Bubble nucleation and inflationary perturbations

TL;DR

This paper investigates how bubble nucleation during inflation can leave anisotropic and scale-dependent imprints on primordial perturbations, affecting the CMB power spectrum and providing potential observational signatures.

Contribution

It introduces a model where bubble nucleation influences inflationary perturbations, analyzing the resulting anisotropic and scale-dependent corrections to the CMB.

Findings

Bubble nucleation induces anisotropic corrections in the curvature perturbation.

Scale-dependent effects are imprinted on the CMB power spectrum.

Observable signatures depend on the bubble's expansion and collision timing.

Abstract

In this work we study the imprints of bubble nucleation on primordial inflationary perturbations. We assume that the bubble is formed via the tunneling of a spectator field from the false vacuum of its potential to its true vacuum. We consider the configuration in which the observable CMB sphere is initially outside of the bubble. As the bubble expands, more and more regions of the exterior false vacuum, including our CMB sphere, fall into the interior of the bubble. The modes which leave the horizon during inflation at the time when the bubble wall collides with the observable CMB sphere are affected the most. The bubble wall induces non-trivial anisotropic and scale dependent corrections in the two point function of the curvature perturbation. The corrections in the curvature perturbation and the diagonal and off-diagonal elements of CMB power spectrum are estimated.