Why the measured cosmological constant is small

Rostami, T.; Jalalzadeh, S.

doi:10.1016/j.dark.2015.10.001

Cited by 8 publications

(7 citation statements)

References 64 publications

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“…In quantum physics this can be thought of as a type of zero-point-energy. However, observations suggest that ρ Λ ∼ 0.7ρ c putting an upper limit of the cosmological constant to be ∼ 10 −35 s −2 [47]. Nevertheless, the zero-point energy calculations of the quantum physics predict much larger value exceeds the upper limit by ∼ 120 orders of magnitude.…”

Section: De Sitter Cosmologymentioning

confidence: 99%

“…During the period Ω k = [−0.696, 0] the scalar field decays towards its minimum at the flat universe limit as Ω k (t f ) ∼ 0 with kinetic dominant universe. From (47) and (48), obviously the potential is negative as Ω k > 9−8π 9+8π ∼ −0.473, the universe may enter a recollapse phase. At the flat universe limit the positive and negative energies almost compensate each other.…”

Section: A the Closed Universementioning

confidence: 99%

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Reconstruction of f ( T ) $f(T)$ -gravity in the absence of matter

Hanafy¹,

Nashed²

2016

Astrophys Space Sci

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We derive an exact f (T ) gravity in the absence of ordinary matter in Friedmann-RobertsonWalker (FRW) universe, where T is the teleparallel torsion scalar. We show that vanishing of the energy-momentum tensor T µν of matter does not imply vanishing of the teleparallel torsion scalar, in contrast to general relativity, where the Ricci scalar vanishes. The theory provides an exponential (inflationary) scale factor independent of the choice of the sectional curvature. In addition, the obtained f (T ) acts just like cosmological constant in the flat space model. Nevertheless, it is dynamical in non-flat models. In particular, the open universe provides a decaying pattern of the f (T ) contributing directly to solve the fine-tuning problem of the cosmological constant. The equation of state (EoS) of the torsion vacuum fluid has been studied in positive and negative Hubble regimes. We study the case when the torsion is made of a scalar field (tlaplon) which acts as torsion potential. This treatment enables to induce a tlaplon field sensitive to the symmetry of the spacetime in addition to the reconstruction of its effective potential from the f (T ) theory. The theory provides six different versions of inflationary models. The real solutions are mainly quadratic, the complex solutions, remarkably, provide Higgs-like potential.PACS numbers: 98.80.Qc, 04.20.Cv, 98.80.Cq.

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Section: De Sitter Cosmologymentioning

confidence: 99%

Section: A the Closed Universementioning

confidence: 99%

Reconstruction of f ( T ) $f(T)$ -gravity in the absence of matter

Hanafy¹,

Nashed²

2016

Astrophys Space Sci

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“…For other extensions of Wesson's theory that have assumed an arbitrary number of noncompact extra dimensions, see [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Noncompactified Kaluza–Klein Gravity

2022

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We present a brief description of noncompactified higher-dimensional theories from the perspective of general relativity. More concretely, the Space–Time–Matter theory, or Induced Matter theory, and the reduction procedure used to construct the modified Brans–Dicke theory and the modified Sáez–Ballester theory are briefly explained. Finally, we apply the latter to the Friedmann–Lemaître–Robertson–Walker (FLRW) cosmological models in arbitrary dimensions and analyze the corresponding solutions.

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“…There exist several proposals which explain the origin of dark energy such as cosmological constant, the expectation value of the vacuum ground state, which leads to the hierarchy problem. 11 Modified theories of gravity such as f (R, T ), 12 DGP braneworld, 13 the extrinsic cosmology 14 where dark energy could actually be the manifestation of the local extrinsic shape of the spacetime, scalar-tensor theories, 15,16 modified matter models such as quintessence, 17, 18 K-essence, coupled dark energy 19 and dynamical dark energy models 20 are some examples. The simplest candidates to explain the dynamical dark energy are the minimal coupling scalar fields like as the quintessence and Phantom models.…”

Section: Introductionmentioning

confidence: 99%

Interacting dark side of universe through generalized uncertainty principle

Rashki

Fathi

Mostaghel

et al. 2019

Int. J. Mod. Phys. D

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We investigate the impact of the generalized uncertainty principle proposed by some approaches to quantum gravity such as string theory and doubly special relativity on the cosmology. Using generalized Poisson brackets, we obtain the modified Friedmann and Raychaudhuri equations and suggest a dynamical dark energy to explain the late time acceleration of the Universe. After considering the interaction between dark matter and dark energy, originated from the minimal length, we obtain the effective cosmological parameters and equation of state parameter for dark matter and dark energy. Finally, we show that the resulting model is equivalent to the Phantom and Tachyon fields.

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Why the measured cosmological constant is small

Cited by 8 publications

References 64 publications

Reconstruction of f ( T ) $f(T)$ -gravity in the absence of matter

Reconstruction of f ( T ) $f(T)$ -gravity in the absence of matter

Noncompactified Kaluza–Klein Gravity

Interacting dark side of universe through generalized uncertainty principle

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