Poincar\'e gauge theory with even and odd parity dynamic connection modes: isotropic Bianchi cosmological models

TL;DR

This paper explores an extended Poincaré gauge theory of gravity with even and odd parity modes, analyzing isotropic Bianchi cosmological models to understand their dynamics and potential observable effects.

Contribution

It introduces a model with both 0+ and 0- parity modes in Poincaré gauge gravity and studies its dynamics in isotropic cosmologies.

Findings

Oscillations of the 0+ mode can mimic accelerated expansion.

Extended model includes cross parity couplings.

Dynamical equations and evolution patterns are derived.

Abstract

The Poincar\'e gauge theory of gravity has a metric compatible connection with independent dynamics that is reflected in the torsion and curvature. The theory allows two good propagating spin-0 modes. Dynamical investigations using a simple expanding cosmological model found that the oscillation of the 0$^+$ mode could account for an accelerating expansion similar to that presently observed. The model has been extended to include a $0^{-}$ mode and more recently cross parity couplings. We investigate the dynamics of this model in a situation which is simple, non-trivial, and yet may give physically interesting results that might be observable. We consider homogeneous cosmologies, more specifically, isotropic Bianchi class A models. We find an effective Lagrangian for our dynamical system, a system of first order equations, and present some typical dynamical evolution.