Polarization of gravitational waves in general teleparallel theories of gravity

TL;DR

This paper investigates the polarization modes of gravitational waves in teleparallel gravity theories, revealing a variety of possible polarization states depending on the theory parameters, some matching those of general relativity.

Contribution

It classifies gravitational wave polarizations in teleparallel theories using Newman-Penrose formalism, identifying multiple polarization classes and their relation to general relativity.

Findings

Multiple polarization classes identified, including two to six polarizations.

Some teleparallel theories share polarization features with general relativity.

The polarization depends on the specific parameters of the theory.

Abstract

We determine the possible gravitational wave polarizations in two general classes of teleparallel gravity theories, using the metric and symmetric teleparallel geometries. For this purpose we apply the Newman-Penrose formalism, and find that depending on the choice of parameters, the $\mathrm{E}(2)$ class of the theories is one of $\mathrm{N}_2, \mathrm{N}_3, \mathrm{III}_5, \mathrm{II}_6$, corresponding to two to six polarizations, where all of them include the two tensor polarizations known from general relativity. We also find classes of theories apart from general relativity which yield the same polarizations.