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We study mimetic $F(R)$ gravity with potential and Lagrange multiplier constraint. In the context of these theories, we introduce a reconstruction technique which enables us to realize arbitrary cosmologies, given the Hubble rate and an…

General Relativity and Quantum Cosmology · Physics 2016-02-17 S. D. Odintsov , V. K. Oikonomou

In this study, we explore the mimetic matter model proposed by Chamseddine and Mukhanov (J. High Energy Phys. 11, 135, 2013), utilizing the holographic principle to coherently describe both the early and late universe when bulk viscosity is…

General Relativity and Quantum Cosmology · Physics 2024-12-03 G. S Khadekar Saibal Ray Aritra Sanyal

We deal with quadratic metric-affine gravity (QMAG), which is an alternative theory of gravity and present a new explicit representation of the field equations of this theory. In our previous work we found new explicit vacuum solutions of…

General Relativity and Quantum Cosmology · Physics 2017-06-01 Vedad Pasic , Elvis Barakovic , Nermin Okicic

A general formalism to find the density profile of a slowly rotating stellar object in modified gravity is presented. We derive a generic Lane-Emden equation and its analytical solution for a wide class of modified theories of gravity.

General Relativity and Quantum Cosmology · Physics 2022-12-23 Shaswata Chowdhury , Pritam Banerjee , Aneta Wojnar

One of the most important achievements in general relativity has been discovery of the $(2+1)$-dimensional black hole solutions of Einstein gravity in anti-de Sitter (AdS) spacetime [Phys. Rev. Lett. {\bf69}, 1849 (1992)]. In this paper, we…

General Relativity and Quantum Cosmology · Physics 2021-02-12 Ahmad Sheykhi

We address neutron stars and black holes in alternative gravities, after recalling their basic properties in General Relativity. Among the plethora of interesting alternative gravities we here focus on an interesting set of scalar-tensor…

General Relativity and Quantum Cosmology · Physics 2022-04-12 Jose Luis Blázquez-Salcedo , Burkhard Kleihaus , Jutta Kunz

The modified Lane-Emden equation for stellar hydrostatic equilibrium in f(R)-gravity is numerically solved by using an iterative procedure. Such an integro-differential equation can be obtained in the weak field limit approximation of…

Solar and Stellar Astrophysics · Physics 2015-06-17 R. Farinelli , M. De Laurentis , S. Capozziello , S. D. Odintsov

This work provides a short but comprehensible overview of some relevant aspects of metric-affine theories of gravity in relation to the physics and astrophysics of compact objects. We shall highlight the pertinence of this approach to…

General Relativity and Quantum Cosmology · Physics 2020-08-26 Diego Rubiera-Garcia

In the present work, we obtain the hydrostatic equilibrium configurations of neutron stars in the recently proposed $f(R,\mathcal{L},T)$ theory of gravity, for which $R$ is the Ricci scalar, $\mathcal{L}$ is the matter lagrangian density,…

General Relativity and Quantum Cosmology · Physics 2024-02-26 J. A. S. Fortunato , P. H. R. S. Moraes , E. Brito , J. G. de Lima Júnior , T. S. Guerini

Recently, the phenomenology of f(R) gravity has been scrutinized motivated by the possibility to account for the self-accelerated cosmic expansion without invoking dark energy sources. Besides, this kind of modified gravity is capable of…

General Relativity and Quantum Cosmology · Physics 2015-08-28 Salvatore Capozziello , Tiberiu Harko , Tomi S. Koivisto , Francisco S. N. Lobo , Gonzalo J. Olmo

Mimetic gravity is a Weyl-symmetric extension of General Relativity, related to the latter by a singular disformal transformation, wherein the appearance of a dust-like perfect fluid can mimic cold dark matter at a cosmological level.…

General Relativity and Quantum Cosmology · Physics 2017-03-03 L. Sebastiani , S. Vagnozzi , R. Myrzakulov

In this article we try to present spherically symmetric isotropic strange star model under the framework of $f(R,\mathcal{T})$ theory of gravity. To this end, we consider that the Lagrangian density is an arbitrary linear function of the…

General Relativity and Quantum Cosmology · Physics 2018-04-23 Debabrata Deb , Farook Rahaman , Saibal Ray , B. K. Guha

Alternative gravity theory is currently an incredibly significant technique for addressing some enduring experimental difficulties, such as the universe's dark region. They may also be employed in celestial cosmology, producing results that…

General Relativity and Quantum Cosmology · Physics 2024-05-01 Tayyaba Naz , Adnan Malik , Zenab Ramay

We consider a special class of the tetrad theory of gravitation which can be considered as a viable alternative gravitational theories. We investigate cosmological models based on those theories by examining the possibility of fitting the…

General Relativity and Quantum Cosmology · Physics 2007-05-23 H. A. Alhendi , E. I. Lashin , G. L. Nashed

Modified gravity is one of the most promising candidates for explaining the current accelerating expansion of the Universe, and even its unification with the inflationary epoch. Nevertheless, the wide range of models capable to explain the…

General Relativity and Quantum Cosmology · Physics 2015-06-03 Álvaro de la Cruz-Dombriz , Diego Sáez-Gómez

Motivated by earlier works on reconstruction of modified gravity models with dark energy components, we extend them by considering a newly proposed model of (m, n)- type of holographic dark energy for two models of modified gravity, f(R)…

Cosmology and Nongalactic Astrophysics · Physics 2013-08-14 M. Umar Farooq , Mubasher Jamil , Davood Momeni , Ratbay Myrzakulov

We use a modified Einstein-Maxwell gravity to study stability of an electrostatic spherical star. Correction terms in this model are scalers which are made from contraction of Ricci tensor and electromagnetic vector potential. Our…

General Relativity and Quantum Cosmology · Physics 2023-12-05 Hossein Ghaffarnejad , Tohid Ghorbani , Firoozeh Eidizadeh

We consider the effect of a logarithmic f(R) theory, motivated by the form of the one-loop effective action arising from gluons in curved spacetime, on the structure of relativistic stars. In addition to analysing the consistency…

General Relativity and Quantum Cosmology · Physics 2013-12-16 Hamzeh Alavirad , Joel M. Weller

In this work, we investigate the existence of neutron stars (NS) in the framework of $f$($\mathbb{T}$,$\mathcal{T}$) gravity, where $\mathbb{T}$ is the torsion tensor and $\mathcal{T}$ is the trace of the energy-momentum tensor. The…

High Energy Astrophysical Phenomena · Physics 2023-01-11 Clésio E. Mota , Luis C. N. Santos , Franciele M. da Silva , Cesar V. Flores , Iarley P. Lobo , Valdir B. Bezerra

Extensions of the gravity theory in order to obtain traceless field equations have been widely considered in the literature. The leading example of such class of theories is the unimodular gravity, but there are other possibilities like the…

General Relativity and Quantum Cosmology · Physics 2019-12-23 Mahamadou Daouda , J. C. Fabris , A. M. Oliveira , F. Smirnov , H. E. S. Velten