Effects of Radiation on Primordial Non-Gaussianity
  We study the non-Gaussian features in single-field slow-roll inflationary scenario where inflation is preceded by a radiation era. In such a scenario both bispectrum and trispectrum non-Gaussianities are enhanced. Interestingly, the trispectrum in this scenario does not depend up on the slow-roll parameters and thus $\tau_{NL}$ is larger than $f_{NL}$ which can be a signature of such a pre-inflationary radiation era. 
Suratna Das
astro-ph.CO gr-qc hep-ph