The unified history of the viscous accelerating universe and phase transitions

A.V Astashenok,S.D Odintsov,A.S Tepliakov

doi:10.1016/j.nuclphysb.2021.115646

A.V Astashenok, S.D Odintsov + Show 1 more

Open Access

https://doi.org/10.1016/j.nuclphysb.2021.115646

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Abstract

We propose the unified description of the early acceleration (cosmological inflation) and the present epoch of so called “dark energy”. The inflation can be described by cosmic fluid with van der Waals equation of state and with viscosity term. Viscosity leads to slow-roll inflation with the parameters such as the spectral index, and the tensor-to-scalar ratio in concordance with observational data. Our next step is to modify this equation of state (EoS) to describe the present accelerated expansion. One can add the term into EoS so that the contribution of which is small for inflation but crucial for late-time acceleration. The key point of the model is possible phase transition which leads to decrease of the viscosity. We show that proposed model describes observational data about standard “candles” and correct dependence of Hubble parameter from redshift. Moreover, we propose the possible scenario to resolve dark matter problem.

Highlights

The observational data from Planck [1, 2] confirmed the inflation theory in its simple form [3, 4]
We propose the unified description of the early acceleration and the present epoch of so called “dark energy”
Slow-roll inflation is caused by viscous term in the equation of state being proportional to square of Hubble parameter i.e. the energy density if we neglect the contribution of matter and radiation

Summary

INTRODUCTION

The observational data from Planck [1, 2] confirmed the inflation theory in its simple form [3, 4]. The van der Waals fluid model can account both for the early and late-time accelerated expansion stages of the universe. Various versions of the van der Waals equation can be considered in seeking a better match with the observational data of the Planck satellite [23] Another interesting cosmological phenomenon is accelerated expansion of the Universe [24, 25]. We studied the possible unified description of early and late-time accelerated expansion of universe in terms of the van der Waals equation of state for cosmic fluid including viscous term. Slow-roll inflation is caused by viscous term in the equation of state being proportional to square of Hubble parameter i.e. the energy density if we neglect the contribution of matter and radiation.

BASIC VISCOUS UNIVERSE

LATE-TIME ACCELERATION IN THE MODEL OF FLUID WITH VISCOSITY

COMPARISON WITH PLANCK OBSERVATIONS

Findings

CONCLUSIONS