Unimodular-mimetic cosmology

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

doi:10.1088/0264-9381/33/12/125017

Cited by 59 publications

(63 citation statements)

References 69 publications

(253 reference statements)

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“…One can easily check that it is consistent with the equations (20) and (21). In terms of this equation and the constraint (24), we obtain the quadratic action after removing some surface terms, We can see from this quadratic action that there are no higher time derivative terms for γ ij and ζ, so there are still three propagating degrees of freedom in this model: two tensor degrees and one scalar degree.…”

Section: Possible Mimetic Model Without Instabilitiesmentioning

confidence: 59%

On (in)stabilities of perturbations in mimetic models with higher derivatives

Zheng

Shen

Mou

et al. 2017

J. Cosmol. Astropart. Phys.

103

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Usually when applying the mimetic model to the early universe, higher derivative terms are needed to promote the mimetic field to be dynamical. However such models suffer from the ghost and/or the gradient instabilities and simple extensions cannot cure this pathology. We point out in this paper that it is possible to overcome this difficulty by considering the direct couplings of the higher derivatives of the mimetic field to the curvature of the spacetime. PACS number(s): 98.80.-k * Electronic address: limz@ustc.edu.cn

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Section: Possible Mimetic Model Without Instabilitiesmentioning

confidence: 59%

On (in)stabilities of perturbations in mimetic models with higher derivatives

Zheng

Shen

Mou

et al. 2017

J. Cosmol. Astropart. Phys.

103

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“…6 In fact, Lagrange multipliers have been commonly used to enforce suitable constraints in quite a few cosmological studies or in the formulation of gravitational theories, for e.g. the 'dusty dark energy' models [188][189][190], some higher derivative gravity theories [191][192][193][194][195], and the mimetic gravity scenarios [196][197][198][199][200][201][202][203][204].…”

Section: Effective Scalar Field Mass Via Torsion Pseudo-tracementioning

confidence: 99%

Weakly dynamic dark energy via metric-scalar couplings with torsion

Sur¹,

Bhatia

2017

J. Cosmol. Astropart. Phys.

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Abstract. We study the dynamical aspects of dark energy in the context of a non-minimally coupled scalar field with curvature and torsion. Whereas the scalar field acts as the source of the trace mode of torsion, a suitable constraint on the torsion pseudo-trace provides a mass term for the scalar field in the effective action. In the equivalent scalar-tensor framework, we find explicit cosmological solutions representing dark energy in both Einstein and Jordan frames. We demand the dynamical evolution of the dark energy to be weak enough, so that the present-day values of the cosmological parameters could be estimated keeping them within the confidence limits set for the standard ΛCDM model from recent observations. For such estimates, we examine the variations of the effective matter density and the dark energy equation of state parameters over different redshift ranges. In spite of being weakly dynamic, the dark energy component differs significantly from the cosmological constant, both in characteristics and features, for e.g. it interacts with the cosmological (dust) fluid in the Einstein frame, and crosses the phantom barrier in the Jordan frame. We also obtain the upper bounds on the torsion mode parameters and the lower bound on the effective BransDicke parameter. The latter turns out to be fairly large, and in agreement with the local gravity constraints, which therefore come in support of our analysis.

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“…For more recent work concerning mimetic gravity see Refs. [5][6][7][8][11][12][13][17][18][19][20][21][22][23][24][25][26] or Ref.…”

Section: Introductionmentioning

confidence: 99%

Thick branes with inner structure in mimetic gravity

Zhong

Zhang

et al. 2018

Eur. Phys. J. C

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In this paper, thick branes generated by mimetic scalar field are investigated. Three typical thick brane models are constructed and the linear tensor and scalar perturbations are analyzed. These branes have different inner structures, some of which are absent in general relativity. For each brane model, the solution is stable under both tensor and scalar perturbations. The tensor zero modes are localized on the branes, while the scalar perturbations do not propagate and they are not localized on the brane. As the branes split into multi sub-branes for specific parameters, the potentials of the tensor perturbations also split into multi-wells, and this may lead to new phenomenon in the resonance of the tensor perturbation and the localization of matter fields.

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Unimodular-mimetic cosmology

Cited by 59 publications

References 69 publications

On (in)stabilities of perturbations in mimetic models with higher derivatives

On (in)stabilities of perturbations in mimetic models with higher derivatives

Weakly dynamic dark energy via metric-scalar couplings with torsion

Thick branes with inner structure in mimetic gravity

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