Om diagnostic for dilaton dark energy

Huang, Z. G.; Lu, H. Q.; Zhang, K.

doi:10.1007/s10509-010-0437-4

Cited by 9 publications

(5 citation statements)

References 53 publications

(48 reference statements)

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“…The Om(z) diagnostic [39] has been proposed to differentiate C DM to other DE models. Many authors [71][72][73] have studied the DE models based on Om(z) diagnostic. Its constant behaviour with respect to z represents that DE is a cosmological constant ( C DM).…”

Section: Om Diagnosticmentioning

confidence: 99%

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

Singh

Srivastava

2018

Eur. Phys. J. C

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In this work, we study a flat FriedmannRobertson-Walker universe filled with dark matter and viscous new holographic dark energy. We present four possible solutions of the model depending on the choice of the viscous term. We obtain the evolution of the cosmological quantities such as scale factor, deceleration parameter and transition redshift to observe the effect of viscosity in the evolution. We also emphasis upon the two independent geometrical diagnostics for our model, namely the statefinder and the Om diagnostics. In the first case we study new holographic dark energy model without viscous and obtain power-law expansion of the universe which gives constant deceleration parameter and statefinder parameters. In the limit of the parameter, the model approaches to C DM model. In new holographic dark energy model with viscous, the bulk viscous coefficient is assumed as ζ = ζ 0 + ζ 1 H , where ζ 0 and ζ 1 are constants, and H is the Hubble parameter. In this model, we obtain all possible solutions with viscous term and analyze the expansion history of the universe. We draw the evolution graphs of the scale factor and deceleration parameter. It is observed that the universe transits from deceleration to acceleration for small values of ζ in late time. However, it accelerates very fast from the beginning for large values of ζ . By illustrating the evolutionary trajectories in r −s and r −q planes, we find that our model behaves as an quintessence like for small values of viscous coefficient and a Chaplygin gas like for large values of bulk viscous coefficient at early stage. However, model has close resemblance to that of the C DM cosmology in late time. The Om has positive and negative curvatures for phantom and quintessence models, respectively depending on ζ . Our study shows that the bulk viscosity plays very important role in the expansion history of the universe. a

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Section: Om Diagnosticmentioning

confidence: 99%

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

Singh

Srivastava

2018

Eur. Phys. J. C

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“…It relies on first order derivative so it is simpler diagnostic as compare to the statefinder diagnostic when it is applied to the cosmological observation [47]. Many authors [48][49][50]…”

Section: Deceleration Parametermentioning

confidence: 99%

Cosmological aspects of sound speed parameterizations in fractal universe

et al. 2019

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In the framework of fractal universe, the unified models of dark energy and dark matter are being presented with the background of homogenous and isotropic FLRW geometry. The aspects of fractal cosmology helps in better understanding of the universe in different dimensions. Relationship between the squared speed of the sound and the equation of state parameter is the key feature of these models. We have used constant as well as variable forms of speed of sound and express it as a function of equation of state parameter. By utilizing the four different forms of speed of sound, we construct the energy densities and pressures for these models and then various cosmological parameters like hubble parameter, EoS parameter, deceleration parameter and Om-diagnostic are investigated. Graphical analysis of these parameters show that in most of the cases EoS parameters and trajectories of Om-diagnostic corresponds to the quintessence like nature of the universe and the deceleration parameters represent accelerated and decelerated phase. In the end, we remark that cosmological analysis of these models indicates that these models correspond to different well known dark energy models.

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“…Om has zero, negative and positive curvatures for ΛCDM , quintessence and phantom models, respectively. Many authors [83][84][85] have studied the DE models based on Om(z) diagnostic. Following Sahni et al [82], Om(z) for spatially flat universe is defined as…”

Section: Om Diagnosticmentioning

confidence: 99%

New holographic dark energy model with bulk viscosity in f(R, T) gravity

Singh

Srivastava

2019

Indian J Phys

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In this paper, bulk viscosity is introduced in new holographic dark energy (HDE) to describe the effects of cosmic non-perfect fluid on the evolution of the universe in modified f (R, T ) gravity. Assuming f (R, T ) = R+λT , where R is the Ricci scalar, T , the trace of energy-momentum tensor and λ is a constant, we derive a general function of Hubble parameter with bulk viscous form to provide a procedure for the viscous new HDE model building. Especially, we assume the total bulk viscosity coefficient proportional to the velocity of the expansion of the universe in such a way that ζ = ζ 0 + ζ 1 H. We obtain the solutions of the scale factor and deceleration parameter and classify all the possible scenarios (deceleration, acceleration and their transition) with different parameter regions chosen properly for positive and negative ranges of λ, and ζ 0 and ζ 1 to analyze the evolution of the universe. It is observed that there is a transition from decelerated phase to accelerated phase at early or late time depending on the values of viscous terms. For large values of viscous terms it always accelerates through out the evolution. Furthermore, we also investigate the statefinder pair {r, s} and Om diagnostics for the viscous new HDE model to discriminate with other existing DE models. The model evolution behaviors are shown in the planes of r − s, r − q and Om − z. It is found that behavior of trajectories in different planes depend on the bulk viscous coefficient. A small combination of ζ 0 and ζ 1 gives the quintessence like behavior whereas large combination of these two terms give Chaplygin gas like model. However, both the model approaches to ΛCDM model in late time of evolution of the universe. Our viscous model is also different from other existing dark energy models. The evolution of effective equation of state parameter is -0.9745 which is very close to the observation. The entropy and generalized second law of thermodynamics are valid for this model under some constraints of bulk viscous coefficient. The analysis shows that the dark energy phenomena may be explained as the effect of bulk viscosity in the cosmic medium.

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Om diagnostic for dilaton dark energy

Cited by 9 publications

References 53 publications

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

Cosmological aspects of sound speed parameterizations in fractal universe

New holographic dark energy model with bulk viscosity in f(R, T) gravity

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