Dynamics and constraints of the Unified Dark Matter flat cosmologies

TL;DR

This paper analyzes scalar field flat cosmological models within the Unified Dark Matter scenario, deriving analytical solutions, constraining parameters with observational data, and comparing with other dark energy models to assess their viability.

Contribution

It provides analytical solutions for UDM models, constrains their parameters with recent data, and compares their dynamics with standard dark energy models, highlighting similarities and differences.

Findings

UDM models can accommodate accelerated expansion.

Constraints on UDM parameters align with observational data.

Differences between UDM and other dark energy models are notable at high redshifts.

Abstract

We study the dynamics of the scalar field FLRW flat cosmological models within the framework of the Unified Dark Matter (UDM) scenario. In this model we find that the main cosmological functions such as the scale factor of the Universe, the scalar field, the Hubble flow and the equation of state parameter are defined in terms of hyperbolic functions. These analytical solutions can accommodate an accelerated expansion, equivalent to either the dark energy or the standard $\Lambda$ models. Performing a joint likelihood analysis of the recent supernovae type Ia data and the Baryonic Acoustic Oscillations traced by the SDSS galaxies, we place tight constraints on the main cosmological parameters of the UDM cosmological scenario. Finally, we compare the UDM scenario with various dark energy models namely $\Lambda$ cosmology, parametric dark energy model and variable Chaplygin gas. We find that the UDM scalar field model provides a large and small scale dynamics which are in fair agreement with the predictions by the above dark energy models although there are some differences especially at high redshifts.