Non-minimally coupled quintom model inspired by string theory

Sadeghi, J.; Setare, M. R.; Banijamali, A.; Milani, F.

doi:10.1016/j.physletb.2008.02.062

Cited by 84 publications

(35 citation statements)

References 60 publications

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“…In contrast to Refs. (Cai et al, 2007b;Sadeghi et al, 2008;Li et al, 2005) here we do not need to add an extra term or a dimension-6 operator ⊔ ⊓T ⊔ ⊓T in the Lagrangian of tachyon field.…”

Section: Resultsmentioning

confidence: 99%

“…In Refs. (Cai et al, 2007b;Sadeghi et al, 2008) the Authors have been added an extra higher derivative term T ⊔ ⊓T in the square root part of the tachyonic Lagrangian and showed that crossing of the phantom divide occurs before reaching the tachyon potential asymptotically to its minimum. Considering a spatially-flat Friedmann-Robertson-Walker (FRW) metric,…”

Section: The Modelmentioning

confidence: 99%

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Tachyonic teleparallel dark energy

Banijamali

Fazlpour

2012

Astrophys Space Sci

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Teleparallel gravity is an equivalent formulation of general relativity in which instead of the Ricci scalar R, one uses the torsion scalar T for the Lagrangian density. Recently teleparallel dark energy has been proposed by Geng et al. in (Geng et al., 2011). They have added quintessence scalar field, allowing also a non-minimal coupling with gravity in the Lagrangian of teleparallel gravity and found that such a non-minimally coupled quintessence theory has a richer structure than the same one in the frame work of general relativity. In the present work we are interested in tachyonic teleparallel dark energy in which scalar field is responsible for dark energy in the frame work of torsion gravity. We find that such a non-minimally coupled tachyon gravity can realize the crossing of the phantom divide line for the effective equation of state. Using the numerical calculations we display such a behavior of the model explicitly.

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Section: Resultsmentioning

confidence: 99%

Section: The Modelmentioning

confidence: 99%

Tachyonic teleparallel dark energy

Banijamali

Fazlpour

2012

Astrophys Space Sci

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“…Thus, one adds an extra term T 2T to the usual terms in the square root and the non-minimal coupling Rf (T ) [119,227]: where M p is the reduced Planck mass. Action (6.29) can be brought to a simpler form for the derivation of the equations of motion by performing a conformal transformation g µν → f (T )g µν :…”

Section: A Model Inspired By String Theorymentioning

confidence: 99%

Quintom cosmology: Theoretical implications and observations

et al. 2010

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We review the paradigm of quintom cosmology. This scenario is motivated by the observational indications that the equation of state of dark energy across the cosmological constant boundary is mildly favored, although the data are still far from being conclusive. As a theoretical setup we introduce a no-go theorem existing in quintom cosmology, and based on it we discuss the conditions for the equation of state of dark energy realizing the quintom scenario. The simplest quintom model can be achieved by introducing two scalar fields with one being quintessence and the other phantom. Based on the double-field quintom model we perform a detailed analysis of dark energy perturbations and we discuss their effects on current observations. This type of scenarios usually suffer from a manifest problem due to the existence of a ghost degree of freedom, and thus we review various alternative realizations of the quintom paradigm. The developments in particle physics and string theory provide potential clues indicating that a quintom scenario may be obtained from scalar systems with higher derivative terms, as well as from nonscalar systems. Additionally, we construct a quintom realization in the framework of braneworld cosmology, where the cosmic acceleration and the phantom divide crossing result from the combined effects of the field evolution on the brane and the competition between four and five dimensional gravity. Finally, we study the outsets and fates of a universe in quintom cosmology. In a scenario with null energy condition violation one may obtain a bouncing solution at early times and therefore avoid the Big Bang singularity. Furthermore, if this occurs periodically, we obtain a realization of an oscillating universe. Lastly, we comment on several open issues in quintom cosmology and their connection to future investigations.

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“…To this effect, a large variety of scalar field models are discussed in the literature including quintessence [8][9][10][11][12][13][14], K-essence [15,16], spintessence [17], a e-mail: mohdshahamu@gmail.com b e-mail: shibesh.math@gmail.com c e-mail: rmyrzakulov@gmail.com tachyon [18,19], quintom [20][21][22][23][24][25][26][27], chameleon [28][29][30][31] and many more. These models of the scalar field give the equation of state parameter w ≥ −1.…”

Section: Introductionmentioning

confidence: 99%

Galileons, phantom fields, and the fate of the Universe

2016

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In this paper we study cosmological dynamics of the phantom as well as non-phantom fields with a linear potential in the presence of a Galileon correction (∂ μ φ∂ μ φ) φ. We show that the Big Crunch singularity is delayed compared to the standard case; the delay crucially depends upon the strength of a Galileon correction. As for the phantom Galileon, ρ φ is shown to grow more slowly compared to the standard phantom delaying the approach of the singularity. In the case, V ∼ φ n , n > 4, Big Rip is also delayed, similar phenomenon is shown to take place for potentials steeper than the exponential.

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Non-minimally coupled quintom model inspired by string theory

Cited by 84 publications

References 60 publications

Tachyonic teleparallel dark energy

Tachyonic teleparallel dark energy

Quintom cosmology: Theoretical implications and observations

Galileons, phantom fields, and the fate of the Universe

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