Chiral gravitational waves in Palatini-Chern-Simons gravity

• DOI: 10.1103/physrevd.107.104025
• Publication Date: 2023-05-11T14:33:02Z
• Authors: Felipe Sulantay; Macarena Lagos; Máximo Bañados
• Keywords: 500; 530

We study the parity-breaking higher-curvature gravity theory of Chern-Simons (CS), using Palatini formulation in which metric and connection are taken to be independent fields. first show that CS leads first-order derivative equations motion thus avoid typical instabilities formalism. As an initial application, we analyze cosmological propagation gravitational waves (GWs) gravity. that, due parity breaking, polarizations GWs suffer two effects during propagation: amplitude birefringence (which changes polarization ellipticity) velocity rotates plane). While is known present formalism, not gravity, but now appears fact left-handed right-handed GW have a different dispersion relation. In approximation small deviations from General Relativity (GR), do find however at least quadratically coupling parameter $\alpha$, while linearly $\alpha$. This means will most relevant effect hence this model behave similarly CS. confirm by applying current constraints on CS, showing those give tightest bounds.