Phantom Dark Ghost in Einstein-Cartan Gravity

TL;DR

This paper introduces a dark energy model using phantom dark ghost spinors interacting with torsion in Einstein-Cartan gravity, which avoids future singularities and remains stable as the universe evolves.

Contribution

It proposes a novel dark energy model with phantom spinors in Einstein-Cartan gravity that avoids singularities and maintains stability without crossing the phantom divide.

Findings

The equation of state approaches -1 from above without crossing it.

The model remains stable despite negative kinetic energy of fermions.

Torsion fields vanish as dark ghost spinors dilute over time.

Abstract

A class of dynamical dark energy models is constructed through an extended version of fermion fields corresponding to phantom dark ghost spinors, which are spin one half with mass dimension one. We find that if these spinors interact with torsion fields in a homogeneous and isotropic universe, then it does not imply any future dark energy singularity or any abrupt event, though the fermion has a negative kinetic energy. In fact, the equation of state of this dark energy model will asymptotically approach the value $w=-1$ from above without crossing the phantom divide and inducing therefore a de Sitter state. Consequently, we expect the model to be stable because no real phantom fields will be created. At late time, the torsion fields will vanish as the corresponding phantom dark ghost spinors dilute. As would be expected, intuitively, this result is unaffected by the presence of cold dark matter although the proof is not as straightforward as in general relativity.