Upper Bounds on the Mass of Fundamental Fields from Primordial Universe

Abstract: We study the fluctuations in the vacuum zero point energy associated to quantum fields and their statistical distributions during inflation. It is shown that the perturbations in the vacuum zero point energy have large amplitudes which are highly non-Gaussian. The effects of vacuum zero point fluctuations can be interpreted as the loop corrections in primordial power spectrum and bispectrum. Requiring that the primordial curvature perturbation to remain nearly Gaussian and the loop corrections to be under perturbative control impose strong upper bounds on the mass of fundamental fields during inflation. These bounds depend on the hierarchy of the masses in the theory such as whether or not the masses are at the similar orders. While the mass of the heaviest field in the hierarchy may not be constrained but it is shown that a combination of the masses of the fields can not be much heavier than the Hubble scale during inflation, otherwise their vacuum zero point fluctuations induce large non-Gaussianities in primordial perturbations. Considering the observational upper bound on tensor to scalar ratio, we conclude that this combined mass scale is lighter than $10^{14}$ GeV.