Theoretical Models of Dark Energy

Yoo, Jaewon; Watanabe, Yuki

doi:10.1142/s0218271812300029

Cited by 218 publications

(177 citation statements)

References 108 publications

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“…In order to solve the mentioned problems various models of dynamical DE models have been introduced without violating/recovering symmetries of LSU [5,6]. Among DE models are quintessence, k-essence, tachyonic, phantom and quinton DE models, as well as dark fluids like Chaplygin gas (and its modifications), van der Waals gas and polytropic gas involving also viscosity and references therein.…”

Section: The Energy Condition Mathematical Expressionmentioning

confidence: 99%

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On the Phenomenology of an Accelerated Large-Scale Universe

Khurshudyan

2016

Symmetry

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Abstract:In this review paper, several new results towards the explanation of the accelerated expansion of the large-scale universe is discussed. On the other hand, inflation is the early-time accelerated era and the universe is symmetric in the sense of accelerated expansion. The accelerated expansion of is one of the long standing problems in modern cosmology, and physics in general. There are several well defined approaches to solve this problem. One of them is an assumption concerning the existence of dark energy in recent universe. It is believed that dark energy is responsible for antigravity, while dark matter has gravitational nature and is responsible, in general, for structure formation. A different approach is an appropriate modification of general relativity including, for instance, f (R) and f (T) theories of gravity. On the other hand, attempts to build theories of quantum gravity and assumptions about existence of extra dimensions, possible variability of the gravitational constant and the speed of the light (among others), provide interesting modifications of general relativity applicable to problems of modern cosmology, too. In particular, here two groups of cosmological models are discussed. In the first group the problem of the accelerated expansion of large-scale universe is discussed involving a new idea, named the varying ghost dark energy. On the other hand, the second group contains cosmological models addressed to the same problem involving either new parameterizations of the equation of state parameter of dark energy (like varying polytropic gas), or nonlinear interactions between dark energy and dark matter. Moreover, for cosmological models involving varying ghost dark energy, massless particle creation in appropriate radiation dominated universe (when the background dynamics is due to general relativity) is demonstrated as well. Exploring the nature of the accelerated expansion of the large-scale universe involving generalized holographic dark energy model with a specific Nojiri-Odintsov cut-off is presented to finalize the paper.

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Section: The Energy Condition Mathematical Expressionmentioning

confidence: 99%

“…In this case according to recent understanding of symmetries and physics of LSU, dark energy (DE) (≈70%) should be used to provide acceleration to expanding universe [5,6]. On the other hand, DE is not enough and according to astrophysical data, dark matter (DM) should be involved in the energy budget of universe [7,8].…”

Section: Introductionmentioning

confidence: 99%

On the Phenomenology of an Accelerated Large-Scale Universe

Khurshudyan

2016

Symmetry

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“…This allows the proposal for a wide range of types of DE candidates besides the pure positive CC like: quintessence, K-essence, chameleon field, f (R) gravity and others; for a review see [13,14] and references therein.…”

Section: Introductionmentioning

confidence: 99%

Running vacuum cosmological models: linear scalar perturbations

Perico

Tamayo

2017

J. Cosmol. Astropart. Phys.

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In cosmology, phenomenologically motivated expressions for running vacuum are commonly parametrized as linear functions Λ(H 2 ) or Λ(R). Such kind of models assume an equation of state for vacuum given by P Λ = − ρ Λ , relating their background pressure P Λ and mean energy density ρ Λ ≡ Λ/8πG. This equation of state requires that the dynamic for vacuum is due to the energy exchange with the material species. Most of the approaches to background level consider only the energy exchange between vacuum and the transient dominant material component of the universe. We extend such models assuming the running vacuum as the sum of independent contributions ρ Λ = i ρ Λi , associated with (and interacting with) each of the i material species. We derive the linear scalar perturbations for two running scenarios, modeling its cosmic evolution and identifying their different imprints on the cosmic microwave background anisotropies and the matter power spectrum. In the Λ(H 2 ) scenario the running vacuum are coupled with all the material species in the universe, whereas the Λ(R) description only leads to coupling between vacuum and the non-relativistic matter components; which produces different imprints of the two models on the matter power spectrum. A comparison with the Planck 2015 data was made in order to constrain the free parameters of the models. In the case of the Λ(H 2 ) model, it was found that Ω Λ = 0.705 ± 0.027 and H 0 = 69.6 ± 2.9 km M pc −1 s −1 , which diminish the tension with the low redshift expectations. * elduartep@usp.br †

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“…It is indeed possible to reconstruct the redshift dependence of w, a key feature to distinguish between the cosmological constant, which predicts a constant w, and alternative models which generally give an effecitve equation of state parameter that varies with redshift (see e.g. [13,14]). …”

Section: Introductionmentioning

confidence: 99%

New constraints on the dark energy equation of state

Said

Baccigalupi²,

Martinelli³

et al. 2013

Phys. Rev. D

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We combine recent measurements of Cosmic Microwave Background Anisotropies, Supernovae luminosity distances and Baryonic Acoustic Oscillations to derive constraints on the dark energy equation of state w in the redshift range 0 < z < 2, using a principal components approach. We find no significant deviations from the expectations of a cosmological constant. However, combining the datasets we find slight indication for w < −1 at low redshift, thus highlighting how these datasets prefer a non-constant w. Nevertheless the cosmological constant is still in agreement with these observations, while we find that some classes of alternative models may be in tension with the inferred w(z) behaviour.PACS numbers: 98.80. Es, 98.80.Jk, 95.30.Sf

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Theoretical Models of Dark Energy

Cited by 218 publications

References 108 publications

On the Phenomenology of an Accelerated Large-Scale Universe

On the Phenomenology of an Accelerated Large-Scale Universe

Running vacuum cosmological models: linear scalar perturbations

New constraints on the dark energy equation of state

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