Parity violation in framework of nonmetricity gravity

TL;DR

This paper explores how nonmetricity modified gravity could simultaneously explain cosmic birefringence and baryon asymmetry, proposing a unified framework constrained by current observational data.

Contribution

It introduces a novel interaction between nonmetricity and matter current, offering a unified explanation for polarization rotation and baryon asymmetry in the early universe.

Findings

The model can account for both cosmic birefringence and baryon asymmetry.

Constraints on model parameters are derived from observational data.

Minimal coupling of nonmetricity scalar and matter current is less favored.

Abstract

The latest observational data of Planck satellite shows nontrivial value of polarization rotation angle caused by cosmic birefringence in the early universe. Moreover, the asymmetry of baryons versus anti-baryons still remains mysterious. Both of them indicates that there should be hidden new physics such as fundamental symmetry breaking. In this paper, we try to interpret these two events in framework of nonmetricity modified gravity. We introduce an interaction term between nonmetricity-based function and matter current, and calculate both the rotation angle and baryon-to-photon ratio. We also constrain the model parameters using the current observational data. With some specific examples, we demonstrate that in nonmetricity gravity theory, these two events can be interpreted in a unified way. Nevertheless, the minimal coupling of nonmetricity scalar and the matter current might not be favored.