Trapping effects on inflation

TL;DR

This paper develops a Lagrangian influence functional approach to derive a Langevin equation for the inflaton, accounting for trapping points, and analyzes the resulting noise and dissipation effects on inflationary fluctuations.

Contribution

It introduces a self-consistent Langevin equation with fluctuation-dissipation relation for trapping effects during inflation, including colored noise and dissipation in strong coupling regimes.

Findings

Power spectrum of inflaton fluctuations is computed for single trapping points.

The power spectrum becomes blue when multiple trapping points are closely spaced.

Dissipation effects may influence trapping dynamics in inflation.

Abstract

We develop a Lagrangian approach based on the influence functional method so as to derive self-consistently the Langevin equation for the inflaton field in the presence of trapping points along the inflaton trajectory. The Langevin equation exhibits the backreaction and the fluctuation-dissipation relation of the trapping. The fluctuation is induced by a multiplicative colored noise that can be identified as the the particle number density fluctuations and the dissipation is a new effect that may play a role in the trapping with a strong coupling. In the weak coupling regime, we calculate the power spectrum of the noise-driven inflaton fluctuations for a single trapping point and studied its variation with the trapping location. We also consider a case with closely spaced trapping points and find that the resulting power spectrum is blue.