Cosmological perturbations in transient phantom inflation scenarios

TL;DR

This paper proposes a single-field cosmological model where a phantom inflaton transitions smoothly into a quintessence field, avoiding eternal inflation and providing a unified description of early and late universe dynamics.

Contribution

It introduces a novel transient phantom inflation model with a smooth transition to radiation era, analyzing stability, perturbations, and crossing of the phantom divide line.

Findings

The model achieves a smooth transition between inflation and radiation era.

Conditions for crossing the phantom divide line are identified.

Perturbation analysis shows consistent behavior of gravitational potential and density contrasts.

Abstract

We present a model of inflation where the inflaton is accommodated as a phantom field which exhibits an initial transient pole behavior and then decays into a quintessence field which is responsible for a radiation era. We must stress that the present unified model only deals with a single field and that the transition between two eras is achieved in a smooth way, so the model does not suffer from the eternal inflation issue. We explore the conditions for the crossing of the phantom divide line within the inflationary era along with the structural stability of several critical points. We study the behavior of the phantom field within the slow climb approximation along with the necessary conditions to have sufficient inflation. We also examine the model at the level of classical perturbations within the Newtonian gauge and determine the behavior of the gravitational potential, contrast density and perturbed field near the inflation stage and the subsequent radiation era.