Parity-Odd and Even Trispectrum from Axion Inflation

Understand

The four-point correlation function of primordial scalar perturbations has parity-even and parity-odd contributions and the parity-odd signal in cosmological observations is opening a novel window to look for new physics in the inflationary epoch.

• We study the distinct parity-odd and even prediction from the axion inflation model, in which the inflaton couples to a vector field via a Chern-Simons interaction, and the vector field is considered to be either approximately massless ($m_A \ll $ Hubble scale $H$) or very massive ($m_A \sim H $).
• The parity-odd signal arises due to one transverse mode of the vector field being predominantly produced during inflation.
• We adopt the in-in formalism to evaluate the correlation functions.