On Stability of Asymptotically Free Mimetic Hořava Gravity

Russ, Tobias B.

doi:10.48550/arxiv.2103.12442

Cited by 3 publications

(3 citation statements)

References 33 publications

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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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“…It has also been shown that this theory can explain the flat rotation curves of spiral galaxies without needing to particles DM [10,11]. Mimetic theory of gravity has arisen a lot of enthusiasm in the past few years both from the cosmological viewpoint [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] as well as black holes physics [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. The investigations on the mimetic theory of gravity were also generalized to f (R) gravity [51][52][53][54][55][56][57][5...…”

Section: Introductionmentioning

confidence: 99%

Structure formation in mimetic gravity

Farsi¹,

Sheykhi²

2022

Preprint

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Mimetic theory of gravity was proposed as an alternative description for the dark matter (DM) puzzle. It was argued that the mimetic field can encode a dynamical longitudinal degree of freedom which can play the role of mimetic DM. In this paper, we disclose the effects of an extra longitudinal degree of freedom on the evolution of perturbations in the framework of mimetic gravity. We consider a flat Friedmann-Robertson-Walker (FRW) background and explore the linear perturbations by adopting the spherically symmetric collapse formalism. By suitably choosing the potential of the mimetic field, we are able to solve the perturbed field equations in the linear regime and derive the density contrast δm in terms of the redshift parameter z. We observe that δm starts growing from its initial value at the early stages of the universe and as the universe expands, it grows slower compared to the standard cosmology. This may due to the extra degree of freedom of the gravitational field which affects the growth of perturbations. We then consider the effects of this potential on the density abundance and the deceleration parameter. We find out that mimetic potential can play the role of dark energy (DE) and affects the dynamics of matter perturbations and cosmological parameters.

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“…Furthermore, it has been demonstrated that mimetic theory can explore the coherent rotational patterns observed in spiral galaxies without relying on the existence of dark matter particles [13,14]. Lately, there has been a significant surge of enthusiasm surrounding the cosmological framework due to the emergence of the mimetic theory [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] and black holes physics [33][34][35][36][37][38][39][40][41][42][43][44][45][45][46][47][48][49][50][51]. The theory has further extended its scope to include f (R) mimetic gravity, incorporating additional insights and explanations [52][53][54][55][56][57][58][59]…”

Section: Introductionmentioning

confidence: 99%

Black holes with Lagrange multiplier and potential in mimetic-like gravitational theory: multi-horizon black holes

Nashed

Nojiri

2022

J. Cosmol. Astropart. Phys.

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In this paper, we consider the mimetic-like field equations coupled with the Lagrange multiplier and the potential to derive non-trivial spherically symmetric black hole (BH) solutions. We divided this study into three cases: in the first one, we choose the Lagrange multiplier and the potential to vanish and derive a BH solution that coincides with the BH of the Einstein general relativity despite the non-vanishing value of the mimetic-like scalar field. The first case is consistent with the previous studies in the literature where the mimetic theory coincides with GR [1]. In the second case, we derive a solution with a constant value of the potential and a dynamical value of the Lagrange multiplier. This solution has no horizon, and therefore, the obtained space-time does not correspond to the BH. In this solution, there appears a region of the Euclidian signature where the signature of the diagonal components of the metric is (+,+,+,+) or the region with two times where the signature is (+,+,-,-). Finally, we derive a BH solution with non-vanishing values of the Lagrange multiplier, potential, and mimetic-like scalar field. This BH shows a soft singularity compared with the Einstein BH solution. The relevant physics of the third case is discussed by showing their behavior of the metric potential at infinity, calculating their energy conditions, and studying their thermodynamical quantities. We give a brief discussion on how our third case can generate a BH with three horizons as in the de Sitter-Reissner-Nordström black hole space-time, where the largest horizon is the cosmological one and two correspond to the outer and inner horizons of the BH. Even in the third case, the region of the Euclidian signature or the region with two times appears. We give a condition that such unphysical region(s) is hidden inside the black hole horizon and the existence of the region(s) becomes less unphysical. We also study the thermodynamics of the multi-horizon BH and consider the extremal case, where the radii of two horizons coincide with each other. We observe that the Hawking temperature and the heat capacity vanish in the extremal limit. Finally, we would like to stress the fact that in spite that the field equations we use have no cosmological constant, our BH solutions of the second and third case behave asymptotically as AdS/dS.

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On Stability of Asymptotically Free Mimetic Hořava Gravity

Cited by 3 publications

References 33 publications

Isotropic stellar model in mimetic theory

Isotropic stellar model in mimetic theory

Structure formation in mimetic gravity

Black holes with Lagrange multiplier and potential in mimetic-like gravitational theory: multi-horizon black holes

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