Hydrostatic equilibrium

About: Hydrostatic equilibrium is a research topic. Over the lifetime, 2451 publications have been published within this topic receiving 62172 citations.

Moment of inertia of slowly rotating anisotropic neutron stars in f(R,T) gravity

Abstract: Within the framework of [Formula: see text] theories of gravity, we investigate the hydrostatic equilibrium of anisotropic neutron stars with a physically relevant equation of state (EoS) for the radial pressure. In particular, we focus on the [Formula: see text] model, where [Formula: see text] is a minimal coupling constant. In the slowly rotating approximation, we derive the modified TOV equations and the expression for the relativistic moment of inertia. The main properties of neutron stars, such as radius, mass and moment of inertia, are studied in detail. Our results reveal that the main consequence of the [Formula: see text] term is a substantial increase in the surface radius for low enough central densities. Nevertheless, such a term slightly modifies the total gravitational mass and moment of inertia of the slowly rotating stars. Furthermore, the changes are noticeable when anisotropy is incorporated into the stellar fluid, and it is possible to obtain higher masses that are consistent with the current observational data.

Deviations from the Hydrostatic and Thermal Equilibrium in a Quasi-Static Star

Abstract: The force acting upon a moving mass element is resolved mainly into the pressure force and the buoyancy force of Archimedes The resolution is meaningful relative to both the duration of the motion, and the creation of vorticity The dynamic time-scale of a star is introduced as the characteristic time needed for a mass element to travel from the star’s surface over a fraction of the total radius due to a deviation of the dominant pressure force from its equilibrium value The energy exchange between moving mass elements is shown to be generally small in a star, except near the surface Therefore, the isentropic approximation can be adopted for stellar perturbations Finally, a local criterion for stability with respect to convection is derived by consideration of the slow isentropic motion of a bubble under the influence of the buoyancy force of Archimedes

On internal gravity waves generated by local disturbances

Abstract: : The internal waves generated by a time dependent local disturbance in an incompressible continuously stratified fluid are examined. Following the Love theory of wave motion in heterogeneous liquids, the motion is regarded as a small perturbation about the state of hydrostatic equilibrium. For simplicity, the equilibrium density profile is taken to be exponential. It was found that, for a disturbance having a simple harmonic time dependency, the ratio of the disturbance frequency to the Vaisala frequency determines whether progressive internal waves are present or not and in which regions. The propagation of the wave front of the internal waves generated by an instantaneous source was also analyzed.

Pressure transfer functions for interfacial fluid problems

Abstract: We make a consistent derivation, from the governing equations, of the pressure transfer function in the small-amplitude Stokes wave regime and the hydrostatic approximation in the small-amplitude solitary water wave regime, in the presence of a background shear flow. The results agree with the well-known formulae in the zero vorticity case,but they incorporate the effects of vorticity through solutions to the Rayleigh equation. We extend the results to permit continuous density stratification and to internal waves between two constant-density fluids. Several examples are discussed.