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Polytropic stars are useful tools for learning about stellar structure without the complexity of comprehensive stellar models. These models rely on a certain power-law correlation between the star's pressure and density. This paper proposes…

General Relativity and Quantum Cosmology · Physics 2024-07-19 Akashdip Karmakar , Ujjal Debnath , Pramit Rej

We complete previous investigations on the thermodynamics of self-gravitating systems by studying the grand canonical, grand microcanonical and isobaric ensembles. We also discuss the stability of polytropic spheres in the light of a…

Astrophysics · Physics 2009-11-07 P. H. Chavanis

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

We study the structure of static spherical stars made up of a non-relativistic polytropic fluid in linearized higher-curvature theories of gravity (HCG). We first formulate the modified Lane-Emden (LE) equation for the stellar profile…

General Relativity and Quantum Cosmology · Physics 2023-07-26 Shinpei Tonosaki , Tomoya Tachinami , Yuuiti Sendouda

Filamentary molecular clouds are omnipresent in the cold interstellar medium. Observational evidences show that the non-isothermal equations of state describe the filaments properties better than the isothermal one. In this paper we use the…

Astrophysics of Galaxies · Physics 2021-02-04 Mohammad Mahdi Motiei , Mohammad Hosseinirad , Shahram Abbassi

We investigate static spherically symmetric perfect fluid models in Newtonian gravity for barotropic equations of state that are asymptotically polytropic at low and high pressures. This is done by casting the equations into a 3-dimensional…

Astrophysics · Physics 2009-11-07 J. Mark Heinzle , Claes Uggla

We discuss stability of spherically symmetric static solutions in Newtonian limit of Jordan, Brans-Dicke field equations. The behavior of the stable equilibrium solutions for the spherically symmetric configurations considered here, it…

General Relativity and Quantum Cosmology · Physics 2007-05-23 S. Kozyrev

The time evolution of initially balanced, rapidly rotating models for an isolated disk of highly flattened galaxies of stars is calculated. The method of direct integration of the Newtonian equations of motion of stars over a time span of…

Astrophysics · Physics 2007-05-23 Evgeny Griv , Michael Gedalin , Edward Liverts , David Eichler , Yehoshua Kimhi , Chi Yuan

The present work deals with a multi-field cosmological model in a spatially flat FLRW space-time geometry. The usual Brans-Dicke(BD) field and another scalar field are minimally coupled to gravity while they interact with each other through…

General Relativity and Quantum Cosmology · Physics 2024-07-10 Dipankar Laya , Sourav Dutta , Subenoy Chakraborty

The properties of filamentary interstellar clouds observed at sub-millimetre wavelengths, especially by the Herschel Space Observatory, are analysed with polytropic models in cylindrical symmetry. The observed radial density profiles are…

Solar and Stellar Astrophysics · Physics 2015-06-23 Claudia Toci , Daniele Galli

The aim of this paper is to perform stability analysis of anisotropic dissipative cylindrical collapsing model in $f(R,T,R_{\mu\nu} T^{\mu\nu})$ gravity. In this context, the modified version of hydrodynamical equation is explored by means…

General Relativity and Quantum Cosmology · Physics 2017-09-14 Z. Yousaf , M. Zaeem-ul-Haq Bhatti , Ume Farwa

The so-called "global polytropic model" is based on the assumption of hydrostatic equilibrium for the solar system, or for a planet's system of statellites (like the jovian system), described by the Lane-Emden differential equation. A…

Earth and Planetary Astrophysics · Physics 2014-10-14 Vassilis Geroyannis , Florendia Valvi , Themis Dallas

We utilise the phenomenologically parameterized piecewise polytropic equations of state to study various neutron star properties. We investigate the compliance of these equations of state with several astronomical observations. We also…

Nuclear Theory · Physics 2022-05-04 Jaikhomba Singha , S. Mullai Vaneshwar , Ankit Kumar

In this work, we generate two static anisotropic solutions for a sphere containing quark matter in the framework of self-interacting Brans-Dicke theory. For this purpose, we add an anisotropic source in the seed distribution and decouple…

General Relativity and Quantum Cosmology · Physics 2023-07-26 M. Sharif , Amal Majid

We consider the problem of building inhomogeneous cosmological models in scalar-tensor theories of gravity. This starts by splitting the field equations of these theories into constraint and evolution equations, and then proceeds by…

General Relativity and Quantum Cosmology · Physics 2019-09-04 Jessie Durk , Timothy Clifton

We consider slow-roll inflation in the context of a modified Brans-Dicke dilaton gravity. From a two self-interacting potentials $V(\phi)$, we reproduce a Starobinsky-like potential and, commonly in syperstring models, an exponential tail…

General Relativity and Quantum Cosmology · Physics 2024-11-11 Abraão J. S. Capistrano , Gilberto M. Kremer

We study the effects of magnetic fields of non-linear electrodynamics in chameleonic Brans-Dicke theory under the existence of anisotropic spherical fluid. In particular, we explore dissipative and non-dissipative self-gravitating systems…

General Relativity and Quantum Cosmology · Physics 2024-10-03 Z. Yousaf , M. Z. Bhatti , S. Rehman , Kazuharu Bamba

We study equilibrium states in relativistic galactic dynamics which are described by solutions of the Einstein-Vlasov system for collisionless matter. We recast the equations into a regular three-dimensional system of autonomous first order…

General Relativity and Quantum Cosmology · Physics 2019-05-01 Mikael Fjällborg , J. Mark Heinzle , Claes Uggla

Recently, the theory of symmetric teleparallel equivalent of general relativity (STEGR) has gained much interest in the cosmology and astrophysics community. Within this theory, we discuss the method of deriving a stellar isotropic model.…

General Relativity and Quantum Cosmology · Physics 2025-04-08 G. G. L. Nashed , Amare Abebe

We construct stable axially symmetric models of elliptical galaxies. The particle density on phase space for these models depends monotonically on the particle energy and on the third component of the angular momentum. They are obtained as…

Astrophysics · Physics 2009-11-07 Yan Guo , Gerhard Rein