Propagation of gravitational waves in teleparallel gravity theories

TL;DR

This paper studies how gravitational waves propagate in the most general teleparallel gravity theories, showing they travel at light speed with up to six polarization modes, depending on model parameters.

Contribution

It provides a comprehensive analysis of gravitational wave modes in teleparallel gravity, extending previous work by including the most general quadratic invariants.

Findings

All modes propagate at light speed.

Up to six polarization modes can exist.

Two tensor modes are always present.

Abstract

We investigate propagation of gravitational waves in the most general teleparallel gravity model with second order field equations around the Minkowski background. We argue that in this case the most general Lagrangian at the first order of perturbations is given by the linear combination of quadratic invariants and hence coincides with the well-known new general relativity model. We derive the linearized field equations and analyze them using the principal polynomial and the Newman-Penrose formalism. We demonstrate that all gravitational wave modes propagate at the speed of light and there are up to six possible polarizations. We show that two tensorial modes of general relativity are always present and the number of extra polarizations depends on the free parameters of the new general relativity model.