Aspects of axion F(R) gravity

Odintsov, Sergei D.; Oikonomou, V. K.

doi:10.1209/0295-5075/129/40001

Cited by 54 publications

(21 citation statements)

References 152 publications

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“…Some of the higher curvature models which are well known to provide such a unified description of early and late-time acceleration can be found in Refs. [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] in the context of FðRÞ gravity, [66][67][68][69][70][71][72][73][74][75][76][77][78] in the fðR; GÞ gravity, etc. Recently, the axion-FðRÞ gravity model was proposed in [55,61], where the axion field mimics the dark matter evolution and hence the model provides a description of dark matter along with the unification of early and late-time acceleration eras.…”

Section: Introductionmentioning

confidence: 99%

Unifying holographic inflation with holographic dark energy: A covariant approach

et al. 2020

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In the present paper, we use the holographic approach to describe the early-time acceleration and the late-time acceleration eras of our Universe in a unified manner. Such "holographic unification" is found to have a correspondence with various higher curvature cosmological models with or without matter fields. The corresponding holographic cutoffs are determined in terms of the particle horizon and its derivatives, or the future horizon and its derivatives. As a result, the holographic energy density we propose is able to merge various cosmological epochs of the Universe from a holographic point of view. We find the holographic correspondence of several FðRÞ gravity models, including axion-FðRÞ gravity models, of several Gauss-Bonnet FðGÞ models and finally of FðTÞ models, and in each case we demonstrate that it is possible to describe in a unified way inflation and late-time acceleration in the context of the same holographic model.

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Section: Introductionmentioning

confidence: 99%

Unifying holographic inflation with holographic dark energy: A covariant approach

et al. 2020

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“…While the standard approach is to introduce some potential with slow-roll behavior, a successful model of quintessential inflation can be obtained from the ansatz of the slow-roll parameter as a function of the scale parameter itself (or the number of e-folds) [77][78][79], especially, with a Lorentzian ansatz [1]. Here we calculate the complete evolution of the universe from this ansatz.…”

Section: Introductionmentioning

confidence: 99%

Quintessential inflation from Lorentzian slow roll

Benisty

Guendelman

2020

Eur. Phys. J. C

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From the assumption that the slow-roll parameter ε has a Lorentzian form as a function of the e-fold number N , a successful model of a quintessential inflation is obtained, as succinctly studied in [1]. The form corresponds to the vacuum energy both in the inflationary and in the dark-energy epochs and satisfies the condition to climb from small values of ε to 1 at the end of the inflationary epoch. We find the corresponding scalar quintessential inflationary potential with two flat regions. Moreover, a reheating mechanism is suggested with numerical estimation for the homogeneous evolution of the universe. The suggested mechanism is consistent with the BBN bound.

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“…To date, there are two main ways to describe the inflationary era, with the first being by using the single scalar field description [1][2][3], while the other is by using the modified gravity description [4][5][6][7][8][9]. Both ways are appealing, however the modified gravity description is somewhat more complete since it offers the appealing possibility of describing the inflationary and the dark energy era by using the same theoretical framework [10][11][12][13]. Of course we need also to mention that bouncing cosmology is an also quite appealing alternative to inflation [14].…”

Section: Introductionmentioning

confidence: 99%

$k$-Inflation-corrected Einstein-Gauss-Bonnet Gravity with Massless Primordial Gravitons

Odintsov,

Oikonomou,

Fronimos

2021

Preprint

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In the present paper, we study the inflationary phenomenology of a k-inflation corrected Einstein-Gauss-Bonnet theory. Non-canonical kinetic terms are known for producing Jean instabilities or superluminal sound wave velocities in the aforementioned era, but we demonstrate in this work that by adding Gauss-Bonnet string corrections and assuming that the non-canonical kinetic term ωX γ is in quadratic, one can obtain a ghost free description. Demanding compatibility with the recent GW170817 event forces one to accept that the relation ξ = H ξ for the scalar coupling function ξ(φ). As a result, the scalar functions of the theory are revealed to be interconnected and by assuming a specific form for one of them, specifies immediately the other. Here, we shall assume that the scalar potential is directly derivable from the equations of motion, once the Gauss-Bonnet coupling is appropriately chosen, but obviously the opposite is feasible as well. As a result, each term entering the equations of motion, can be written in terms of the scalar field and a relatively tractable phenomenology is produced. For quadratic kinetic terms, the resulting scalar potential is quite elegant functionally. Different exponents, which lead to either a more perplexed solution for the scalar potential, are still a possibility which was not further studied. We also discuss in brief the non-Gaussianities issue under the slow-roll and constant-roll conditions holding true, and we demonstrate that the predicted amount of non-Gaussianities is significantly enhanced in comparison to the k-inflation free Einstein-Gauss-Bonnet theory.

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Aspects of axion F(R) gravity

Cited by 54 publications

References 152 publications

Unifying holographic inflation with holographic dark energy: A covariant approach

Unifying holographic inflation with holographic dark energy: A covariant approach

Quintessential inflation from Lorentzian slow roll

$k$-Inflation-corrected Einstein-Gauss-Bonnet Gravity with Massless Primordial Gravitons

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