New shape for cross-bispectra in Chern-Simons gravity

TL;DR

This paper explores how non-standard initial conditions during inflation can enhance parity-violating non-Gaussianity in Chern-Simons gravity, providing new observational constraints despite previous ghost issues.

Contribution

It introduces a novel approach of deviating from Bunch-Davies initial conditions to amplify parity-violating signals in the scalar-tensor cross-bispectra within Chern-Simons gravity.

Findings

Enhanced parity-violating non-Gaussianity in flattened configurations.

Potential to constrain parity-violating gravity through new bispectrum signatures.

Demonstrates that initial condition deviations can overcome ghost suppression effects.

Abstract

Chern-Simons gravity is known to suffer from graviton ghost production during inflation, which suppresses the parity-violating power spectrum at scales relevant to cosmic microwave background observations. In this work, we show that allowing the initial conditions of inflation to deviate from the standard Bunch-Davies state can enhance parity-violating non-Gaussianity in the scalar-tensor cross-bispectra. Our results reveal a significant additional contribution to the cross-bispectra in the flattened configuration, offering a new avenue to constrain parity-violating gravity.