Phantom dark energy, cosmic doomsday, and the coincidence problem

2005 ◽  
Vol 71 (6) ◽  
Author(s):  
Robert J. Scherrer
Keyword(s):  
Dark Energy ◽  
Coincidence Problem ◽  
Phantom Dark Energy

SCALING DARK ENERGY IN A FIVE-DIMENSIONAL BOUNCING COSMOLOGICAL MODEL

2005 ◽  
Vol 14 (11) ◽  
pp. 1947-1957 ◽  
Author(s):  
LIXIN XU ◽  
HONGYA LIU
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Model ◽  
Cold Dark Matter ◽  
Coincidence Problem ◽  
Energy Models ◽  
Phantom Dark Energy ◽  
Hyperbolic Form ◽  
Induced Matter ◽  
The Universe

We consider a five-dimensional Ricci flat bouncing cosmological model in which the four-dimensional induced matter contains two components at late times — the cold dark matter (CDM) + baryons and dark energy. We find that the arbitrary function f(z) contained in the solution plays a similar role as the potential V(ϕ) in quintessence and phantom dark energy models. To resolve the coincidence problem, it is generally believed that there is a scaling stage in the evolution of the universe. We analyze the condition for this stage and show that a hyperbolic form of the function f(z) can work well in this property. We find that during the scaling stage (before z ≈ 2), the dark energy behaves like (but not identical to) a cold dark matter with an adiabatic sound speed [Formula: see text] and px ≈ 0. After z ≈ 2, the pressure of the dark energy becomes negative. The transition from deceleration to acceleration happens at zT ≈ 0.8 which, as well as other predictions of the 5D model, agrees with current observations.

scholarly journals Late Time Attractors of Some Varying Chaplygin Gas Cosmological Models

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 769
Author(s):  
Martiros Khurshudyan ◽  
Ratbay Myrzakulov
Keyword(s):  
Dark Energy ◽  
Gravitational Interaction ◽  
Chaplygin Gas ◽  
Cosmological Models ◽  
Late Time ◽  
Time Behavior ◽  
Coincidence Problem ◽  
Energy Models ◽  
Non Linear ◽  
Bayesian Machine Learning

The goal of this paper is to study new cosmological models where the dark energy is a varying Chaplygin gas. This specific dark energy model with non-linear EoS had been often discussed in modern cosmology. Contrary to previous studies, we consider new forms of non-linear non-gravitational interaction between dark matter and assumed dark energy models. We applied the phase space analysis allowing understanding the late time behavior of the models. It allows demonstrating that considered non-gravitational interactions can solve the cosmological coincidence problem. On the other hand, we applied Bayesian Machine Learning technique to learn the constraints on the free parameters. In this way, we gained a better understanding of the models providing a hint which of them can be ruled out. Moreover, the learning based on the simulated expansion rate data shows that the models cannot solve the H0 tension problem.

scholarly journals INTERACTION BETWEEN DARK ENERGY AND DARK MATTER: OBSERVATIONAL CONSTRAINTS FROM OHD, BAO, CMB AND SNe Ia

2013 ◽  
Vol 22 (14) ◽  
pp. 1350082 ◽  
Author(s):  
SHUO CAO ◽  
NAN LIANG
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Observational Constraints ◽  
Coincidence Problem ◽  
Cosmological Constraints ◽  
Coincidence Index ◽  
Acceleration Of The Universe ◽  
Interaction Term ◽  
Negative Coupling ◽  
The Universe

In order to test if there is energy transfer between dark energy (DE) and dark matter (DM), we investigate cosmological constraints on two forms of nontrivial interaction between the DM sector and the sector responsible for the acceleration of the universe, in light of the newly revised observations including OHD, CMB, BAO and SNe Ia. More precisely, we find the same tendencies for both phenomenological forms of the interaction term Q = 3γHρ, i.e. the parameter γ to be a small number, |γ| ≈ 10-2. However, concerning the sign of the interaction parameter, we observe that γ > 0 when the interaction between dark sectors is proportional to the energy density of dust matter, whereas the negative coupling (γ < 0) is preferred by observations when the interaction term is proportional to DE density. We further discuss two possible explanations to this incompatibility and apply a quantitative criteria to judge the severity of the coincidence problem. Results suggest that the γm IDE model with a positive coupling may alleviate the coincidence problem, since its coincidence index C is smaller than that for the γd IDE model, the interacting quintessence and phantom models by four orders of magnitude.

scholarly journals Phantom dark energy as an effect of bulk viscosity

2013 ◽  
Vol 88 (12) ◽  
Author(s):  
Hermano Velten ◽  
Jiaxin Wang ◽  
Xinhe Meng
Keyword(s):  
Dark Energy ◽  
Bulk Viscosity ◽  
Phantom Dark Energy

scholarly journals Exploring the dark universe: Constraints on dynamical dark energy models from CMB, BAO and growth rate measurements

2019 ◽  
Vol 28 (09) ◽  
pp. 1950118 ◽  
Author(s):  
Alexander Bonilla Rivera ◽  
Jorge Enrique García-Farieta
Keyword(s):  
Dark Energy ◽  
Observational Data ◽  
Cosmological Parameters ◽  
Growth Parameter ◽  
Information Criteria ◽  
Fine Tuning ◽  
Coincidence Problem ◽  
Shift Parameter ◽  
History Of ◽  
Dynamical Dark Energy

In order to explain the current acceleration of the universe, the fine-tuning problem of the cosmological constant [Formula: see text] and the cosmic coincidence problem, different alternative models have been proposed in the literature. We use the most recent observational data from CMB (Planck 2018 final data release) and LSS (SDSS, WiggleZ, VIPERS) to constrain dynamical dark energy (DE) models. The CMB shift parameter, which traditionally has been used to determine the main cosmological parameters of the standard model [Formula: see text], is employed in addition to data from redshift-space distortions through the growth parameter [Formula: see text] to constrain the mass variance [Formula: see text]. BAO data are also used to study the history of the cosmological expansion and the main properties of DE. From the evolution of [Formula: see text], we found a slowdown of acceleration behavior at low redshifts, and by using the Akaike and Bayesian Information Criteria (AIC, BIC), we discriminate different models to find those that are better suited to the observational data, finding that the interacting dark energy (IDE) model is the most favored by observational data, including information from SNIa and Hz. The analysis shows that the IDE model is followed closely by EDE and [Formula: see text] models, which in some cases fit better the observational data with individual probes.

scholarly journals Properties of singularities in the (phantom) dark energy universe

2005 ◽  
Vol 71 (6) ◽  
Author(s):  
Shin’ichi Nojiri ◽  
Sergei D. Odintsov ◽  
Shinji Tsujikawa
Keyword(s):  
Dark Energy ◽  
Phantom Dark Energy

Exact solution of phantom dark energy model

2010 ◽  
Vol 19 (11) ◽  
pp. 119801 ◽  
Author(s):  
Wen-Fu Wang ◽  
Zheng-Wei Shui ◽  
Bin Tang
Keyword(s):  
Exact Solution ◽  
Dark Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Phantom Dark Energy
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