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Effects of gravitational softening on the global structure of self-gravitating disks in centrifugal equillibrium are examined in relation to hydrodynamical/gravitational simulations. The one-parameter spline softening proposed by Hernquist…

Astrophysics · Physics 2020-11-25 Jesper Sommer-Larsen , Henrik Vedel , Uffe Hellsten

Spatially homogeneous thermal equilibria of self-gravitating gas, being impossible otherwise, are nevertheless allowed in an expanding background accounting for Universe's expansion. Furthermore, a fixed density at the boundary of a…

Astrophysics of Galaxies · Physics 2024-12-13 Zacharias Roupas

We investigate the stability of bounded self-gravitating systems in the canonical ensemble by using a thermodynamical approach. Our study extends the earlier work of Padmanabhan [Astrophys. J. Supp. 71, 651 (1989)] in the microcanonical…

Astrophysics · Physics 2009-11-06 P. -H. Chavanis

The isothermal gas sphere is well known as a powerful tool to model many problems in astrophysics, physics, chemistry, and engineering. This singular differential equation has not an exact solution and solved only by numerical and…

Computational Physics · Physics 2020-10-21 Eltayeb A. Yousif , Ahmed M. A. Adam , Abaker A. Hassaballa1 , Mohamed I. Nouh

We analyze the isothermal property in static fluid spheres within the framework of the modified $f(R, T)$ theory of gravitation. The equation of pressure isotropy of the standard Einstein theory is preserved however, the energy density and…

General Relativity and Quantum Cosmology · Physics 2018-09-26 Sudan Hansraj

We discuss the statistical mechanics of rotating self-gravitating systems by allowing properly for the conservation of angular momentum. We study analytically the case of slowly rotating isothermal spheres by expanding the solutions of the…

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

We construct a toy model for isothermal spheres in Horava gravity, which includes Einstein's gravity if a parameter is appropriately chosen. The equations for the isothermal spheres are derived from the partition function of the gravitating…

General Relativity and Quantum Cosmology · Physics 2021-03-31 Nahomi Kan , Kiyoshi Shiraishi

In the present paper we analyze and discuss some mathematical aspects of the fluid-static configurations of a self-gravitating perfect gas enclosed in a spherical solid shell. The mathematical model we consider is based on the well-known…

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

In the process of protostar formation, astrophysical gas clouds undergo thermodynamically irreversible processes and emit heat and radiation to their surroundings. Due the emission of this energy one can envision an idealized situation in…

General Relativity and Quantum Cosmology · Physics 2016-11-22 Mayer Humi , John Roumas

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

The dynamical equations describing the evolution of a self-gravitating fluid can be rewritten in the form of a Schrodinger equation coupled to a Poisson equation determining the gravitational potential. This wave-mechanical representation…

Astrophysics · Physics 2009-11-07 Peter Coles , Kate Spencer

We open the paper with introductory considerations describing the motivations of our long-term research plan targeting gravitomagnetism, illustrating the fluid-dynamics numerical test case selected for that purpose, that is, a perfect-gas…

The evolution of closed gravitational systems is studied by means of $N$-body simulations. This, as well as being interesting in its own right, provides insight into the dynamical and statistical mechanical properties of gravitational…

Astrophysics · Physics 2009-10-30 Amr El-Zant

The axisymmetric form of the hydrodynamic equations within the smoothed particle hydrodynamics (SPH) formalism is presented and checked using idealized scenarios taken from astrophysics (free fall collapse, implosion and further pulsation…

Astrophysics · Physics 2009-11-13 D. Garcia-Senz , A. Relano , R. M. Cabezon , E. Bravo

We propose a systematic expansion method which is applied to freely evolving granular fluids contained in sufficiently small systems. Restricting ourselves to small systems, we show that there exists a small parameter which characterizes a…

Statistical Mechanics · Physics 2007-05-23 J. Wakou

The classical (i.e. non-quantum) equilibrium statistical mechanics of a two-dimensional one-component plasma (a system of charged point-particles embedded in a neutralizing background) living on a pseudosphere (an infinite surface of…

Statistical Mechanics · Physics 2007-05-23 R. Fantoni , B. Jancovici , G. Téllez

We develop a formulation of global thermodynamics for equilibrium systems under the influence of gravity. The free energy for simple fluids is extended to include a dependence on $(T, V, N, mgL)$, where $L$ represents the vertical system…

Statistical Mechanics · Physics 2025-06-26 Naoko Nakagawa , Shin-ichi Sasa , Takamichi Hirao , Tsuyoshi Shiina , Kyosuke Tachi , Akira Yoshida

Numerical solutions of the isothermal Lane-Emden equation are presented, corresponding to self-gravitating gaseous cores embedded within a finite density envelope of overall cylindrical symmetry. These structures may be members of a…

Astrophysics · Physics 2009-10-31 Charles L. Curry

We present a derivation of the mechanics of isothermal gas spheres directly from the Vlasov--Poisson equation. By extremising the Boltzmann entropy, we obtain the Maxwell--Boltzmann distribution for a self-gravitating isothermal Newtonian…

Astrophysics of Galaxies · Physics 2025-11-13 Steven D Miller
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