Polarization modes of gravitational waves in Quadratic Gravity

TL;DR

This paper investigates whether alternative gravity theories can be distinguished from general relativity through gravitational wave polarization modes, concluding that certain theories only produce tensor modes similar to GR.

Contribution

The study demonstrates that dynamical Chern-Simons and Einstein-dilaton-Gauss-Bonnet gravity cannot be differentiated from GR solely by polarization mode detection.

Findings

Only tensorial modes are detectable in these theories.

Alternative theories produce polarization modes indistinguishable from GR.

Detection of polarization modes alone cannot differentiate these theories.

Abstract

The observation of the inspiral and merger of compact binaries by the LIGO-Virgo collaboration has allowed for new tests of Einstein's theory in the extreme gravity regime, where gravitational interactions are simultaneously strong, non-linear, and dynamical. Theories beyond Einstein's can also be constrained by detecting the polarization modes of gravitational waves. In this paper, we show that dynamical Chern-Simons and Einstein-dilaton-Gauss-Bonnet gravity cannot be differentiated from general relativity based on the detection of polarization modes alone. To prove this result, we use the Newman-Penrose method and an irreducible decomposition method to find that only the tensorial modes can be detected in both these theories.