Non-Gaussianity as a signature of thermal initial condition of inflation

Understand

We study non-Gaussianities in the primordial perturbations in single field inflation where there is radiation era prior to inflation.

• Inflation takes place when the energy density of radiation drops below the value of the potential of a coherent scalar field.
• We compute the thermal average of the two, three and four point correlation functions of inflaton fluctuations.
• The three point function is proportional to the slow roll parameters and there is an amplification in $f_{NL}$ by a factor of 65 to 90 due to the contribution of the thermal bath, and we conclude that the bispectrum is in the range of detectability with the 21-cm anisotropy measurements.