Chiral Primordial Gravitational Waves from a Lifshitz Point

TL;DR

This paper predicts that quantum gravity at a Lifshitz point during inflation produces circularly polarized primordial gravitational waves, a testable signature of parity violation in the early universe.

Contribution

It demonstrates that primordial gravitational waves are inherently chiral in Hořava-Lifshitz quantum gravity, linking quantum gravity theory to observable cosmological phenomena.

Findings

Primordial gravitational waves are predicted to be circularly polarized.

Chirality is a robust feature of quantum gravity at a Lifshitz point.

Potential observational tests include cosmic microwave background and gravitational wave detectors.

Abstract

We study primordial gravitational waves produced during inflation in quantum gravity at a Lifshitz point proposed by Ho${\rm\check{r}}$ava. Assuming power-counting renormalizability, foliation preserving diffeomorphism invariance, and the condition of detailed balance, we show that primordial gravitational waves are circularly polarized due to parity violation. The chirality of primordial gravitational waves is a quite robust prediction of quantum gravity at a Lifshitz point which can be tested through observations of cosmic microwave background radiation and stochastic gravitational waves.