Poincar\'e Gauge Theory With Coupled Even And Odd Parity Dynamic Spin-0 Modes: Dynamic Equations For Isotropic Bianchi Cosmologies

TL;DR

This paper explores a novel Poincaré gauge gravity model with coupled spin-0 modes in isotropic cosmologies, deriving equations and demonstrating observable effects of parity coupling through numerical simulations.

Contribution

It introduces a new gravity model with coupled parity modes and derives the corresponding dynamical equations for isotropic Bianchi cosmologies.

Findings

Effective Lagrangian and Hamiltonian derived for the model

First order dynamical equations compatible with FLRW models

Numerical simulations show effects of parity coupling

Abstract

We are investigating the dynamics of a new Poincar\'e gauge theory of gravity model, which has cross coupling between the spin-0$^+$ and spin-0$^-$ modes. To this end we here consider a very appropriate situation---homogeneous-isotropic cosmologies---which is relatively simple, and yet all the modes have non-trivial dynamics which reveals physically interesting and possibly observable results. More specifically we consider manifestly isotropic Bianchi class A cosmologies; for this case we find an effective Lagrangian and Hamiltonian for the dynamical system. The Lagrange equations for these models lead to a set of first order equations that are compatible with those found for the FLRW models and provide a foundation for further investigations. Typical numerical evolution of these equations shows the expected effects of the cross parity coupling.