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We study spherical and disk clusters in a near-Keplerian potential of galactic centers or massive black holes. In such a potential orbit precession is commonly retrograde, i.e. direction of the orbit precession is opposite to the orbital…

Astrophysics · Physics 2008-11-26 E. V. Polyachenko , V. L. Polyachenko , I. G. Shukhman

Some models (such as the Skyrme model, a low-energy effective field theory for QCD) suggest that the high-density matter prevailing in neutron star interiors may be significantly anisotropic. Anisotropy is known to affect the bulk…

General Relativity and Quantum Cosmology · Physics 2015-06-05 Hector O. Silva , Caio F. B. Macedo , Emanuele Berti , Luís C. B. Crispino

In this paper, we develop a new relativistic compact stellar model for a spherically symmetric anisotropic matter distribution. The model has been obtained through generating a new class of solutions by invoking the Tolman {\em ansatz} for…

General Relativity and Quantum Cosmology · Physics 2020-11-25 Piyali Bhar , Shyam Das , Bikram Keshari Parida

We present here how the gravothermal or Antonov's instability, which was originally formulated in the microcanonical ensemble, is modified in the presence of a cosmological constant and in the canonical ensemble. In contrast to the…

Cosmology and Nongalactic Astrophysics · Physics 2013-03-22 Minos Axenides , George Georgiou , Zacharias Roupas

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

Several phenomena related to the critical behaviour of non-interacting electrons in a disordered 2d tight-binding system with a magnetic field are studied. Localization lengths, critical exponents and density of states are computed using…

Disordered Systems and Neural Networks · Physics 2009-10-31 Marc Ruhlander , C. M. Soukoulis

We model a compact radiant star that undergoes gravitational collapse from a certain initial static configuration until it becomes a black hole. The star consists of a fluid with anisotropy in pressures, bulk viscosity, in addition to the…

General Relativity and Quantum Cosmology · Physics 2023-04-26 A. C. Mesquita , M. F. A. da Silva

This paper presents a hydrodynamic and thermodynamic treatment of a radiant star model that undergoes a dissipative gravitational collapse, from a certain initial configuration until it becomes a black hole. The collapsing star consists of…

General Relativity and Quantum Cosmology · Physics 2022-04-27 J. M. Z. Pretel , M. F. A. da Silva

We discuss the possibility to analyze the problem of gravothermal catastrophe in a new way, by obtaining thermodynamical equations to apply to a selfgravitating system. By using the King distribution function in the framework of statistical…

Astrophysics of Galaxies · Physics 2014-05-20 Marco Merafina , Daniele Vitantoni

We investigate the nature of the critical behaviour of the random-anisotropy Heisenberg model (RAM), which describes a magnetic system with random uniaxial single-site anisotropy, such as some amorphous alloys of rare earths and transition…

Disordered Systems and Neural Networks · Physics 2007-05-23 Francesco Parisen Toldin , Andrea Pelissetto , Ettore Vicari

This paper investigates instability ranges of a cylindrically symmetric collapsing stellar object in Brans-Dicke theory of gravity. For this purpose, we use perturbation approach in the modified field equations as well as dynamical…

General Relativity and Quantum Cosmology · Physics 2016-07-20 M. Sharif , Rubab Manzoor

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

It is well known that the density and anisotropy profile in the inner regions of a stellar system with positive phase-space distribution function are not fully independent. Here we study the interplay between density profile and orbital…

Astrophysics · Physics 2009-11-13 Luca Ciotti , Lucia Morganti

We investigate the thermodynamic properties of stellar self-gravitating system arising from the Tsallis generalized entropy. In particular, physical interpretation of the thermodynamic instability, as has been revealed by previous…

Condensed Matter · Physics 2009-11-07 A. Taruya , M. Sakagami

We investigate the effects of relativity on the gravitational instability of finite isothermal gaseous spheres. In the first part of the paper, we treat the gravitational field within the framework of Newtonian mechanics but we use a…

Astrophysics · Physics 2009-11-07 Pierre-Henri Chavanis

The self-similar equilibrium models of self-gravitating, rotating, isothermal systems are investigated analytically. In these models the rotation velocity is constant and the density varies as $\frac{f(\theta, \phi)}{r^2}$, where $r$ and…

Astrophysics · Physics 2009-11-06 Mohsen Shadmehri , Jamshid Ghanbari

We investigate the nature of the critical behavior of the random-anisotropy Heisenberg model (RAM), which describes a magnetic system with random uniaxial single-site anisotropy, such as some amorphous alloys of rare earths and transition…

Disordered Systems and Neural Networks · Physics 2007-05-23 Francesco Parisen Toldin , Andrea Pelissetto , Ettore Vicari

A two-dimensional fracture model where the interaction among elements is modeled by an anisotropic stress-transfer function is presented. The influence of anisotropy on the macroscopic properties of the samples is clarified, by…

Statistical Mechanics · Physics 2008-02-22 R. C. Hidalgo , S. Zapperi , H. J. Herrmann

We investigate the structure and stability of the thermal equilibrium states of a spherically symmetric self-gravitating system in a $D$-dimensional asymptotically Anti-de Sitter(AdS) spacetime. The system satisfies the Einstein-Vlasov…

General Relativity and Quantum Cosmology · Physics 2022-09-07 Hiroki Asami , Chul-Moon Yoo

This paper investigates dynamics of axial reflection symmetric model in self-interacting Brans-Dicke gravity for anisotropic fluid. We formulate hydrodynamical equations and discuss oscillations using time-dependent perturbation for both…

General Relativity and Quantum Cosmology · Physics 2016-07-22 M. Sharif , Rubab Manzoor