Analytical treatment of small scales matter power spectrum in coupled scalar field (CSF) cosmology

Fargiza A M Mulki,Hesti Wulandari,W.K Ng,S.C.C Ng,A Yang,C.H Sow,A.H Chan

doi:10.1051/epjconf/202024002003

Fargiza A M Mulki, Hesti Wulandari + Show 5 more

Open Access

https://doi.org/10.1051/epjconf/202024002003

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Abstract

In this paper, we reconstruct matter power spectrum of a cosmological model in which coupled scalar field acts as dark energy. The coupled scalar field (CSF) dark energy we propose here is a generalized model of quintessence, k-essence or phantom coupled to dark matter (non-baryonic matter) via a coupling constant. The existence of coupling between dark energy and matter allows energy to transfer between them, which may give rise to different observational signatures, especially at perturbation level, including matter power spectrum. In this work, through analytical exploration we studied that possible signature in matter power spectrum that maybe induced by this mode.

Highlights

The standard model of cosmology, is constructed by two dark components of the universe, namely the cosmological constant and cold dark matter
We will construct matter power spectrum originally starting from coupled scalar field (CSF)-DE model, in which all the aforementioned equations will analytically be transformed into observable parameters
For small scales in which perturbation enter the horizon at radiation dominated era and undergo physical processes generated during radiation era, matter era, and coupled scalar field era

Summary

Introduction

The standard model of cosmology (the ΛCDM model), is constructed by two dark components of the universe, namely the cosmological constant and cold dark matter. Designating the cosmological constant as vacuum energy stored in spacetime leading to severe fine tuning problem [2] This serious problem has evoked persistent interests in extending cosmology beyond the standard model, including proposals of dynamically changing scalar field as alternative models of dark energy, such as quintessence, k-essence, and phantom [3 – 10]. Based on the results in eq (5) and (6) we see that, for ordinary fields, the existence of coupling Q triggers additional growth rate so that structures grow faster than in the cases of uncoupled and ΛCDM models. Phantom fields with negative kinetic energy invert the flow of energy current, so that structures grow slower than in the cases of uncoupled and ΛCDM models. As for the time in the distant future, both ordinary and phantom fields will break down the existing structures, but with a little distinction between them, i.e. in phantom scenario the decay occurs stronger than as in the ordinary one, indicating an explosive expansion of the background universe or big rip

Matter Power Spectrum

Matter transfer function

Power spectrum on small scales

Conclusion