# Loop corrections to primordial fluctuations from inflationary phase transitions

## TL;DR

This paper studies how loop corrections from spectator fields during inflation, especially during phase transitions, can significantly affect primordial curvature fluctuations, with suppressed effects on tensor modes.

## Contribution

It introduces a detailed analysis of loop corrections from spectator fields during inflationary phase transitions, highlighting the dominant decay channel affecting curvature perturbations.

## Key findings

- Loop corrections can significantly modify curvature perturbations.
- Tensor perturbation corrections are suppressed by spatial derivatives.
- Decay of spectator fields into curvature perturbations depends on field masses near the Hubble scale.

## Abstract

We investigate loop corrections to the primordial fluctuations in the single-field inflationary paradigm from spectator fields that experience a smooth transition of their vacuum expectation values. We show that when the phase transition involves a classical evolution effectively driven by a negative mass term from the potential, important corrections to the curvature perturbation can be generated by field perturbations that are frozen outside the horizon by the time of the phase transition, yet the correction to tensor perturbation is naturally suppressed by the spatial derivative couplings between spectator fields and graviton. At one-loop level, the dominant channel for the production of primordial fluctuations comes from a pair-scattering of free spectator fields that decay into the curvature perturbations, and this decay process is only sensitive to field masses comparable to the Hubble scale of inflation.