Structure formation in mimetic gravity

Farsi, Bita; Sheykhi, Ahmad

doi:10.48550/arxiv.2202.04118

Cited by 3 publications

(3 citation statements)

References 70 publications

(80 reference statements)

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“…Moreover, mimetic theory can investigate the flat rotation curves of spiral galaxies without the need of dark matter [14,15]. From a cosmological point of view, the theory of mimetic has discussed a lot of interesting research papers in the past few years [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] and black holes physics [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53]. It has been shown that for a spherically symmetric spacetime the only solution is the Schwarzschild spacetime which means that the Birkhoff's theorem is hold.…”

Section: Introductionmentioning

confidence: 99%

Isotropic stellar model in mimetic theory

Nashed

2023

Gen Relativ Gravit

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We investigate how to derive an isotropic stellar model in the frame of mimetic gravitational theory. Recently, this theory has gained big interest due to its difference from Einstein’s general relativity (GR), especially in the domain non-vacuum solutions. In this regard, we apply the field equation of mimetic gravitational theory to a spherically symmetric ansatz and obtain an over determined system of non-linear differential equations in which the number of differential equations is less than the unknown functions. To overcome the over determined system we suppose a specific form of the temporal component of the metric potential, $$g_{tt}$$ g tt , and assume the vanishing of the anisotropic condition to derive the form of the spatial component of the metric, $$g_{rr}$$ g rr . In this regard, we discuss the possibility to derive a stellar isotropic model that is in agreement with observed pulsars. To examine the stability of the isotropic model we use the Tolman–Oppenheimer–Volkoff equation and the adiabatic index. Moreover, we test the model using a wide range of observed values of masses and radii of pulsars and show that they fit in a good way.

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Section: Introductionmentioning

confidence: 99%

Isotropic stellar model in mimetic theory

Nashed

2023

Gen Relativ Gravit

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“…An appropriate approach to investigate the growth of perturbations and structure formation is the so called Top-Hat Spherical Collapse (SC) model [3]. In this approach one considers a uniform and spherical symmetric perturbation in an expanding background and describes the growth of perturbations in a spherical region using the same Friedmann equations for the underlying theory of gravity [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Growth of Perturbations in Tsallis and Barrow Cosmology

Farsi¹,

Sheykhi²

2022

Preprint

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We disclose the effects of the entropic corrections to the Friedmann equations on the growth of perturbations in the early stages of the Universe. We consider two types of corrections to the area law of entropy, known as Tsallis and Barrow entropies. Using these corrections to entropy, we derive the modified Friedmann equations and explore the growth of perturbations in a flat universe filled with dark energy (DE) and dark matter (DM). We employ the spherically symmetric collapse formalism and work in the liner regime for the perturbations. We first consider the constant equation of state (EoS) parameter for the DE and then extend our study to the variable EoS parameter for DE. Interstingly enough, we find out that the profile of density contrast quite differs from the standard cosmology. We observe that the growth rate of matter perturbations crucially depend on the values of Tsallis and Barrow parameters. With increasing the correction parameters to the entropy, the total density contrast increases as well. This implies that perturbations grow up faster in a universe with modified entropy corrected Friedmann equations.

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“…An appropriate approach for investigating the growth of perturbations and structure formation is the so-called top-hat spherical collapse (SC) model [3]. In this approach, one considers a uniform and spherically symmetric perturbation in an expanding background and describes the growth of perturbations in a spherical region using the same Friedmann equations for the underlying theory of gravity [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Growth of perturbations in Tsallis and Barrow cosmology

Farsi

Sheykhi

2022

Eur. Phys. J. C

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We report the effects of entropic corrections to the Friedmann equations on the growth of perturbations in the early stages of the universe. We consider two types of corrections to the area law of entropy, known as Tsallis and Barrow entropy. Using these corrections to entropy, we derive the modified Friedmann equations and explore the growth of perturbations in a flat universe filled with dark matter (DM) and the cosmological constant. We employ the spherically symmetric collapse formalism and work in the linear regime for the perturbations. Interestingly enough, we find that the profile of density contrast is quite different from the standard cosmology in Tsallis and Barrow cosmology. We observe that the growth rate of matter perturbations crucially depends on the values of Tsallis and Barrow parameters. By increasing these entropy correction parameters, the total density contrast increases as well. This implies that perturbations grow faster in a universe with modified entropy-corrected Friedmann equations.

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Structure formation in mimetic gravity

Cited by 3 publications

References 70 publications

Isotropic stellar model in mimetic theory

Isotropic stellar model in mimetic theory

Growth of Perturbations in Tsallis and Barrow Cosmology

Growth of perturbations in Tsallis and Barrow cosmology

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