Spinodal Decomposition and Inflation: Dynamics and Metric Perturbations

TL;DR

This paper investigates how spinodal decomposition during inflation affects metric perturbations, revealing conditions where quantum fluctuations alter the primordial power spectrum and potentially ease fine-tuning issues.

Contribution

It introduces a non-perturbative analysis of spinodal decomposition in inflation, showing its impact on metric fluctuations and primordial spectra, with detailed models and initial state dependence.

Findings

Quantum fluctuations can cause a blue tilt in the power spectrum.

Scalar fluctuation amplitudes can be lower than standard predictions.

The initial inflationary state influences the resulting metric perturbation spectrum.

Abstract

We analyse the dynamics of spinodal decomposition in inflationary cosmology using the closed time path formalism of out of equilibrium quantum field theory combined with the non-perturbative Hartree approximation. In addition to a general analysis, we compute the detailed evolution of two inflationary models of particular importance: lambda Phi^4 new inflation and natural inflation. We compute the metric fluctuations resulting from inflationary phase transitions in the slow roll approximation, showing that there exists a regime for which quantum fluctuations of the inflaton field result in a significant deviation in the predictions of the spectrum of primordial density perturbations from standard results. We provide case examples for which a blue tilt to the power spectrum (i.e. n_s > 1) results from the evolution of a single inflaton field, and demonstrate that field fluctuations may result in a scalar amplitude of fluctuations significantly below standard predictions, resulting in a slight alleviation of the inflationary fine tuning problem. We show explicitly that the metric perturbation spectrum resulting from inflation depends upon the state at the outset of the inflationary phase.