Dissipation due to fermions in inflaton equations of motion

TL;DR

This paper investigates how fermionic decay channels affect the inflaton's equations of motion, revealing that energy loss cannot be accurately modeled by local friction terms, thus challenging common approximations in cosmology.

Contribution

It extends previous analyses of inflaton decay to fermions, demonstrating nonlocal effects and the limitations of linear response theory in this context.

Findings

Energy loss due to fermions is nonlocal and cannot be captured by simple friction terms.

The results suggest the need for more accurate, nonlocal modeling of inflaton dynamics.

Similar conclusions hold for decay into scalar particles, indicating a general issue.

Abstract

According to quantum field theory, the inflaton equation of motion does not have the local form that is generally assumed for cosmological purposes. In particular, earlier investigations of the nonequilibrium dynamics of an inflaton that decays into scalar particles suggest that the loss of inflaton energy is not well approximated by the local friction term derived from linear response theory. We extend this analysis to the case of an inflaton that decays into fermions, and reach broadly the same conclusion.