A comment on trans-Planckian physics in inflationary universe

TL;DR

This paper highlights that models modifying the primordial density perturbation spectrum due to trans-Planckian physics must account for significant back reaction effects from inflaton fluctuations, which have been previously overlooked.

Contribution

It emphasizes the importance of considering back reaction effects of inflaton fluctuations in models involving trans-Planckian physics during inflation.

Findings

Inflaton fluctuation energy density becomes significantly large.

Back reaction effects cannot be neglected in such models.

Previous studies overlooked this critical aspect.

Abstract

There are several works searching for a clue of trans-Planckian physics on the primordial density perturbation spectrum. Here we would like to point out an important aspect which has been overlooked so far. When we consider a model in which the primordial density perturbation spectrum is modified due to trans-Planckian physics, the energy density of fluctuations of the inflaton field necessarily becomes significantly large, and hence its back reaction to the cosmic expansion rate cannot be neglected.