Inflationary universe in 
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 gravity with antisymmetric tensor fields and their suppression during its evolution

Elizalde, E.; Odintsov, Sergei D.; Paul, Tanmoy; Sáez-Gómez, Diego

doi:10.1103/physrevd.99.063506

Cited by 75 publications

(49 citation statements)

References 76 publications

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“…Such inconsistency of the spectral index in the context of a matter bounce scenario was also confirmed in [70] from a slightly different point of view, namely from an F(R) theory of gravity. F(R) models can be equivalently mapped to scalar-tensor ones via conformal transformation of the metric [75][76][77] and, thus, the inconsistencies of the spectral index from two different models are well justified. Secondly, according to the Planck 2018 data, the running of the spectral index is constrained to be −0.0085 ± 0.0073.…”

Section: Introductionmentioning

confidence: 99%

Viable non-singular cosmic bounce in holonomy improved F(R) gravity endowed with a Lagrange multiplier

2020

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Matter and quasi-matter bounce scenarios are studied for an F(R) gravity model with holonomy corrections and a Lagrange multiplier, with a scale factor a(t) = a0t 2 + 1 n , where the Hubble parameter squared has a linear and a quadratic dependence on the effective energy density. Provided n < 1/2, it is shown that the primordial curvature perturbations are generated deeply into the contracting era, at large negative time, which makes the low-curvature limit a good approximation for calculating the perturbation power spectrum. Moreover, it is shown that, for n within this range, the obtained cosmological quantities are fully compatible with the Planck constraints, and that the "low curvature limit" comes as a viable approximation to calculate the power spectra of both scalar and tensor perturbations. Using reconstruction techniques for F(R) gravity with the Lagrange multiplier, the precise form of the effective F(R) gravity is found, from which one determines the power spectra of scalar and tensor perturbations in such bouncing scenario. Correspondingly, the spectral index for curvature perturbations and the tensor to scalar ratio are obtained, and these values are successfully confronted with the latest Planck observations. Further, it is shown that both the weak and the null energy conditions are satisfied, thanks to the holonomy corrections performed in the theory-which are then proven to be necessary for achieving this goal. In fact, when approaching the bouncing era, the holonomy corrections become significant and play a crucial role in order to restore the energy conditions. Summing up, a cosmological bouncing scenario with the scale factor above and fulfilling the energy conditions can be adequately described by the F(R) model with a Lagrange multiplier and holonomy corrections, which prove to be very important.

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Section: Introductionmentioning

confidence: 99%

Viable non-singular cosmic bounce in holonomy improved F(R) gravity endowed with a Lagrange multiplier

2020

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“…Last but not the least, regarding our present work, the effects of rainbow functions on the structure of compact objects are also worth investigating, see e.g. [65,66]. More interestingly, in a framework of gravity's rainbow, we may extend the present work by studying the late-time evolution.…”

Section: Discussionmentioning

confidence: 71%

Inflation from f(R) theories in gravity’s rainbow

Areef

Channuie

2020

Eur. Phys. J. C

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In this work, we study the f (R) models of inflation in the context of gravity's rainbow theory. We choose three types of f (R) models: f (R) = R + α(R/M) n , f (R) = R + α R 2 + β R 2 log(R/M 2) and the Einstein-Hu-Sawicki model with n, α, β being arbitrary real constants. Here R and M are the Ricci scalar and mass scale, respectively. For all models, the rainbow function is written in the power-law form of the Hubble parameter. We present a detailed derivation of the spectral index of curvature perturbation and the tensor-to-scalar ratio and compare the predictions of our results with the latest Planck 2018 data. With the sizeable number of efoldings and proper choices of parameters, we discover that the predictions of all f (R) models present in this work are in excellent agreement with the Planck analysis.

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“…Motivated by these questions, we consider the Starobinsky + Kalb Ramond field model as the starting model. Thus the action we consider is given by [120],…”

Section: Cosmological Scenariomentioning

confidence: 99%

“…In both four and five dimensional spacetime, we employ non-dynamical (where the fields have no dynamics at all) and dynamical (where the fields have ceratin dynamics which can be obtained by the corresponding solutions in FRW spacetime) method respectively. It turns out that the 2nd rank Kalb-Ramond (KR) field has a significant contribution during early universe, in particular, it affects the beginning of inflation as well as increases the amount of primordial gravitational radiation [117,120,121,127]. However as the universe expands, the contribution of the KR field on the evolutionary process reduces significantly, and at present it almost does not affect the universe evolution.…”

Section: Introductionmentioning

confidence: 99%

Antisymmetric Tensor Fields in Modified Gravity: A Summary

Paul

2020

Symmetry

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We provide various aspects of second rank antisymmetric Kalb–Ramond (KR) field in modified theories of gravity. The KR field energy density is found to decrease with the expansion of our universe at a faster rate in comparison to radiation and matter components. Thus as the universe evolves and cools down, the contribution of the KR field on the evolutionary process reduces significantly, and at present it almost does not affect the universe evolution. However the KR field has a significant contribution during early universe; in particular, it affects the beginning of inflation as well as increases the amount of primordial gravitational radiation and hence enlarges the value of tensor-to-scalar ratio in respect to the case when the KR field is absent. In regard to the KR field couplings, it turns out that in four dimensional higher curvature inflationary model the couplings of the KR field to other matter fields is given by 1/MPl (where MPl is known as the “reduced Planck mass” defined by MPl=18πG with G is the “Newton’s constant”) i.e., same as the usual gravity–matter coupling; however in the context of higher dimensional higher curvature model the KR couplings get an additional suppression over 1/MPl. Thus in comparison to the four dimensional model, the higher curvature braneworld scenario gives a better explanation of why the present universe carries practically no footprint of the Kalb–Ramond field. The higher curvature term in the higher dimensional gravitational action acts as a suitable stabilizing agent in the dynamical stabilization mechanism of the extra dimensional modulus field from the perspective of effective on-brane theory. Based on the evolution of KR field, one intriguing question can be—“sitting in present day universe, how do we confirm the existence of the Kalb–Ramond field which has considerably low energy density (with respect to the other components) in our present universe but has a significant impact during early universe?” We try to answer this question by the phenomena “cosmological quantum entanglement” which indeed carries the information of early universe. Finally, we briefly discuss some future perspectives of Kalb–Ramond cosmology at the end of the paper.

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Inflationary universe in F(R) gravity with antisymmetric tensor fields and their suppression during its evolution

Cited by 75 publications

References 76 publications

Viable non-singular cosmic bounce in holonomy improved F(R) gravity endowed with a Lagrange multiplier

Viable non-singular cosmic bounce in holonomy improved F(R) gravity endowed with a Lagrange multiplier

Inflation from f(R) theories in gravity’s rainbow

Antisymmetric Tensor Fields in Modified Gravity: A Summary

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