Bridging inflation and reheating: chiral gravitational waves from aHz to GHz

TL;DR

This paper explores how parity-violating interactions during inflation and reheating can produce detectable chiral gravitational waves across a wide frequency spectrum, offering new insights into early Universe physics.

Contribution

It introduces a model linking inflation and reheating through a parity-violating term, predicting observable chiral GWs from CMB to GHz frequencies, and constrains early Universe parameters.

Findings

Chiral GWs induce detectable CMB polarization correlations.

Reheating produces fully circularly polarized GWs with enhanced amplitudes.

Constraints on PV energy scale and inflationary potential from GW backreaction.

Abstract

In this paper, we investigate chiral gravitational wave (GW) signals generated from inflation to reheating, driven by a parity-violating (PV) term coupled to the inflaton. During inflation, the PV term reduces the sound horizon for right-handed circularly polarized GWs, and amplifies their power spectra relative to left-handed GWs. At CMB scales, these chiral GWs induce BB as well as non-vanishing EB and TB correlations in CMB, which are potentially detectable by LiteBIRD. During reheating, subhorizon modes undergo tachyonic instability, leading to fully circularly polarized GWs with enhanced amplitudes, detectable through the resonant cavity experiment. The absence of backreaction effect of enhanced chiral GWs imposes constraints on the energy scale of the PV term, the inflationary potential, and the reheating history. Our findings highlight the potential of multi-frequency GW experiments to offer a unique probe of the parity violation and early Universe.