Cosmological Perturbations in Phantom Dark Energy Models

Imanol Albarran,Mariam Bouhmadi-López,João Morais

doi:10.3390/universe3010022

Imanol Albarran, Mariam Bouhmadi-López + Show 1 more

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https://doi.org/10.3390/universe3010022

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Abstract

The ΛCDM paradigm, characterised by a constant equation of state w = − 1 for dark energy, is the model that better fits observations. However, the same observations strongly support the possibility of a dark energy content where the corresponding equation of state is close to but slightly smaller than − 1 . In this regard, we focus on three different models where the dark energy content is described by a perfect fluid with an equation of state w ≲ − 1 which can evolve or not. The three proposals show very similar behaviour at present, while the asymptotic evolution of each model drives the Universe to different abrupt events known as (i) Big Rip; (ii) Little Rip (LR); and (iii) Little Sibling of the Big Rip. With the aim of comparing these models and finding possible imprints in their predicted matter distribution, we compute the matter power spectrum and the growth rate f σ 8 . We conclude that the model which induces a LR seems to be favoured by observations.

Highlights

Since the recent acceleration of the Universe was discovered by SNeIa observations around twenty years ago [1,2], and later corroborated by cosmological and astrophysical observations [3], the current acceleration of the Universe represents one of the most intriguing open problems on cosmology
Only the Big Rip (BR) should be regarded as a true cosmological singularity, since it occurs at a finite cosmic time, while the Little Rip (LR) and Little Sibling of the Big Rip (LSBR) could be understood as a BR somehow driven to an infinite cosmic time; we will refer to them as abrupt events
We analyse the cosmological perturbations for three possible phantom dark energy (DE) scenarios where each of them induces a unique future abrupt event: Big Rip (BR), Little Rip (LR), and Little

Summary

Introduction

Since the recent acceleration of the Universe was discovered by SNeIa observations around twenty years ago [1,2], and later corroborated by cosmological and astrophysical observations [3], the current acceleration of the Universe represents one of the most intriguing open problems on cosmology. Little Sibling of the Big Rip (LSBR): This event occurs at infinite cosmic time, where the scale factor and the Hubble parameter diverge; the cosmic time derivative of Hubble parameter remains finite [14,15]. Only the BR should be regarded as a true cosmological singularity, since it occurs at a finite cosmic time, while the LR and LSBR could be understood as a BR somehow driven to an infinite cosmic time; we will refer to them as abrupt events In all these cases, the Universe ends unavoidably in a classical cosmological doomsday, with all bound structures being ripped apart [12,13,14]. Other works that study the evolution of linear perturbations in doomsday scenarios with various degrees of approximation include [20,21,22], where a kinematical approach is assumed, and [23], where (like in our work) a dynamical model with a specific EoS is employed

Background

Perturbed Equations

Results

Discussion