Equation of state for dark energy in $f(T)$ gravity

TL;DR

This paper investigates the evolution of dark energy's equation of state in various $f(T)$ gravity models, showing that combined models can cross the phantom divide line, aligning with recent observational data.

Contribution

It demonstrates that combined $f(T)$ models can realize the crossing of the phantom divide, a feature not possible in individual exponential or logarithmic $f(T)$ models.

Findings

Crossing of $w_{DE} = -1$ is possible in combined $f(T)$ models.

The crossing occurs from above to below -1, opposite to $f(R)$ models.

The model's predictions are consistent with recent observational data.

Abstract

We study the cosmological evolutions of the equation of state for dark energy $w_{\mathrm{DE}}$ in the exponential and logarithmic as well as their combination $f(T)$ theories. We show that the crossing of the phantom divide line of $w_{\mathrm{DE}} = -1$ can be realized in the combined $f(T)$ theory even though it cannot be in the exponential or logarithmic $f(T)$ theory. In particular, the crossing is from $w_{\mathrm{DE}} > -1$ to $w_{\mathrm{DE}} < -1$, in the opposite manner from $f(R)$ gravity models. We also demonstrate that this feature is favored by the recent observational data.