Anomalous CMB polarization and gravitational chirality

TL;DR

This paper explores how parity-violating gravity could lead to observable anomalies in CMB polarization, specifically non-zero TB and EB modes, providing a potential method to detect a gravitational wave background and its theoretical implications.

Contribution

It introduces the concept that parity-breaking gravity affects vacuum fluctuations during inflation, resulting in distinctive CMB polarization signatures that can be experimentally targeted.

Findings

Non-zero TB and EB polarization components can arise from gravitational chirality.

A TB measurement could be the most straightforward detection method for a gravitational wave background.

Theoretical implications of observing gravitational chirality are discussed.

Abstract

We consider the possibility that gravity breaks parity, with left and right handed gravitons coupling to matter with a different Newton's constant and show that this would affect their zero-point vacuum fluctuations during inflation. Should there be a cosmic background of gravity waves, the effect would translate into anomalous CMB polarization. Non-vanishing TB (and EB) polarization components emerge, revealing interesting experimental targets. Indeed if reasonable chirality is present a TB measurement would provide the easiest way to detect a gravitational wave background. We speculate on the theoretical implications of such an observation.