presence of such term when the scalar is phantom or for non-zero potential (for canonical scalar). However, with the increase of the curvature the GB term may become dominant so that phantom phase is transient and $w=-1$ barrier may be passed. Hence, the current acceleration of the universe may be caused by mixture of scalar phantom and (or) potential/stringy effects. It is remarkable that scalar-Gauss-Bonnet coupling acts against the Big Rip occurence in phantom cosmology.