scholarly journals DARK ENERGY: A UNIFYING VIEW

2008 ◽  
Vol 17 (03n04) ◽  
pp. 651-658 ◽  
Author(s):  
WINFRIED ZIMDAHL
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Interaction Strength ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Strength Parameter ◽  
Expansion Of The Universe ◽  
Pressure Perturbations ◽  
The Universe

Different models of the cosmic substratum which pretend to describe the present stage of accelerated expansion of the Universe, like the ΛCDM model or the Chaplygin gas, can be seen as special realizations of a holographic dark energy cosmology if the option of an interaction between pressureless dark matter and dark energy is taken seriously. The corresponding interaction strength parameter plays the role of a cosmological constant. Differences occur at the perturbative level. In particular, the pressure perturbations are intrinsically nonadiabatic.

ACCELERATED EXPANSION OF THE UNIVERSE THROUGH INTERACTIONS IN THE COSMIC SUBSTRATUM

2009 ◽  
Vol 24 (08n09) ◽  
pp. 1648-1651
Author(s):  
WINFRIED ZIMDAHL
Keyword(s):  
Holographic Dark Energy ◽  
Interaction Strength ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Strength Parameter ◽  
Present Stage ◽  
Generalized Chaplygin Gas ◽  
Expansion Of The Universe ◽  
Pressure Perturbations ◽  
The Universe

Various homogeneous and isotropic cosmological models which describe the present stage of accelerated expansion of the Universe, like the ΛCDM model or (generalized) Chaplygin gas models, can be seen as specific realizations of a holographic dark energy cosmology if an interaction within the cosmic substratum is admitted. The corresponding interaction strength parameter determines the cosmological constant. The transition from decelerated to accelerated expansion arises as a pure interaction phenomenon. Different from the "standard" ΛCDM and Chaplygin gas models, the interaction based approach is characterized by non-adiabatic pressure perturbations.

scholarly journals STATEFINDER DIAGNOSTIC FOR DARK ENERGY MODELS IN BIANCHI I UNIVERSE

2012 ◽  
Vol 21 (05) ◽  
pp. 1250046 ◽  
Author(s):  
M. SHARIF ◽  
RABIA SALEEM
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Ricci Dark Energy ◽  
Generalized Chaplygin Gas ◽  
Bianchi I ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
The Universe

In this paper, we investigate the statefinder, the deceleration and equation of state parameters when universe is composed of generalized holographic dark energy or generalized Ricci dark energy for Bianchi I universe model. These parameters are found for both interacting as well as noninteracting scenarios of generalized holographic or generalized Ricci dark energy with dark matter and generalized Chaplygin gas. We explore these parameters graphically for different situations. It is concluded that these models represent accelerated expansion of the universe.

scholarly journals PRESENT ACCELERATION OF THE UNIVERSE, HOLOGRAPHIC ENERGY AND BRANS–DICKE THEORY

2009 ◽  
Vol 24 (22) ◽  
pp. 1785-1792 ◽  
Author(s):  
B. NAYAK ◽  
L. P. SINGH
Keyword(s):  
Dark Energy ◽  
Power Law ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Accelerated Expansion ◽  
Temporal Behavior ◽  
Holographic Dark Energy Model ◽  
Acceleration Of The Universe ◽  
Expansion Of The Universe ◽  
The Universe

The present-day accelerated expansion of the universe is naturally addressed within the Brans–Dicke theory just by using holographic dark energy model with inverse of Hubble scale as IR cutoff and power law temporal behavior of scale factor. It is also concluded that if the universe continues to expand, then one day it might be completely filled with dark energy.

ENTROPY CORRECTED HOLOGRAPHIC DARK ENERGY f(T) GRAVITY MODEL

2014 ◽  
Vol 29 (02) ◽  
pp. 1450015 ◽  
Author(s):  
M. SHARIF ◽  
SHAMAILA RANI
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Phase Plane ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Statefinder Parameters ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Evolution Trajectory

This paper is devoted to study the power-law entropy corrected holographic dark energy (ECHDE) model in the framework of f(T) gravity. We assume infrared (IR) cutoff in terms of Granda–Oliveros (GO) length and discuss the constructed f(T) model in interacting as well as in non-interacting scenarios. We explore some cosmological parameters like equation of state (EoS), deceleration, statefinder parameters as well as ωT–ωT′ analysis. The EoS and deceleration parameters indicate phantom behavior of the accelerated expansion of the universe. It is mentioned here that statefinder trajectories represent consistent results with ΛCDM limit, while evolution trajectory of ωT–ωT′ phase plane does not approach to ΛCDM limit for both interacting and non-interacting cases.

scholarly journals RECONSTRUCTION OF NEW HOLOGRAPHIC SCALAR FIELD MODELS OF DARK ENERGY IN BRANS–DICKE UNIVERSE

2011 ◽  
Vol 26 (03) ◽  
pp. 191-204 ◽  
Author(s):  
WEI-QIANG YANG ◽  
YA-BO WU ◽  
LI-MIN SONG ◽  
YANG-YANG SU ◽  
JIAN LI ◽  
...  
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Chaplygin Gas ◽  
Energy Model ◽  
Accelerated Expansion ◽  
Holographic Dark Energy Model ◽  
Special Cases ◽  
Expansion Of The Universe

Motivated by the work: K. Karami and J. Fehri, Phys. Lett. B684, 61 (2010) and A. Sheykhi, Phys. Lett. B681, 205 (2009), we generalize their work to the new holographic dark energy model with [Formula: see text] in the framework of Brans–Dicke cosmology. Concretely, we study the correspondence between the quintessence, tachyon, K-essence, dilaton scalar field and Chaplygin gas model with the new holographic dark energy model in the non-flat Brans–Dicke universe. Furthermore, we reconstruct the potentials and dynamics for these models. By analysis we can show that for new holographic quintessence and Chaplygin gas models, if the related parameters to the potentials satisfy some constraints, the accelerated expansion can be achieved in Brans–Dicke cosmology. In particular, the counterparts of fields and potentials in general relativity can describe accelerated expansion of the universe. It is worth stressing that not only can we give some new results in the framework of Brans–Dicke cosmology, but also the previous results of the new holographic dark energy in Einstein gravity can be included as special cases given by us.

Time varying parameter in modified Chaplygin gas cosmology

2020 ◽  
Vol 35 (16) ◽  
pp. 2050128
Author(s):  
Koijam Manihar Singh ◽  
K. L. Mahanta ◽  
Longjam Parbati Devi ◽  
R. R. Sahoo
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Physical World ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Interesting Phenomenon ◽  
Extra Energy ◽  
Time Varying Parameter ◽  
Expansion Of The Universe ◽  
The Universe

In the course of study of the evolution of the universe, it is seen that perhaps the extra energy generated and particles created due to the accelerated expansion of the universe might be absorbed by the dark energy and dark matter which are already existing in this universe. It is found that the energy density of dark energy can be expressed as a function of the energy density of the remaining matter portion of the universe which shows that the different components of the universe are correlated. According to the forms of the different types of interaction occurring between dark energy and the other different contents of the universe it may be possible to utilize the dark energy in different ways as it may take different forms of energy. As an interesting phenomenon, it is also observed that the concept of negative time may exist in this universe, and it may revolutionize some of the original concepts of nature and the physical world.

scholarly journals Observational constraint on interacting Tsallis holographic dark energy in logarithmic Brans–Dicke theory

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
Y. Aditya ◽  
Sanjay Mandal ◽  
P. K. Sahoo ◽  
D. R. K. Reddy
Keyword(s):  
Dark Energy ◽  
Graphical Representation ◽  
Holographic Dark Energy ◽  
Accelerated Expansion ◽  
Observational Constraint ◽  
Tensor Theory ◽  
Dynamical Parameters ◽  
Expansion Of The Universe ◽  
The Stability ◽  
The Universe

AbstractIn this paper, we investigate the dark energy phenomenon by studying the Tsallis holographic dark energy within the framework of Brans–Dicke (BD) scalar–tensor theory of gravity (Brans and Dicke in Phys. Rev. 124:925, 1961). In this context, we choose the BD scalar field $$\phi $$ϕ as a logarithmic function of the average scale factor a(t) and Hubble horizon as the IR cutoff ($$L=H^{-1}$$L=H-1). We reconstruct two cases of non-interacting and interacting fluid (dark sectors of cosmos) scenario. The physical behavior of the models are discussed with the help of graphical representation to explore the accelerated expansion of the universe. Moreover, the stability of the models are checked through squared sound speed $$v_s^2$$vs2. The well-known cosmological plane i.e., $$\omega _{de}-\omega ^{\prime }_{de}$$ωde-ωde′ is constructed for our models. We also include comparison of our findings of these dynamical parameters with observational constraints. It is also quite interesting to mention here that the results of deceleration, equation of state parameters and $$\omega _{de}-\omega ^{\prime }_{de}$$ωde-ωde′ plane coincide with the modern observational data.

scholarly journals Reconstruction of quintessence field for the THDE with swampland correspondence in f(R,T) gravity

2020 ◽  
pp. 2150031 ◽  
Author(s):  
Umesh Kumar Sharma
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Accelerated Expansion ◽  
Eos Parameter ◽  
Expansion Of The Universe ◽  
Hubble Horizon ◽  
Quintessence Field ◽  
The Universe ◽  
Friedmann Robertson Walker ◽  
Quintessence Model

In the present work, we construct the Tsallis holographic quintessence model of dark energy in [Formula: see text] gravity with Hubble horizon as infrared (IR) cut-off. In a flat Friedmann–Robertson–Walker (FRW) background, the correspondence among the energy density of the quintessence model with the Tsallis holographic density permits the reconstruction of the dynamics and the potentials for the quintessence field. The suggested Hubble horizon IR cut-off for the Tsallis holographic dark energy (THDE) density acts for two specific cases: (i) THDE 1 and (ii) THDE 2. We have reconstructed the Tsallis holographic quintessence model in the region [Formula: see text] for the equation of state (EoS) parameter for both the cases. we investigate the behavior of several well-known statefinder quantities, like the deceleration parameter, the jerk and the parameter [Formula: see text]. In addition, the quintessence phase of the THDE models is analyzed with swampland conjecture to describe the accelerated expansion of the Universe.

scholarly journals POLYTROPIC AND CHAPLYGIN f(R)-GRAVITY MODELS

2012 ◽  
Vol 21 (12) ◽  
pp. 1250083 ◽  
Author(s):  
K. KARAMI ◽  
M. S. KHALEDIAN
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
De Sitter Space ◽  
Chaplygin Gas ◽  
Gravity Models ◽  
Accelerated Expansion ◽  
De Sitter ◽  
Expansion Of The Universe ◽  
The Universe

We reconstruct different f(R)-gravity models corresponding to the polytropic, standard Chaplygin, generalized Chaplygin, modified Chaplygin and modified variable Chaplygin gas dark energy (DE) models. We also obtain the equation of state (EoS) parameters of the corresponding f(R)-gravity models which describe the accelerated expansion of the universe. We conclude that although the EoS parameters of the obtained f(R)-gravities can behave like phantom or quintessence DE models, they cannot justify the transition from the quintessence state to the phantom regime. Furthermore, the polytropic and Chaplygin f(R)-gravity models in de Sitter space can satisfy the inflation condition.

scholarly journals Axially symmetric holographic dark energy model with generalized Chaplygin gas in Brans–Dicke theory of gravitation

2016 ◽  
Vol 94 (12) ◽  
pp. 1331-1337
Author(s):  
V.U.M. Rao ◽  
K.V.S. Sireesha
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Distance Modulus ◽  
Axially Symmetric ◽  
Field Equations ◽  
Generalized Chaplygin Gas ◽  
Expansion Of The Universe ◽  
Theory Of Gravitation

In this paper, spatially homogeneous anisotropic axially symmetric holographic dark energy cosmological model with generalized Chaplygin gas is obtained in a scalar–tensor theory of gravitation proposed by Brans and Dicke (Phys. Rev. 124, 925 (1961)). To obtain a determinate solution of the field equations we have used a power law between the metric potentials. It has been found that the anisotropic distribution of dark energy leads to the present accelerated expansion of the Universe. All the models obtained and presented here are expanding, non-rotating, and accelerating. Also some important features of the models including look-back time, distance modulus, and luminosity distance versus redshift, and their significances are discussed.

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