scholarly journals Probing the matter and dark energy sources in a viable Big Rip model of the Universe

2014 ◽  
Vol 29 (25) ◽  
pp. 1450119 ◽  
Author(s):  
Suresh Kumar
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Cosmic Time ◽  
Energy Sources ◽  
De Sitter ◽  
Eos Parameter ◽  
Big Rip ◽  
Λcdm Model ◽  
The Universe ◽  
Dynamical Dark Energy

Chevallier–Polarski–Linder (CPL) parametrization for the equation of state (EoS) of dark energy in terms of cosmic redshift or scale factor have been frequently studied in the literature. In this study, we consider cosmic time-based CPL parametrization for the EoS parameter of the effective cosmic fluid that fills the fabric of spatially flat and homogeneous Robertson–Walker (RW) spacetime in General Relativity. The model exhibits two worthy features: (i) It fits the observational data from the latest H(z) and Union 2.1 SN Ia compilations matching the success of ΛCDM model. (ii) It describes the evolution of the Universe from the matter-dominated phase to the recent accelerating phase similar to the ΛCDM model but leads to Big Rip end of the Universe contrary to the everlasting de Sitter expansion in the ΛCDM model. We investigate the matter and dark energy sources in the model, in particular, behavior of the dynamical dark energy responsible for the Big Rip end of Universe.

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.

scholarly journals Axially magnetized dark energy cosmological model

2019 ◽  
Vol 34 (27) ◽  
pp. 1950217 ◽  
Author(s):  
B. Mishra ◽  
Pratik P. Ray ◽  
S. K. Tripathy ◽  
Kazuharu Bamba
Keyword(s):  
Magnetic Field ◽  
General Relativity ◽  
Dark Energy ◽  
State Parameter ◽  
Substantial Effect ◽  
Anisotropic Universe ◽  
Time Varying ◽  
Big Rip ◽  
Equation Of State Parameter ◽  
The Universe

We investigate the behavior of the skewness parameters for an anisotropic universe in the framework of General Relativity. Non-interacting dark energy is considered in presence of electromagnetic field. A time-varying deceleration parameter simulated by a hybrid scale factor is considered. The dynamics of the universe is investigated in presence and absence of magnetic field. The equation of state parameter of dark energy evolves within the range predicted by the observations. Magnetic field is observed to have a substantial effect on the cosmic dynamics and the skewness parameters. The models discussed here end in a big rip and become isotropic at finite time.

scholarly journals An interacting holographic dark energy model within an induced gravity brane

2020 ◽  
Vol 29 (09) ◽  
pp. 2050066
Author(s):  
Moulay-Hicham Belkacemi ◽  
Zahra Bouabdallaoui ◽  
Mariam Bouhmadi-López ◽  
Ahmed Errahmani ◽  
Taoufik Ouali
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Late Time ◽  
De Sitter ◽  
Ricci Dark Energy ◽  
Induced Gravity ◽  
Big Rip ◽  
Dark Energy Component ◽  
Braneworld Model ◽  
The Universe

In this paper, we present a model for the late-time evolution of the universe where a dark energy-dark matter interaction is invoked. Dark energy is modeled through an holographic Ricci dark energy component. The model is embedded within an induced gravity braneworld model. For suitable choices of the interaction coupling, the big rip and little rip induced by the holographic Ricci dark energy, in a relativistic model and in an induced gravity braneworld model, are removed. In this scenario, the holographic dark energy will have a phantom like behavior even though the brane is asymptotically de Sitter.

scholarly journals A Dark Energy Model with Higher Order Derivatives of H in the f(R,T) Modified Gravity Model

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Antonio Pasqua ◽  
Surajit Chattopadhyay ◽  
Ratbay Myrzakulov
Keyword(s):  
Dark Energy ◽  
Gravity Model ◽  
Modified Gravity ◽  
Hubble Parameter ◽  
Time Derivative ◽  
Cosmic Time ◽  
Late Time ◽  
Eos Parameter ◽  
Curvature And Torsion ◽  
The Universe

We consider a model of dark energy (DE) which contains three terms (one proportional to the squared Hubble parameter, one to the first derivative, and one to the second derivative with respect to the cosmic time of the Hubble parameter) in the light of the f(R,T)=μR+νT modified gravity model, with μ and ν being two constant parameters. R and T represent the curvature and torsion scalars, respectively. We found that the Hubble parameter exhibits a decaying behavior until redshifts z≈-0.5 (when it starts to increase) and the time derivative of the Hubble parameter goes from negative to positive values for different redshifts. The equation of state (EoS) parameter of DE and the effective EoS parameter exhibit a transition from ω<-1 to ω>-1 (showing a quintom-like behavior). We also found that the model considered can attain the late-time accelerated phase of the universe. Using the statefinder parameters r and s, we derived that the studied model can attain the ΛCDM phase of the universe and can interpolate between dust and ΛCDM phase of the universe. Finally, studying the squared speed of sound vs2, we found that the considered model is classically stable in the earlier stage of the universe but classically unstable in the current stage.

scholarly journals A varying dark energy effective speed of sound parameter in the phantom Universe

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Imanol Albarran ◽  
Mariam Bouhmadi-López ◽  
João Marto
Keyword(s):  
Dark Energy ◽  
Speed Of Sound ◽  
Large Scale ◽  
Cosmic Time ◽  
Future Event ◽  
Matter Power Spectrum ◽  
Big Rip ◽  
The Universe ◽  
Potential Sign ◽  
Effective Speed

AbstractWe analyse the phenomenological effects of a varying Dark Energy (DE) effective speed of sound parameter, $$c^{2}_{\text {sd}}$$ c sd 2 , on the cosmological perturbations of three phantom DE models. Each of these models induce a particular abrupt future event known as Big Rip (BR), Little Rip (LR), and Little Sibling of the Big Rip (LSBR). In this class of abrupt events, all the bound structures in the Universe would be ripped apart at a finite cosmic time. We compute the evolution of the perturbations, $$f\sigma _{8}$$ f σ 8 growth rate and forecast the current matter power spectrum. We vary the $$c^{2}_{\text {sd}}$$ c sd 2 parameter in the interval [0, 1] and compute the relative deviation with respect $$c^{2}_{\text {sd}}=1$$ c sd 2 = 1 . In addition, we analyse the effect of gravitational potential sign flip that occurs at very large scale factors as compared with the current one.

scholarly journals CONSTRAINTS ON DARK ENERGY FROM THE OBSERVED EXPANSION OF OUR COSMIC HORIZON

2009 ◽  
Vol 18 (07) ◽  
pp. 1113-1127 ◽  
Author(s):  
FULVIO MELIA
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Cosmic Time ◽  
Accelerating Universe ◽  
De Sitter ◽  
Dark Energy Component ◽  
The Standard Model ◽  
Type Ia ◽  
Age Of The Universe ◽  
The Universe

Within the context of standard cosmology, an accelerating universe requires the presence of a third "dark" component of energy, beyond matter and radiation. The available data, however, are still deemed insufficient to distinguish between an evolving dark energy component and the simplest model of a time-independent cosmological constant. In this paper, we examine the cosmological expansion in terms of observer-dependent coordinates, in addition to the more conventional comoving coordinates. This procedure explicitly reveals the role played by the radius Rh of our cosmic horizon in the interrogation of the data. (In Rindler's notation, Rh coincides with the "event horizon" in the case of de Sitter, but changes in time for other cosmologies that also contain matter and/or radiation.) With this approach, we show that the interpretation of dark energy as a cosmological constant is clearly disfavored by the observations. Within the framework of standard Friedmann–Robertson–Walker cosmology, we derive an equation describing the evolution of Rh, and solve it using the WMAP and Type Ia supernova data. In particular, we consider the meaning of the observed equality (or near-equality) Rh(t0) ≅ ct0, where t0 is the age of the universe. This empirical result is far from trivial, for a cosmological constant would drive Rh(t) toward ct (t is the cosmic time) only once — and that would have to occur right now. Though we are not here espousing any particular alternative model of dark energy, for comparison we also consider scenarios in which dark energy is given by scaling solutions, which simultaneously eliminate several conundrums in the standard model, including the "coincidence" and "flatness" problems, and account very well for the fact that Rh(t0) ≈ ct0.

scholarly journals The Dark Universe as the Ground State of our Quasi-Classical Quantum Cosmology

2021 ◽  
Author(s):  
Gilles Cohen-Tannoudji ◽  
Jean-Pierre Gazeau
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Standard Model ◽  
Particle Physics ◽  
Positive Curvature ◽  
Hidden Variables ◽  
Cosmic Time ◽  
Einstein Condensate ◽  
De Sitter ◽  
The Universe

In the same way as the realization of some of the famous gedanken experiments imagined by the founding fathers of quantum mechanics has recently led to the current renewal of the interpretation of quantum physics, it seems that the most recent progresses of observational astrophysics can be interpreted as the realization of some cosmological gedanken experiments such as the removal from the universe of the whole visible matter or the cosmic time travel leading to a new cosmological standard model. This standard model involves two dark components of the universe, dark energy and dark matter. Whereas dark energy is usually associated with the cosmological constant, we propose to interpret dark matter in terms of a pure vibration energy due to positive curvature and held by quarks and/or by a gluon Bose Einstein condensate accompanying baryonic matter at the hadronization transition from the quark gluon plasma phase to the colorless hadronic phase. Such an interpretation, partially based on mass formulae in terms of energy and spin in de Sitter and Anti de Sitter respectively, would comfort the idea that, apart from the violation of the matter/antimatter symmetry satisfying the Sakharov&rsquo;s conditions, the reconciliation of particle physics and cosmology does not need the recourse to any ad hoc fields, particles or hidden variables.

scholarly journals The Dark Universe as the Ground State of our Quasi-Classical Quantum Cosmology

2021 ◽  
Author(s):  
Gilles Cohen-Tannoudji ◽  
Jean-Pierre Gazeau
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Standard Model ◽  
Particle Physics ◽  
Positive Curvature ◽  
Hidden Variables ◽  
Cosmic Time ◽  
Einstein Condensate ◽  
De Sitter ◽  
The Universe

In the same way as the realization of some of the famous gedanken experiments imagined by the founding fathers of quantum mechanics has recently led to the current renewal of the interpretation of quantum physics, it seems that the most recent progresses of observational astrophysics can be interpreted as the realization of some cosmological gedanken experiments such as the removal from the universe of the whole visible matter or the cosmic time travel leading to a new cosmological standard model. This standard model involves two dark components of the universe, dark energy and dark matter. Whereas dark energy is usually associated with the cosmological constant, we propose to interpret dark matter in terms of a pure vibration energy due to positive curvature and held by quarks and/or by a gluon Bose Einstein condensate accompanying baryonic matter at the hadronization transition from the quark gluon plasma phase to the colorless hadronic phase. Such an interpretation, partially based on mass formulae in terms of energy and spin in de Sitter and Anti de Sitter respectively, would comfort the idea that, apart from the violation of the matter/antimatter symmetry satisfying the Sakharov&rsquo;s conditions, the reconciliation of particle physics and cosmology does not need the recourse to any ad hoc fields, particles or hidden variables.

scholarly journals Growth of perturbations using Lambert W equation of state

2021 ◽  
pp. 2150139
Author(s):  
Manisha Banerjee ◽  
Sudipta Das ◽  
Abdulla Al Mamon ◽  
Subhajit Saha ◽  
Kazuharu Bamba
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
State Parameter ◽  
Mathematical Function ◽  
Eos Parameter ◽  
First Case ◽  
Dark Energy Component ◽  
Text Model ◽  
The Universe ◽  
Dynamical Dark Energy

Recently, a novel equation of state (EoS) parameter for dark energy has been introduced which deals with a special mathematical function, known as the Lambert [Formula: see text] function. In this paper, we study the effect on the growth of perturbations for the Lambert [Formula: see text] dark energy model. We perform the analysis for two different approaches. In the first case, we consider the universe to be filled with two different fluid components, namely, the baryonic matter component and the Lambert [Formula: see text] dark energy component, while in the second case, we consider that there is a single fluid component in the universe whose equation of state parameter is described by the Lambert [Formula: see text] function. We then compare the growth rates of Lambert [Formula: see text] model with that for a standard [Formula: see text]CDM model as well as the CPL model. Our results indicate that the presence of Lambert [Formula: see text] dynamical dark energy sector changes the growth rate and affects the matter fluctuations in the universe to a great extent.

Cosmological spacetimes

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Cosmological Model ◽  
Large Scale ◽  
Cosmic Time ◽  
De Sitter ◽  
Matter Distribution ◽  
Observable Universe ◽  
Cosmological Principle ◽  
Riemannian Spacetime ◽  
The Universe ◽  
Copernican Principle

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

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