Chameleon field dynamics during inflation

Saba, Nasim; Farhoudi, Mehrdad

doi:10.1142/s0218271818500414

Cited by 17 publications

(26 citation statements)

References 113 publications

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“…This result can also be obtained by differentiating relation (55) with respect to time while using relation (30). Besides, relations (52) and (54) obviously show that definitions Q and X terms are exactly equal as expected, that is, the exchange of energy between geometry and the scalar field in the noncommutative model are the same as the exchange of energy between the matter and the scalar field in the chameleon model. Also, as Eq.…”

Section: Analogy Of the Modelssupporting

confidence: 63%

“…In this work, we study the effects of noncommutativity in the standard scalar-tensor model in which gravity is minimally coupled with a dynamical scalar field, and then, compare it with the chameleon mechanism while investigating an analogy between these two models. Actually, as a complementary to our previous work [52], such an analogy may provide a scenario to overcome the issue of the chameleon model during the inflationary epoch.…”

Section: Introductionmentioning

confidence: 73%

“…that can also be achieved by inserting relation (52) and result (57) into Eq. (35) while using relations (55) and (63).…”

Section: Analogy Of the Modelsmentioning

confidence: 99%

“…Moreover, as mentioned in Ref. [52], even in the limiting case, where the coupling strength in the exponential term of the conformal factor tends to zero (i.e., reducing to the minimal coupling case), still one can trace its effect in the corresponding Klein-Gordon equation. That is, it looks as if the ambient matter fluid somehow acts like an extra field and hence, it would have some effects during the chameleonic inflation.In this sense, encouraged by these issues, we have proposed in Ref.[52] that if the chameleon model, through some mechanism, reduces to the standard inflationary model during the inflation, then it may cover the whole era of the universe from the inflation up to the late time.…”

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confidence: 91%

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confidence: 91%

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Noncommutative universe and chameleon field dynamics

Saba

Farhoudi

2018

Annals of Physics

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We consider a noncommutative standard model with a minimal coupling scalar field and a dynamical deformation between the canonical momenta of its scale factor and scalar field, and a chameleon model with a non-minimally coupling scalar field. We indicate that there is a correspondence between these two models, more specific, actually between the noncommutative parameter and the chameleon coupling strength, and also between the matter density of the chameleon model and the noncommutative geometry. In addition, the analogy constrains the type of the matter field in the chameleon model to be nearly a cosmic string-like during the inflation. Thus, the scenario enables the evolution of the universe being described by one single scalar field. That is, the effects of the chameleon and the inflaton can be described by one single scalar field which plays the role of inflaton in the very early universe and then, acts as a chameleon field. Moreover, the proposed correspondence procedure not only sets some constraints on the noncommutative parameter and the chameleon coupling constant, but also nearly specifies functions of the scalar field and its potential.the quintessence models [44]- [49], provides a dynamical alternative to the static cosmological constant. Due to the coupling of the scalar and the matter fields with the gravitational strength, the chameleon field acquires a density-dependent mass and consequently, its property changes depending on the environmental situations. Because of such a dependence, its mass is very light in the cosmological scales, wherein it may play the role of dark energy and causes the cosmic late time acceleration. Although, in the regions of high density, such as on the earth, the chameleon field acquires a large mass that makes its effects being short-ranged and hence, becomes invisible in search for the EPviolation and fifth force in the current experimental and observational tests.However, in Refs. [50,51] by proving two theorems, it has been claimed that the effect of chameleonlike scalar fields is negligible on density perturbations considering the linear scales and also, its influence may not be regarded for the observed cosmic acceleration except as some form of dark energy. Also, in Ref.[52], we considered a coupling between the chameleon field and an unknown matter scalar field, and analyzed a possibility of an influence of the chameleon field on a cosmological acceleration of the universe inflation. In the context of the slow-roll approximations, by employing the potential usually used in this issue in the literature, we evaluated the number of e-folding of the model in order to verify its viability during the inflation. We examined the model for different ranges of the free parameters, however, the results of analysis showed that there is not much chance of having the viable chameleonic universe inflation. That is, as expected for the extreme case, the exponential term (entered due to the conformal factor describing the interaction of the chameleon field with an ambient matter)...

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Section: Analogy Of the Modelssupporting

confidence: 63%

Section: Introductionmentioning

confidence: 73%

“…that can also be achieved by inserting relation (52) and result (57) into Eq. (35) while using relations (55) and (63).…”

Section: Analogy Of the Modelsmentioning

confidence: 99%

mentioning

confidence: 91%

mentioning

confidence: 91%

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Noncommutative universe and chameleon field dynamics

Saba

Farhoudi

2018

Annals of Physics

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Phase‐space analysis of the anisotropies in Weyl integrable spacetime: Kantowski–Sachs cosmology

Paliathanasis

2023

Math Methods in App Sciences

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We consider anisotropic Kantowski–Sachs cosmology in Weyl integrable spacetime with an ideal gas. We perform a detailed analysis of the dynamics by investigating the stationary points and reconstruct the cosmological history. This analysis gives important information for the initial value problem in Weyl integrable spacetime. We study three cases, in which the scalar field mass depends only on the density of the ideal gas, with or without cosmological constant term, and when there exists an exponential scalar field potential. We conclude that the existence of the nonzero potential function is essential in order that a spatially flat FLRW universe which can describe inflation can be a future attractor.

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Chameleon Perfect Scalar Field as a Geometric Correction in $$\boldsymbol{f(R)}$$ Gravity

Parrilla,

Escamilla-Rivera

2023

Lecture Notes in Physics

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In this work, we derive the analytical form for a f(R) model that describes a perfect scalar field $$\phi $$ ϕ by assuming the existence of a chameleon mechanism. Based on four statements, at the background and perturbative level, it is possible to relate the extra terms from this theory as a geometrical perfect fluid term, whose has been expressed as possible candidates to explain the nature of the dark sector, and possibly, in the case of a perfect scalar chameleon during inflation, satisfy the big bang nucleosynthesis (BBN) constraints until late times.

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Chameleon field dynamics during inflation

Cited by 17 publications

References 113 publications

Noncommutative universe and chameleon field dynamics

Noncommutative universe and chameleon field dynamics

Phase‐space analysis of the anisotropies in Weyl integrable spacetime: Kantowski–Sachs cosmology

Chameleon Perfect Scalar Field as a Geometric Correction in $$\boldsymbol{f(R)}$$ Gravity

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