Properties of singularities in (phantom) dark energy universe

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Abstract

The properties of future singularities are investigated in the universe dominated by dark energy including the phantom-type fluid. We classify the finite-time singularities into four classes and explicitly present the models which give rise to these singularities by assuming the form of the equation of state of dark energy. We show the existence of a stable fixed point with an equation of state \(w<-1\) and numerically confirm that this is actually a late-time attractor in the phantom-dominated universe. We also construct a phantom dark energy scenario coupled to dark matter that reproduces singular behaviors of the Big Rip type for the energy density and the curvature of the universe. The effect of quantum corrections coming from conformal anomaly can be important when the curvature grows large, which typically moderates the finite-time singularities.

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Exponential potentials and cosmological scaling solutions

David Wands, Edmund J. Copeland, Andrew Liddle (1997)

We present a phase-plane analysis of cosmologies containing a barotropic fluid with equation of state \(p_\gamma = (\gamma-1) \rho_\gamma\), plus a scalar field \(\phi\) with an exponential potential \(V \propto \exp(-\lambda \kappa \phi)\) where \(\kappa^2 = 8\pi G\). In addition to the well-known inflationary solutions for \(\lambda^2 3\gamma\) in which the scalar field energy density tracks that of the barotropic fluid (which for example might be radiation or dust). We show that the scaling solutions are the unique late-time attractors whenever they exist. The fluid-dominated solutions, where \(V(\phi)/\rho_\gamma \to 0\) at late times, are always unstable (except for the cosmological constant case \(\gamma = 0\)). The relative energy density of the fluid and scalar field depends on the steepness of the exponential potential, which is constrained by nucleosynthesis to \(\lambda^2 > 20\). We show that standard inflation models are unable to solve this `relic density' problem.

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Late-time cosmology in (phantom) scalar-tensor theory: dark energy and the cosmic speed-up

Sergei D. Odintsov, Shin'ichi Nojiri, Emilio Elizalde (2004)

We consider late-time cosmology in a (phantom) scalar-tensor theory with an exponential potential, as a dark energy model with equation of state parameter close to -1 (a bit above or below this value). Scalar (and also other kinds of) matter can be easily taken into account. An exact spatially-flat FRW cosmology is constructed for such theory, which admits (eternal or transient) acceleration phases for the current universe, in correspondence with observational results. Some remarks on the possible origin of the phantom, starting from a more fundamental theory, are also made. It is shown that quantum gravity effects may prevent (or, at least, delay or soften) the cosmic doomsday catastrophe associated with the phantom, i.e. the otherwise unavoidable finite-time future singularity (Big Rip). A novel dark energy model (higher-derivative scalar-tensor theory) is introduced and it is shown to admit an effective phantom/quintessence description with a transient acceleration phase. In this case, gravity favors that an initially insignificant portion of dark energy becomes dominant over the standard matter/radiation components in the evolution process.

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The final state and thermodynamics of dark energy universe

Shin'ichi Nojiri, Sergei D. Odintsov (2004)

As it follows from the classical analysis, the typical final state of the dark energy universe where dominant energy condition is violated is finite time, sudden future singularity (Big Rip). For a number of dark energy universes (including scalar phantom and effective phantom theories as well as specific quintessence model) we demonstrate that quantum effects play the dominant role near Big Rip, driving the universe out of future singularity (or, at least, making it milder). As a consequence, the entropy bounds with quantum corrections become well-defined near Big Rip. Similarly, black holes mass loss due to phantom accretion is not so dramatic as it was expected: masses do not vanish to zero due to transient character of phantom evolution stage. Some examples of cosmological evolution for negative, time-dependent equation of state are also considered with the same conclusions. The application of negative entropy (or negative temparature) occurence in the phantom thermodynamics is briefly discussed.

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Publication date Created: 05 January 2005

Publication date Updated: 2005-03-18

Article

DOI: 10.1103/PhysRevD.71.063004

ArXiV ID: hep-th/0501025

SO-VID: 4d3a9169-776b-4f84-80db-ac7c8af6cbda

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Journal reference Phys.Rev.D71:063004,2005

Comments 17 pages, 6 figures, references are added, version to appear in Physical Review D

Properties of singularities in (phantom) dark energy universe

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Renewable Energy - Geothermal

Most cited references 4

Exponential potentials and cosmological scaling solutions

Late-time cosmology in (phantom) scalar-tensor theory: dark energy and the cosmic speed-up

The final state and thermodynamics of dark energy universe

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