Abstract
We analyze and review cosmological models in which the dynamics of a single scalar field accounts for a unified description of the Dark Matter and Dark Energy sectors, dubbed Unified Dark Matter (UDM) models. In this framework, we consider the general Lagrangian of k‐essence, which allows to find solutions around which the scalar field describes the desired mixture of Dark Matter and Dark Energy. We also discuss static and spherically symmetric solutions of Einstein′s equations for a scalar field with noncanonical kinetic term, in connection with galactic halo rotation curves.
Highlights
In the last few decades a standard cosmological “Big Bang” model has emerged, based on Einstein’s theory of gravity, General Relativity
Model, as shown in [27] for the generalised Chaplygin gas and in [39] for the affine adiabatic model. (From the point of view of the analysis of models in the p − ρ plane of Figure 1, the constraints found by Sandvik et al [27] on the generalised Chaplygin gas Unified Dark Matter (UDM) models and by [39] on the affine UDM models amount to say that the curves representing these models are indistinguishable from the horizontal ΛCDM line.) In other words, one would conclude that any UDM model should satisfy the condition cs2 1 at all times, so that kJ2 k2 for all scales of cosmological interest, in turn giving an evolution for the gravitational potential Φ as in (23)
In this work we explored the possibility that the dynamics of a single scalar field can account for a unified description of the Dark Matter and Dark Energy sectors, leading to a Unified Dark Matter (UDM) model
Summary
In the last few decades a standard cosmological “Big Bang” model has emerged, based on Einstein’s theory of gravity, General Relativity. We show that these models have only one late-time attractor with equation of state equal to minus one (cosmological constant), studying all possible solutions near the attractor which describes a unified dark matter fluid; see [33]. In the appendix, for completeness we provide the spherical collapse top-hat solution for UDM models based on purely kinetic scalar eld Lagrangians, which allow us to connect the cosmological solutions to the static configurations
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