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A global equilibrium state of a spin polarized fluid that undergoes constant acceleration along the stream lines is described as a solution of recently introduced perfect-fluid hydrodynamic equations with spin 1/2.

Nuclear Theory · Physics 2018-08-15 Wojciech Florkowski , Enrico Speranza , Francesco Becattini

Using the conservation laws for charge, energy, momentum, and angular momentum, we derive hydrodynamic equations for the charge density, local temperature, and fluid velocity, as well as for the spin tensor, starting from local equilibrium…

Nuclear Theory · Physics 2018-04-18 Wojciech Florkowski , Bengt Friman , Amaresh Jaiswal , Enrico Speranza

The first static spherically symmetric perfect fluid solution with constant density was found by Schwarzschild in 1918. Generically, perfect fluid spheres are interesting because they are first approximations to any attempt at building a…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Petarpa Boonserm , Matt Visser , Silke Weinfurtner

We first establish existence for all positive time near equilibrium for the moving interface problem between the Navier-Stokes equations for the evolving fluid phase (moved by the fluid velocity) and an elastic body modelled by the linear…

Analysis of PDEs · Mathematics 2026-03-06 Daniel Coutand

Within $R^2$ gravity, we study the linear stability of strongly gravitating spherically symmetric configurations supported by a polytropic fluid. All calculations are carried out in the Jordan frame. It is demonstrated that, as in general…

General Relativity and Quantum Cosmology · Physics 2020-09-29 Vladimir Dzhunushaliev , Vladimir Folomeev

In the present paper we study a conformally flat generalized Ricci recurrent perfect fluid spacetime with constant Ricci scalar as a solution of modified $F(R)$-gravity theory. We show that a Robertson-Walker spacetime is generalized Ricci…

General Relativity and Quantum Cosmology · Physics 2021-05-17 Avik De , Tee-How Loo , Raja Solanki , P. K. Sahoo

For spherically symmetric relativistic perfect fluid models, the well-known Buchdahl inequality provides the bound $2 M/R \leq 8/9$, where $R$ denotes the surface radius and $M$ the total mass of a solution. By assuming that the ratio…

General Relativity and Quantum Cosmology · Physics 2007-08-27 J. Mark Heinzle

We argue that an arbitrary general relativistic static anisotropic fluid sphere, (static and spherically symmetric but with transverse pressure not equal to radial pressure), can nevertheless be successfully mimicked by suitable linear…

General Relativity and Quantum Cosmology · Physics 2017-11-29 Petarpa Boonserm , Tritos Ngampitipan , Matt Visser

We consider a concircularly semi-symmetric metric connection and its application. The Ricci tensors with respect to the concircularly semi-symmetric metric connection are symmetric, and they are used to define Einstein type manifolds. In…

Differential Geometry · Mathematics 2026-05-19 Miroslav Maksimović , Milan Zlatanović , Marija Najdanović

The law of balance of angular momentum is shown to imply the existence of absolute time, a fundamental physical quantity that is independent of the motion or position of the observer. Absolute time implies the notion of absolute…

General Physics · Physics 2023-03-29 A. Paglietti

Rayleigh-Benard convection in a cylindrical container can take on many different spatial forms. Motivated by the results of Hof, Lucas and Mullin [Phys. Fluids 11, 2815 (1999)], who observed coexistence of several stable states at a single…

Fluid Dynamics · Physics 2010-04-02 Katarayna Borońska , Laurette S. Tuckerman

Static spherically symmetric solutions to the Einstein-Euler equations with prescribed central densities are known to exist, be unique and smooth for reasonable equations of state. Some criteria are also available to decide whether…

General Relativity and Quantum Cosmology · Physics 2019-03-01 Lars Andersson , Annegret Y. Burtscher

We express Einstein's field equations for a spherically symmetric ball of general fluid such that they are conducive to an initial value problem. We show how the equations reduce to the Vaidya spacetime in a non-null coordinate frame,…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Paul Lasky , Anthony Lun

We study the motion of an incompressible perfect liquid body in vacuum. This can be thought of as a model for the motion of the ocean or a star. The free surface moves with the velocity of the liquid and the pressure vanishes on the free…

Analysis of PDEs · Mathematics 2007-05-23 Hans Lindblad

We classify all spherically symmetric and homothetic spacetimes that are allowed kinematically by constructing them from a small number of building blocks. We then restrict attention to a particular dynamics, namely perfect fluid matter…

General Relativity and Quantum Cosmology · Physics 2008-11-26 B. J. Carr , Carsten Gundlach

We briefly review the basic features of a new framework for relativistic perfect fluid hydrodynamics of polarized systems consisting of particles with spin one half. Using this approach we numerically study the stability of a stationary…

In this paper we study the system of two falling balls in continuous time. We modell the system by a suspension flow over a two dimensional, hyperbolic base map. By detailed analysis of the geometry of the system we identify special…

Dynamical Systems · Mathematics 2016-08-03 Péter Bálint , András Némedy Varga

A perfectly elastic beam is situated on top of a two dimensional fluid canister. The beam is deforming in accordance to an interaction with a Navier-Stokes fluid. Hence a hyperbolic equation is coupled to the Navier-Stokes equation. The…

Analysis of PDEs · Mathematics 2024-02-19 Sebastian Schwarzacher , Pei Su

The paper is devoted to the study of the motion of one-dimensional rigid bodies during a free fall in a quasi-Newtonian hyperviscous fluid at low Reynolds number. We show the existence of a steady solution and furnish sufficient conditions…

Mathematical Physics · Physics 2016-03-23 Giulio G. Giusteri , Alfredo Marzocchi , Alessandro Musesti

In this work, we obtained exact solutions of Einstein's field equations for plane symmetric cosmological models by assuming that thy admit conformal motion. The space-time geometry of these solutions is found to be nonsingular, non-vacuum…

General Relativity and Quantum Cosmology · Physics 2025-01-07 Ragab M. Gad , Awatif Al-Jedani , Shahad T. Alsulami