Upper Bounds on the Mass of Fundamental Fields from Primordial Universe

TL;DR

This paper derives upper bounds on the masses of fundamental fields during inflation by analyzing vacuum zero point energy fluctuations and their impact on primordial perturbations, ensuring consistency with observed Gaussianity and tensor-to-scalar ratio constraints.

Contribution

It introduces a method to constrain fundamental field masses during inflation based on vacuum fluctuation effects and non-Gaussianity limits, considering mass hierarchies.

Findings

Combined mass scale of fields must be below 10^{14} GeV.

Vacuum zero point fluctuations induce large non-Gaussianities if masses are too high.

Heaviest field's mass may be unconstrained if isolated.

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.