Cosmological Perturbations of Extended NGR Model with Parity Violation

TL;DR

This paper explores an extended New General Relativity model with parity violation, analyzing its cosmological perturbations and demonstrating conditions under which it avoids ghost instabilities, thus contributing to modified gravity theories.

Contribution

It introduces a parity-odd quadratic torsion term into the NGR model and studies its cosmological perturbations, highlighting stability conditions not previously examined.

Findings

The extended NGR model can avoid ghost instabilities in specific parameter regions.

The parity-odd term influences the stability of cosmological perturbations.

Certain parameter choices ensure the model remains ghost-free.

Abstract

Recently the modified teleparallel gravity models attracted a lot of interests. In this paper we consider more extensions to the New General Relativity (NGR) model with parity violations. This extended NGR model differs from the normal NGR model by the inclusion of additional parity-odd term that is quadratic in the torsion tensor. By investigating its cosmological perturbations of this model, we find that this model can avoid ghost instabilities in certain regions of the parameter space, where the coefficient of the parity-odd term does not vanish.