Interacting Quintessence in a New Scalar-Torsion Gravity

TL;DR

This paper explores a scalar-torsion gravity model within teleparallel gravity, revealing stable scaling solutions that could address the cosmological coincidence problem without fine-tuning.

Contribution

It introduces a non-minimal derivative coupling between a scalar field and vector torsion, analyzing its phase-space dynamics and stability, especially with dark sector interactions.

Findings

No scaling attractors in non-interacting case.

Scaling attractors emerge with dark matter-dark energy interaction.

Potential alleviation of the coincidence problem.

Abstract

In the framework of teleparallel equivalent of general relativity, we study a gravity theory where a scalar field beyond its minimal coupling, is also coupled with the vector torsion through a non-minimal derivative coupling. After a suitable choice of auxiliary variables that allows us to perform the phase-space analysis of the model we obtain the critical points and their stability. While there is no scaling attractor in non-interacting scenario, by considering an interaction between dark energy and dark matter, we find scaling attractors in which the fractional densities of dark energy and matter are non-vanishing constants over there. The universe can evolve to these scaling attractors regardless of initial conditions and the cosmological coincidence problem could be alleviated without fine-tunings.