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In this work we evaluate the physical acceptability of relativistic anisotropic spheres modeled by two polytropic equations of state -- with the same newtonian limit -- commonly used to describe compact objects in General Relativity. We…

General Relativity and Quantum Cosmology · Physics 2021-02-02 D. Suárez-Urango , L. A. Núñez , H. Hernández

We investigate anisotropic quark stars within the context of energy-momentum squared gravity (EMSG), assuming the internal composition consists of homogeneous, charge-neutral 3-flavor interacting quark matter with ${\cal O}(m_s^4)$…

General Relativity and Quantum Cosmology · Physics 2023-10-02 Qian Li , Xianming Liu , Ruijun Tang , Jiayong Xiao

We consider the Einstein-Maxwell system of equations in the context of isotropic coordinates for matter distributions with anisotropy in the presence of an electric field. We assume a polytropic equation of state for the matter…

General Relativity and Quantum Cosmology · Physics 2015-12-31 Sifiso A. Ngubelanga , Sunil D. Maharaj

Ibohal, Ishwarchandra and Singh proposed a class of exact, non-vacuum and conformally flat solutions of Einstein's equations whose stress tensor $T_{ab}$ has negative pressure. We show that $T_{ab}$ corresponds to an anisotropic fluid and…

General Relativity and Quantum Cosmology · Physics 2015-06-11 Hristu Culetu

We study a novel interacting dark energy $-$ dark matter scenario where the anisotropic stress of the large scale inhomogeneities is considered. The dark energy has a constant equation of state and the interaction model produces stable…

Cosmology and Nongalactic Astrophysics · Physics 2018-12-21 Weiqiang Yang , Supriya Pan , Lixin Xu , David F. Mota

We show that the dark energy effects can be modeled by using an \emph{Ising perfect fluid} with network interactions, whose low redshift equation of state, i.e. $\omega_0$, becomes $\omega_0=-1$ as in the $\Lambda$CDM model. In our picture,…

High Energy Physics - Theory · Physics 2015-06-15 Orlando Luongo , Damiano Tommasini

This paper examines the general formalism and applications of isotropic as well as anisotropic polytropic stars in curvature-matter coupled gravity. For this purpose, we consider static spherical and Schwarzschild spacetimes in the interior…

General Relativity and Quantum Cosmology · Physics 2022-02-16 M. Sharif , Amal Majid , M. Shafaqat

The influence of the anisotropy in the equilibrium and stability of strange stars is investigated through the numerical solution of the hydrostatic equilibrium equation and the radial oscillation equation, both modified from their original…

High Energy Astrophysical Phenomena · Physics 2017-06-30 José D. V. Arbañil , M. Malheiro

The equation of state characterizing the dark energy component is constrained by combining Chandra observations of the X-ray luminosity of galaxy clusters with independent measurements of the baryonic matter density and the latest…

Astrophysics · Physics 2008-11-26 J. A. S. Lima , J. V. Cunha , J. S. Alcaniz

In this paper, we study a triad of inhomogeneous scalar fields, known as "solid", as a source of homogeneous but anisotropic dark energy. By using a dynamical system approach, we find that anisotropic accelerated solutions can be realized…

General Relativity and Quantum Cosmology · Physics 2021-04-22 J. Motoa-Manzano , J. Bayron Orjuela-Quintana , Thiago S. Pereira , César A. Valenzuela-Toledo

This paper discusses a new model for galactic dark matter by combining an anisotropic pressure field corresponding to normal matter and a quintessence dark energy field having a characteristic parameter $\omega_q$ such that $-1<\omega_q<…

General Relativity and Quantum Cosmology · Physics 2011-07-15 F. Rahaman , Peter K. F. Kuhfittig , K. Chakraborty , M. Kalam , D. Hossain

We model a compact relativistic body with anisotropic pressures in the presence of an electric field. The equation of state is barotropic with a linear relationship between the radial pressure and the energy density. Simple exact models of…

General Relativity and Quantum Cosmology · Physics 2015-06-17 P. Mafa Takisa , S. D. Maharaj

We extend a known solution generating technique for isotropic fluids in order to construct more general models of anisotropic stars with poloidal magnetic fields. In particular, we discuss the magnetized versions of some well-known exact…

General Relativity and Quantum Cosmology · Physics 2018-06-06 Cristian Stelea , Marina-Aura Dariescu , Ciprian Dariescu

There are various cosmological models with polytropic equation of state associated to dark energy. Polytropic EoS has important applications in astrophysics, therefore a study of it on cosmological framework continues to be interesting.…

General Physics · Physics 2015-10-28 Martiros Khurshudyan

The properties of exotic stars are investigated. In particular, we study objects made entirely of dark matter and we take into account intrinsic anisotropies which have been ignored so far. We obtain exact analytical solutions to the…

General Relativity and Quantum Cosmology · Physics 2021-04-21 Pedro H. R. S. Moraes , Grigoris Panotopoulos , Ilidio Lopes

This paper presents a new wormhole solution by assuming that a homogeneously distributed fluid with equation of state $p=\omega\rho$ can be adapted to an anisotropic spacetime such as a wormhole and that this spacetime admits a…

General Relativity and Quantum Cosmology · Physics 2017-07-14 Peter K. F. Kuhfittig

General relativistic anisotropic fluid models whose fluid flow lines form a shear-free, irrotational, geodesic timelike congruence are examined. These models are of Petrov type D, and are assumed to have zero heat flux and an anisotropic…

General Relativity and Quantum Cosmology · Physics 2010-04-06 Des J. Mc Manus , Alan A. Coley

A generally anisotropic equation of state originally derived in the context of Newman-Janis rotating systems allows for vacuum energy at a specific density. In this paper we examine the possibility of using that equation of state for…

General Relativity and Quantum Cosmology · Physics 2023-09-08 Philip Beltracchi

Quasi-local variables, i.e. quantities whose values can be derived from physics accessible within an arbitrarily small neighborhood of a spacetime point, are used to construct the equation of state (EoS) for the anisotropic fluid in the…

General Relativity and Quantum Cosmology · Physics 2011-01-20 Dubravko Horvat , Sasa Ilijic , Anja Marunovic

A model for a flat homogeneous and isotropic Universe composed of dark energy, dark matter, neutrinos, radiation and baryons is analyzed. The fields of dark matter and neutrinos are supposed to interact with the dark energy. The dark energy…

General Relativity and Quantum Cosmology · Physics 2008-11-26 G. M. Kremer