Polarization modes of gravitational waves in three-dimensional massive gravities

TL;DR

This paper investigates the polarization modes of gravitational waves in three-dimensional massive gravities, identifying two modes in new massive gravity and one in topologically massive gravity using the Newman-Penrose formalism.

Contribution

It applies the Newman-Penrose formalism to determine polarization modes in 3D massive gravities, providing a consistent analysis with previous metric-perturbation results.

Findings

Two polarization modes in new massive gravity

One polarization mode in topologically massive gravity

Consistent with metric-perturbation approach

Abstract

We find polarization modes of gravitational waves in topologically massive and new massive gravities by using the Newman-Penrose formalism where the null real tetrad is necessary to specify gravitational waves. The number of polarization modes is two for the new massive gravity and one for the topologically massive gravity, which is consistent with the metric-perturbation approach.