Exact Solutions for a Teleparallel Cosmological Model with Vector Field via Noether Symmetry

TL;DR

This paper finds exact analytical solutions in a teleparallel gravity cosmological model with a vector field, revealing different expansion behaviors including transitions from deceleration to acceleration and potential phantom phases.

Contribution

It introduces a Noether symmetry approach to derive exact solutions for a vector-torsion coupling model, analyzing special cases with distinct cosmic evolution scenarios.

Findings

For n=1, model shows transition from deceleration to acceleration, with possible phantom phase.

For n=3, model exhibits a stable acceleration phase with equation of state approaching -1.

General solutions are derived for arbitrary n, with special cases studied separately.

Abstract

We study a cosmological model in the framework of teleparallel gravity, where a vector field $A_\mu$ is non-minimally coupled to the torsion scalar $T$ in a flat Friedmann-Robertson-Walker (FRW) universe. Using the Noether symmetry approach, we identify specific forms for the coupling function $g(\xi)$ and the potential $V(\xi) = V_0 \xi^n$, with $\xi \equiv A_\mu A^\mu$. The method allows us to find exact analytical solutions for the scale factor $a(t)$ and the scalar function $\xi(t)$. General solutions for arbitrary values of $n$ are derived, but special cases such as $n = 1$ and $n = 3$ are studied separately due to their distinct behavior. For $n = 1$, the model describes a transition from decelerated to accelerated expansion, and depending on the value of the model parameter, a transition to a phantom phase is also possible, which is consistent with phantom dark energy. For the special case $n=3$, this model first experiences a deceleration phase and then enters a stable accelerating phase, such that the acceleration parameter $q(t)$ changes from positive to negative values and the equation of state parameter $\omega_\xi(t)$ tends to $-1$ at late times, similar to quintessence dark energy. Unlike the case $n=1$, in this case, no transition to the phantom phase is observed. Therefore, this model can describe the behavior of the universe during periods of dark energy dominance.