Dark Energy and the Accelerating Universe

Frieman, Joshua A.; Turner, Michael S.; Huterer, Dragan

doi:10.1146/annurev.astro.46.060407.145243

Cited by 1,638 publications

(1,409 citation statements)

References 179 publications

(152 reference statements)

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“…In the context of an accelerating Universe, it is argued by Usmani et al [1] that the equation of state of the kind p = −ρ may be related to the Λ-dark energy, an agent responsible for the second phase of the inflation of Hot Big Bang theory [13,14,15,16,17].…”

Section: Interior Space-timementioning

confidence: 99%

The (2+1)-dimensional gravastars

Rahaman¹,

Ray²,

Usmani³

et al. 2012

Physics Letters B

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We propose a new model of a gravastar in (2+1) anti-de Sitter space-time. This new three dimensional configuration has three different regions with different equations of state: [I] Interior: 0 ≤ r < r 1 , ρ = −p ; [II] Shell: r 1 ≤ r < r 2 , ρ = p; [III] Exterior: r 2 < r, ρ = p = 0. The outer region of this gravastar corresponds to the exterior (2 + 1) anti-de Sitter space-time, popularly known as the BTZ spacetime. Like BTZ model, Λ is taken to be negative, which at the junction turns out to be positive as required by stability of gravastar and mathematical consistency. After investigating the Interior space-time, Shell and Exterior space-time we have highlighted different physical features in terms of Length and Energy, Entropy, and Junction conditions of the spherical distribution. It is shown that the present model of charge-free gravastar in connection to the exterior (2+1) anti-de Sitter space-time or the BTZ space-time is non-singular.

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Section: Interior Space-timementioning

confidence: 99%

The (2+1)-dimensional gravastars

Rahaman¹,

Ray²,

Usmani³

et al. 2012

Physics Letters B

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“…The factor 2 in front of M is for later convenience, moreover, we will take M > 0 in view of its interpretation as a dynamically generated cosmological constant 1 . Indeed, taking into account (6), the expression (5) becomes:…”

Section: Gravity-matter Theory With a Non-riemannian Volume-form In Tmentioning

confidence: 99%

“…According to the standard cosmological model (Λ CDM model [1]- [3]) the energy density of the late time Universe is dominated by two "dark" components -around 70 % made out of "dark energy" [4]- [6] and around 25 % made out of "dark matter" [7]- [9]. Since more than a decade a principal challenge in modern cosmology is to understand theoretically from first principles the nature of both "dark" species of the universe's substance as a manifestation of the dynamics of a single entity of matter.…”

Section: Introductionmentioning

confidence: 99%

Metric-Independent Spacetime Volume-Forms and Dark Energy/Dark Matter Unification

Guendelman

Nissimov

Pacheva

2016

Springer Proceedings in Mathematics &Amp; Statistics

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The method of non-Riemannian (metric-independent) spacetime volumeforms (alternative generally-covariant integration measure densities) is applied to construct a modified model of gravity coupled to a single scalar field providing an explicit unification of dark energy (as a dynamically generated cosmological constant) and dust fluid dark matter flowing along geodesics as an exact sum of two separate terms in the scalar field energy-momentum tensor. The fundamental reason for the dark species unification is the presence of a non-Riemannian volume-form in the scalar field action which both triggers the dynamical generation of the cosmological constant as well as gives rise to a hidden nonlinear Noether symmetry underlying the dust dark matter fluid nature. Upon adding appropriate perturbation breaking the hidden "dust" Noether symmetry we preserve the geodesic flow property of the dark matter while we suggest a way to get growing dark energy in the present universe' epoch free of evolution pathologies. Also, an intrinsic relation between the above modified gravity + single scalar field model and a special quadratic purely kinetic "k-essence" model is established as a weak-versus-strong-coupling duality.

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“…Among the models that have been proposed as alternatives to the ΛCDM we can mention the dark energy (DE) [3], a fluid that fills all the space and has negative pressure. The source of this DE can be a scalar field as in quintessential models [4].…”

Section: Introductionmentioning

confidence: 99%

Asymmetry and dark energy evolution

Cárdenas

2018

J. Phys.: Conf. Ser.

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Abstract. The well known asymmetry of type Ia supernova data is used to infer general features of an alternative model for dark energy. Using a model that allows DE to vary with redshift as a probe, the results indicate the low redshift transition of the deceleration parameter q(z) is evident only taken data points from one hemisphere of the sky. A related effect is a reconstructed DE density X(z) that shows evolution (it decreases as redshift increases) only towards the hemisphere where q(z) manifest the transition. We discuss on possible theoretical frameworks where these effects can be explained.

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Dark Energy and the Accelerating Universe

Cited by 1,638 publications

References 179 publications

The (2+1)-dimensional gravastars

The (2+1)-dimensional gravastars

Metric-Independent Spacetime Volume-Forms and Dark Energy/Dark Matter Unification

Asymmetry and dark energy evolution

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