# Parity-Violating Gravity and GW170817 in Non-Riemannian Cosmology

## TL;DR

This paper investigates how parity-violating extensions of non-Riemannian gravity affect gravitational wave propagation, revealing potential signatures that distinguish polarization states and constraining parameters using GW170817 data.

## Contribution

It introduces a non-Riemannian teleparallel framework for parity-violating gravity and analyzes its impact on gravitational wave signatures, extending beyond metric-based theories.

## Key findings

- Parity-violating terms cause polarization-dependent gravitational wave signatures.
- Propagation speed of GWs is scale-dependent and can differ from light speed.
- Constraints on model parameters are derived from GW170817 observations.

## Abstract

The cosmological propagation of tensor perturbations is studied in the context of parity-violating extensions of the symmetric teleparallel equivalent of General Relativity theory. This non-Riemannian formulation allows for a wider variety of consistent extensions than the metric formulation of gravity theory. It is found that while many of the possible quadratic terms do not influence the propagation of the gravitational waves, a generic modification predicts a signature that distinguishes the left- and right-handed circular polarizations. The parameters of such modifications can be constrained stringently because the propagation speed of the gravitational waves is scale-dependent and differs from the speed of light.