Two-component perfect fluid in FRW universe

TL;DR

This paper presents a cosmological model with a two-component perfect fluid that describes the universe's evolution from inflation to dark energy domination, including transitions between radiation, matter, and cosmic string eras.

Contribution

It introduces a novel two-component fluid model with energy exchange, unifying different cosmic epochs within a single framework and analytically continuing energy density through inflation.

Findings

Derived functions for Hubble rate, energy density, and deceleration parameter over time.

Model captures smooth transitions between radiation, matter, and cosmic string eras.

Describes inflation as an analytic continuation of early universe energy density.

Abstract

We consider the cosmological model which allows to describe on equal footing the evolution of matter in the universe on the time interval from the inflation till the domination of dark energy. The matter is considered as a two-component perfect fluid imitated by homogeneous scalar fields between which there is energy exchange. Dark energy is represented by the cosmological constant, which is supposed invariable during the whole evolution of the universe. The matter changes its equation of state with time, so that the era of radiation domination in the early universe smoothly passes into the era of a pressureless gas, which then passes into the late-time epoch, when the matter is represented by a gas of low-velocity cosmic strings. The inflationary phase is described as an analytic continuation of the energy density in the very early universe into the region of small negative values of the parameter which characterizes typical time of energy transfer from one matter component to another. The Hubble expansion rate, energy density of the matter, energy density parameter, and deceleration parameter as functions of time are found.