Circular Polarization of Primordial Gravitational Waves in String-inspired Inflationary Cosmology

Abstract

We study a mechanism to produce the circular polarization of primordial gravitational waves. The circular polarization is generated during the super-inflation driven by the Gauss-Bonnet term in the string-inspired cosmology. The instability in the tensor mode caused by the Gauss-Bonnet term and the parity violation due to the gravitational Chern-Simons term are the essential ingredients of the mechanism. We also discuss detectability of the produced circular polarization of gravitational waves. It turns out that the simple model of single-field inflation contradicts CMB observations. To circumvent this difficulty, we propose a two-field inflation model. In this two-field model, the circular polarization of gravitational waves is created in the frequency range designed by the Big-Bang Observer (BBO) or the deci-hertz gravitational-wave observatory (DECIGO).

11 pages, 7 figures, added new discussions, published version(v3), added references(v4)

References in corpus (4)

• Dark energy from modified F(R)-scalar-Gauss-Bonnet gravity
• Probing polarization states of primordial gravitational waves with CMB anisotropies
• Gauss-Bonnet cosmologies: crossing the phantom divide and the transition from matter dominance to dark energy
• Measuring a Parity Violation Signature in the Early Universe via Ground-based Laser Interferometers

Cited by in corpus (11)

• Effective Field Theory for Inflation
• Inflationary Universe with Anisotropic Hair
• Chiral Primordial Gravitational Waves from a Lifshitz Point
• Power spectra from an inflaton coupled to the Gauss-Bonnet term
• Probing polarization states of primordial gravitational waves with CMB anisotropies
• Polarization analysis of gravitational-wave backgrounds from the correlation signals of ground-based interferometers: measuring a circular-polarization mode
• Stability of Lovelock Black Holes under Tensor Perturbations
• Gravitational Radiation from Primordial Helical MHD Turbulence
• $CPT$ Violating Electrodynamics and Chern-Simons Modified Gravity
• Gauss-Bonnet Term on Vacuum Decay
• Constraining Modified Gravity with Large non-Gaussianities