Cosmological perturbations from an inhomogeneous phase transition

TL;DR

This paper explores how inhomogeneous phase transitions during inflation, caused by long-wavelength scalar field fluctuations, can generate cosmological perturbations, potentially leading to observable non-Gaussian features.

Contribution

It introduces a novel mechanism where inhomogeneous phase transitions produce metric perturbations, highlighting their role as a generic source of non-Gaussianity in cosmology.

Findings

Phase transitions can generate superhorizon fluctuations due to inhomogeneous couplings.

Cosmological perturbations may originate at the electroweak phase transition.

Inhomogeneous phase transitions are a potential source of non-Gaussianity.

Abstract

A mechanism for generating metric perturbations in inflationary models is considered. Long-wavelength inhomogeneities of light scalar fields in a decoupled sector may give rise to superhorizon fluctuations of couplings and masses in the low-energy effective action. Cosmological phase transitions may then occur that are not simultaneous in space, but occur with time lags in different Hubble patches that arise from the long-wavelength inhomogeneities. Here an interesting model in which cosmological perturbations may be created at the electroweak phase transition is considered. The results show that phase transitions may be a generic source of non-Gaussianity.