Scaling attractors in interacting teleparallel dark energy

TL;DR

This paper demonstrates that by allowing a dynamic non-minimal coupling in teleparallel dark energy models, scaling attractors can exist, potentially solving the cosmological coincidence problem without fine-tuning.

Contribution

It introduces a model with a dynamically changing coupling coefficient, showing the existence of scaling attractors in teleparallel dark energy, which was not previously found.

Findings

Scaling attractors exist with dynamic coupling.

The universe can reach these attractors regardless of initial conditions.

Potential alleviation of the cosmological coincidence problem.

Abstract

It has been proposed recently the existence of a non-minimal coupling between a canonical scalar field (quintessence) and gravity in the framework of teleparallel gravity, motivated by similar constructions in the context of General Relativity. The dynamics of the model, known as teleparallel dark energy, has been further developed, but no scaling attractor has been found. Here we consider a model in which the non-minimal coupling is ruled by a dynamically changing coefficient $\alpha\equiv f_{,\phi}/\sqrt{f}$, with $f(\phi)$ an arbitrary function of the scalar field $\phi$. It is shown that in this case the existence of scaling attractors is possible, which means that the universe will eventually enter these scaling attractors, regardless of the initial conditions. As a consequence, the cosmological coincidence problem could be alleviated without fine-tunings.