Mimetic covariant renormalizable gravity

Myrzakulov, Ratbay; Sebastiani, Lorenzo; Vagnozzi, Sunny; Zerbini, Sergio

doi:10.48550/arxiv.1505.03115

Cited by 13 publications

(19 citation statements)

References 18 publications

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“…where event horizon r = r h is the positive solution of equation f (r h ) = 0, which satisfies f ′ (r h ) = 0. The entropy is given by [88,89] (39), which indicates that we have negative values of T h when r h < r d and when r h > r d , T h becomes positive and (e) the heat capacity, (41), indicates that we obtain a positive heat capacity when r h < r d which indicates that the BH is stable.…”

Section: A Thermodynamics Of the Bh(19)mentioning

confidence: 99%

“…Equation (41) shows that H h does not locally diverge and that the BH exhibits a phase transition of the second order. The heat capacity is depicted in Figure 4 (e) which also shows that H h < 0 when µ = −1 for different values of charge parameter q.…”

Section: A Thermodynamics Of the Bh(19)mentioning

confidence: 99%

“…The expression of mimetic gravity was first introduced in [20], and many studies on mimetic gravity under different topics have since been carried out [25,26]. An extension of mimetic gravitational theory to f (R) theory has been formulated [27][28][29][30][31][32][33][34][35] and many cosmological applications of mimetic gravitational theory have been conducted [36][37][38][39][40][41][42]. Moreover, several astrophysical black hole (BH) solutions in mimetic theory are discussed in Refs.…”

Section: Introductionmentioning

confidence: 99%

“…Schematic plots of the thermodynamic quantities of the BH solution (19) for the negative value of parameter µ: (a) typical behavior of metric function f (r) obtained using Eq. (34); (b) the mass-radius relation of the horizon (35); (c) typical behavior of the entropy of the horizon which indicates that S h increases quadratically as r h increases to always afford a positive entropy; (d) typical behavior of the temperature of horizon(39), which indicates that we have negative values of T h when r h < r d and when r h > r d , T h becomes positive and (e) the heat capacity,(41), indicates that we obtain a positive heat capacity when r h < r d which indicates that the BH is stable.…”

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Mimetic Euler-Heisenberg theory, charged solutions and multi-horizon black holes

Nashed,

Nojiri

2021

Preprint

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We construct several new classes of black hole (BH) solutions in the context of the mimetic Euler-Heisenberg theory. We separately derive three differently charged BH solutions and their relevant mimetic forms. We show that the asymptotic form of all BH solutions behaves like a flat spacetime. These BHs, either with/without cosmological constant, have the non constant Ricci scalar, due to the contribution of the Euler-Heisenberg parameter, which means that they are not solution to standard or mimetic f (R) gravitational theory without the Euler-Heisenberg non-linear electrodynamics and at the same time they are not equivalent to the solutions of the Einstein gravity with a massless scalar field. Moreover, we display that the effect of the Euler-Heisenberg theory makes the singularity of BH solutions stronger compared with that of BH solutions in general relativity. Furthermore, we show that the null and strong energy conditions of those BH solutions are violated, which is a general trend of mimetic gravitational theory. The thermodynamics of the BH solutions are satisfactory although there appears a negative Hawking temperature under some conditions. Additionally, these BHs obey the first law of thermodynamics. We also study the stability, using the geodesic deviation, and derive the stability condition analytically and graphically. Finally, for the first time and under some conditions, we derived multi-horizon BH solutions in the context of the mimetic Euler-Heisenberg theory and study their related physics.

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Section: A Thermodynamics Of the Bh(19)mentioning

confidence: 99%

Section: A Thermodynamics Of the Bh(19)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Mimetic Euler-Heisenberg theory, charged solutions and multi-horizon black holes

Nashed,

Nojiri

2021

Preprint

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“…In order to provide a unified description of dark energy and dark matter through a simple scalar field one can use different extensions of the canonical scalar field action [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. Ref.…”

Section: Introductionmentioning

confidence: 99%

$Λ$CDM as a Noether Symmetry in Cosmology

Benisty,

Guendelman,

Nissimov

et al. 2020

Preprint

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The standard ΛCDM model of cosmology is formulated as a simple modified gravity coupled to a single scalar field ("darkon") possessing a non-trivial hidden nonlinear Noether symmetry. The main ingredient in the construction is the use of the formalism of non-Riemannian spacetime volumeelements. The associated Noether conserved current produces stress-energy tensor consisting of two additive parts -dynamically generated dark energy and dark matter components non-interacting among themselves. Noether symmetry breaking via an additional scalar "darkon" potential introduces naturally an interaction between dark energy and dark matter. The correspondence between the ΛCDM model and the present "darkon" Noether symmetry is exhibited up to linear order w.r.t. gravity-matter perturbations. By breaking the Noether symmetry we obtain H0 = 69.18±4.293 and σ8 = 0.7860 ± 0.1106 from combined data of the direct measurements of the Hubble expansion and growth of matter results, which is closer to latest PLANCK results.

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Unimodular-mimetic cosmology

Nojiri

Odintsov

Oikonomou

2016

Class. Quantum Grav.

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We combine the unimodular gravity and mimetic gravity theories into a unified theoretical framework, which is proposed to provide a suggestive proposal for a framework that may assist in the discussion and solution search of the cosmological constant problem and of the dark matter issue. After providing the formulation of the unimodular mimetic gravity and investigating all the new features that the vacuum unimodular gravity implies, by using the underlying reconstruction method, we realize some well known cosmological evolutions, with some of these being exotic for the ordinary Einstein-Hilbert gravity. Specifically we provide the vacuum unimodular mimetic gravity description of the de Sitter cosmology and of the perfect fluid with constant equation of state cosmology. As we demonstrate, these cosmologies can be realized by vacuum mimetic unimodular gravity, without the existence of any matter fluid source. Moreover, we investigate how cosmologically viable cosmologies, which are compatible with the recent observational data, can be realized by the vacuum unimodular mimetic gravity. Since in some cases, the graceful exit from inflation problem might exist, we provide a qualitative description of the mechanism that can potentially generate the graceful exit from inflation in these theories, by searching for the unstable de Sitter solutions in the context of unimodular mimetic theories of gravity.

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Mimetic covariant renormalizable gravity

Cited by 13 publications

References 18 publications

Mimetic Euler-Heisenberg theory, charged solutions and multi-horizon black holes

Mimetic Euler-Heisenberg theory, charged solutions and multi-horizon black holes

$Λ$CDM as a Noether Symmetry in Cosmology

Unimodular-mimetic cosmology

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