Modified gravity theories on a nutshell: Inflation, bounce and late-time evolution

Nojiri, Shin’ichi; Odintsov, Sergei D.; Oikonomou, V. K.

doi:10.1016/j.physrep.2017.06.001

Cited by 2,349 publications

(1,651 citation statements)

References 685 publications

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“…On th one hand these are motivated by their capability to explain the dynamics of self-gravitating systems and the accelerated expansion of the Universe without resorting to dark matter and/or dark energy [5][6][7][8][9][10][11][12][13][14]. On the other hand, they are also motivated by the fact that GR is not the quantum theory of gravity needed to describe the spacetime near the singularities, which, as is well known, seemingly cannot be avoided [15].…”

Section: Introductionmentioning

confidence: 99%

Kinetic theory of Jean instability in Eddington-inspired Born–Infeld gravity

Martino

Capolupo

2017

Eur. Phys. J. C

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We analyze the stability of self-gravitating systems which dynamics is investigated using the collisionless Boltzmann equation, and the modified Poisson equation of Eddington-inspired Born-Infield gravity. These equations provide a description of the Jeans paradigm used to determine the critical scale above which such systems collapse. At equilibrium, the systems are described using the time-independent Maxwell-Boltzmann distribution function f 0 (v). Considering small perturbations to this equilibrium state, we obtain a modified dispersion relation, and we find a new characteristic scale length. Our results indicate that the dynamics of self-gravitating astrophysical systems can be fully addressed in the Eddington-inspired Born-Infeld gravity. The latter modifies the Jeans instability in high densities environments, while its effects become negligible in star formation regions.

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Section: Introductionmentioning

confidence: 99%

Kinetic theory of Jean instability in Eddington-inspired Born–Infeld gravity

Martino

Capolupo

2017

Eur. Phys. J. C

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“…On the other hand, the recently proposed mimetic formulation is found to be able to generate non-trivial vacuum solutions [25]. When applied to Einstein-Hilbert action, the theory can explain the mysterious dark matter at the cosmological scale [25][26][27][28]. The vacuum, static, and spherically symmetric solutions of mimetic GR were also found in references [29][30][31].…”

Section: Introductionmentioning

confidence: 88%

The Mimetic Born-Infeld Gravity: The Primordial Cosmos and Spherically Symmetric Solutions

2017

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Abstract:The Eddington-inspired-Born-Infeld (EiBI) model is reformulated within the mimetic approach. In the presence of a mimetic field, the model contains non-trivial vacuum solutions. We study a realistic primordial vacuum universe and we prove the existence of regular solutions. Besides, the linear instabilities in the EiBI model are found to be avoidable for some bouncing solutions. For a vacuum, static and spherically symmetric geometry, a new branch of solutions in which the black hole singularity that is replaced with a lightlike singularity is found.

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“…Now, in search of the dark energy fluid, the cosmological constant Lambda, Λ, is considered to be the simplest and elegenat dark energy candidate due to its extreme support with the available astronomical data. However, inspite of its great success, the cosmological constant problem has been seriously investigated in the last several years which thus instigated cosmologists to look for alternative ways in the names of dynamical dark energy models [2], modified gravity theories [3,4,5,6,7,8,9]. In a similar fashion, time dependent Λ theory, where the equation of state for Lambda is pegged at '−1', has also been attracted in the current cosmological research.…”

Section: Introductionmentioning

confidence: 99%

Exact solutions, finite time singularities and non-singular universe models from a variety of Λ(t) cosmologies

Pan

2018

Mod. Phys. Lett. A

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Cosmological models with time dependent Λ (read as Λ(t)) have been investigated widely in the literature. Models that solve background dynamics analytically, are of special interest. Additionally, the allowance of past or future singularities at finite cosmic time in a specific model signals for a generic test on its viabilities with the current observations. Following these, in this work we consider a variety of Λ(t) models focusing on their evolutions and singular behaviour. We found that a series of models in this class can be exactly solved when the background universe is described by a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) line element. The solutions in terms of the scale factor of the FLRW universe offer different universe models, such as power law expansion, oscillating, and the singularity free universe as well. However, we also noticed that a large number of models in this series permits past or future cosmological singularities at finite cosmic time. At last we close the work with a note that the avoidance of future singularities is possible for certain models under some specific restrictions.PACS numbers: 98.80.-k, 95.36.+x

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Modified gravity theories on a nutshell: Inflation, bounce and late-time evolution

Cited by 2,349 publications

References 685 publications

Kinetic theory of Jean instability in Eddington-inspired Born–Infeld gravity

Kinetic theory of Jean instability in Eddington-inspired Born–Infeld gravity

The Mimetic Born-Infeld Gravity: The Primordial Cosmos and Spherically Symmetric Solutions

Exact solutions, finite time singularities and non-singular universe models from a variety of Λ(t) cosmologies

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