scholarly journals Classical and Quantum f(R) Cosmology: The Big Rip, the Little Rip and the Little Sibling of the Big Rip

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 288
Author(s):  
Teodor Borislavov Vasilev ◽  
Mariam Bouhmadi-López ◽  
Prado Martín-Moruno
Keyword(s):  
Future Evolution ◽  
Quantum Analysis ◽  
Energy Models ◽  
Big Rip ◽  
Phantom Dark Energy ◽  
Gravity Effects ◽  
Theories Of Gravity ◽  
Quantum Treatment ◽  
The Universe ◽  
Quantum Geometrodynamics

The big rip, the little rip and the little sibling of the big rip are cosmological doomsdays predicted by some phantom dark-energy models that could describe the future evolution of our universe. When the universe evolves towards either of these future cosmic events, all bounded structures and, ultimately, space–time itself are ripped apart. Nevertheless, it is commonly believed that quantum gravity effects may smooth or even avoid these classically predicted singularities. In this review, we discuss the classical and quantum occurrence of these riplike events in the scheme of metric f(R) theories of gravity. The quantum analysis is performed in the framework of f(R) quantum geometrodynamics. In this context, we analyze the fulfilment of the DeWitt criterion for the avoidance of these singular fates. This review contains as well new unpublished work (the analysis of the equation of state for the phantom fluid and a new quantum treatment of the big rip and the little sibling of the big rip events).

scholarly journals ATTRACTOR SOLUTION IN COUPLED YANG–MILLS FIELD DARK ENERGY MODELS

2009 ◽  
Vol 18 (09) ◽  
pp. 1331-1342 ◽  
Author(s):  
WEN ZHAO
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
De Sitter ◽  
Yang Mills ◽  
Constraint Equations ◽  
Energy Models ◽  
Big Rip ◽  
Attractor Solution ◽  
The Universe ◽  
Mills Field

We investigate the attractor solution in the coupled Yang–Mills field dark energy models with the general interaction term, and obtain the constraint equations for the interaction if the attractor solution exists. The research also shows that, if the attractor solution exists, the equation of state of dark energy must evolve from wy > 0 to wy ≤ -1, which is slightly suggested by the observation. At the same time, the total equation of state in the attractor solution is w tot = -1, the universe is a de Sitter expansion, and the cosmic big rip is naturally avoided. These features are all independent of the interacting forms.

STATEFINDER PARAMETERS FOR PHANTOM DARK ENERGY

2006 ◽  
Vol 21 (16) ◽  
pp. 1305-1311 ◽  
Author(s):  
PUXUN WU ◽  
HONGWEI YU
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Field Potentials ◽  
Statefinder Parameters ◽  
Phantom Field ◽  
Energy Models ◽  
Phantom Dark Energy ◽  
The Universe

The statefinder parameters were introduced recently to differentiate different dark energy models. In this paper we perform a statefinder diagnostic to the phantom dark energy model with two different phantom field potentials. Our results show that the statefinder diagnostic is rather robust in differentiating not only different dark energy models but also the same kind of models with different potentials which lead to different fate of the universe.

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 Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

scholarly journals Physical Acceptability of the Renyi, Tsallis and Sharma-Mittal Holographic Dark Energy Models in the f(T,B) Gravity under Hubble’s Cutoff

Universe ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 67
Author(s):  
Salim Harun Shekh ◽  
Pedro H. R. S. Moraes ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Field Equations ◽  
Eos Parameter ◽  
Two Fluids ◽  
Gravitational Field Equations ◽  
Energy Models ◽  
Different Types ◽  
The Universe

In the present article, we investigate the physical acceptability of the spatially homogeneous and isotropic Friedmann–Lemâitre–Robertson–Walker line element filled with two fluids, with the first being pressureless matter and the second being different types of holographic dark energy. This geometric and material content is considered within the gravitational field equations of the f(T,B) (where T is the torsion scalar and the B is the boundary term) gravity in Hubble’s cut-off. The cosmological parameters, such as the Equation of State (EoS) parameter, during the cosmic evolution, are calculated. The models are stable throughout the universe expansion. The region in which the model is presented is dependent on the real parameter δ of holographic dark energies. For all δ≥4.5, the models vary from ΛCDM era to the quintessence era.

GROWTH INDEX AND MODIFIED GRAVITY

2011 ◽  
Vol 01 ◽  
pp. 228-233
Author(s):  
YUNGUI GONG
Keyword(s):  
Growth Rate ◽  
Dark Energy ◽  
Modified Gravity ◽  
Growth Index ◽  
Accurate Approximation ◽  
Energy Models ◽  
Λcdm Model ◽  
The Universe ◽  
Matter Energy ◽  
Matter Perturbation

The growth rate of matter perturbation and the expansion rate of the Universe can be used to distinguish modified gravity and dark energy models. Remarkably, the growth rate can be approximated as Ωγ. We discuss the dependence of the growth index γ on the dimensionless matter energy density Ω for a more accurate approximation of the growth factor. The observational data are used to fit different models. The data strongly disfavor the Dvali-Gabadadze-Porrati model. For the ΛCDM model, we find that [Formula: see text]. For the Dvali-Gabadadze-Porrati model, we find that [Formula: see text].

scholarly journals The little sibling of the big rip singularity

2015 ◽  
Vol 24 (10) ◽  
pp. 1550078 ◽  
Author(s):  
Mariam Bouhmadi-López ◽  
Ahmed Errahmani ◽  
Prado Martín-Moruno ◽  
Taoufik Ouali ◽  
Yaser Tavakoli
Keyword(s):  
Blow Up ◽  
Energy Condition ◽  
Cosmic Time ◽  
Energy Conditions ◽  
Accelerating Universe ◽  
Hubble Rate ◽  
Big Rip ◽  
The Status ◽  
The Universe ◽  
Nonlinear Energy

In this paper, we present a new cosmological event, which we named the little sibling of the big rip. This event is much smoother than the big rip singularity. When the little sibling of the big rip is reached, the Hubble rate and the scale factor blow up, but the cosmic derivative of the Hubble rate does not. This abrupt event takes place at an infinite cosmic time where the scalar curvature explodes. We show that a doomsday à la little sibling of the big rip is compatible with an accelerating universe, indeed at present it would mimic perfectly a ΛCDM scenario. It turns out that, even though the event seems to be harmless as it takes place in the infinite future, the bound structures in the universe would be unavoidably destroyed on a finite cosmic time from now. The model can be motivated by considering that the weak energy condition should not be strongly violated in our universe, and it could give us some hints about the status of recently formulated nonlinear energy conditions.

Long-term astrophysical processes

2008 ◽  
Author(s):  
Fred C. Adams
Keyword(s):  
Background Radiation ◽  
Cosmological Parameters ◽  
Future Evolution ◽  
The Future ◽  
The Galaxy ◽  
Microwave Background Radiation ◽  
Type Ia ◽  
Long Time ◽  
Age Of The Universe ◽  
The Universe

As we take a longer-term view of our future, a host of astrophysical processes are waiting to unfold as the Earth, the Sun, the Galaxy, and the Universe grow increasingly older. The basic astronomical parameters that describe our universe have now been measured with compelling precision. Recent observations of the cosmic microwave background radiation show that the spatial geometry of our universe is flat (Spergel et al., 2003). Independent measurements of the red-shift versus distance relation using Type Ia supernovae indicate that the universe is accelerating and apparently contains a substantial component of dark vacuum energy (Garnavich et al., 1998; Perlmutter et al., 1999; Riess et al., 1998). This newly consolidated cosmological model represents an important milestone in our understanding of the cosmos. With the cosmological parameters relatively well known, the future evolution of our universe can now be predicted with some degree of confidence (Adams and Laughlin, 1997). Our best astronomical data imply that our universe will expand forever or at least live long enough for a diverse collection of astronomical events to play themselves out. Other chapters in this book have discussed some sources of cosmic intervention that can affect life on our planet, including asteroid and comet impacts (Chapter 11, this volume) and nearby supernova explosions with their accompanying gamma-rays (Chapter 12, this volume). In the longerterm future, the chances of these types of catastrophic events will increase. In addition, taking an even longer-term view, we find that even more fantastic events could happen in our cosmological future. This chapter outlines some of the astrophysical events that can affect life, on our planet and perhaps elsewhere, over extremely long time scales, including those that vastly exceed the current age of the universe. These projections are based on our current understanding of astronomy and the laws of physics, which offer a firm and developing framework for understanding the future of the physical universe (this topic is sometimes called Physical Eschatology – see the review of ćirković, 2003). Notice that as we delve deeper into the future, the uncertainties of our projections must necessarily grow.

scholarly journals Exploring the deviation of cosmological constant by a generalized pressure parameterization

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
Jun-Chao Wang ◽  
Xin-He Meng
Keyword(s):  
Hubble Constant ◽  
Scalar Fields ◽  
Parametric Model ◽  
Matter Density ◽  
Density Parameter ◽  
Present Value ◽  
Big Rip ◽  
Phantom Scalar ◽  
Ultimate Fate ◽  
The Universe

Abstract We bring forward a generalized pressure (GP) parameterization for dark energy to explore the evolution of the universe. This parametric model has covered three common pressure parameterization types and can be reconstructed as quintessence and phantom scalar fields, respectively. We adopt the cosmic chronometer (CC) datasets to constrain the parameters. The results show that the inferred late-universe parameters of the GP parameterization are (within $$1\sigma $$1σ): the present value of Hubble constant $$H_{0}=(72.30^{+1.26}_{-1.37}) \ \hbox {km s}^{-1}\hbox { Mpc}^{-1}$$H0=(72.30-1.37+1.26)kms-1Mpc-1; the matter density parameter $$\Omega _{\text {m0}}=0.302^{+0.046}_{-0.047}$$Ωm0=0.302-0.047+0.046, and the bias of the universe towards quintessence. Then we perform a dynamic analysis on the GP parameterization and find that there is an attractor or a saddle point in the system corresponding to the different values of the parameters. Finally, we discuss the ultimate fate of the universe under the phantom scenario in the GP parameterization. It is demonstrated that the three cases of pseudo rip, little rip, and big rip are all possible.

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