Scalar perturbations in a primordial inflationary scenario

TL;DR

This paper calculates the spectral index of scalar perturbations in a primordial inflationary model where the transition to the radiative era occurs via a second order phase transition, resulting in a spectral index of 2.

Contribution

It introduces a novel inflationary scenario with a decay of the cosmological term, leading to a thermal spectrum of perturbations and a nearly parameter-independent spectral index of 2.

Findings

Spectral index for scalar perturbations is approximately 2.

Model allows initial conditions with thermal spectrum.

Transition from inflation to radiative era via second order phase transition.

Abstract

We compute the spectral index for scalar perturbations generated in a primordial inflationary model. In this model, the transition of the inflationary phase to the radiative era is achieved through the decay of the cosmological term leading a second order phase transition and the characteristics of the model allow to implement a set of initial conditions where the perturbations display a thermal spectrum when they emerge from the horizon. The obtained value for the spectral index is equal to 2, a result that depends very weakly on the various parameters of the model and on the initial conditions used.