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Hydrostatic equilibrium

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


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TL;DR: In this paper, a quantitative in situ formation scenario for the massive core planet HD-149026-b was presented, which is possible if it is formed in situ in a relatively low-pressure nebula.
Abstract: Today, many extrasolar planets have been detected. Some of them exhibit properties quite different from the planets in our Solar system and they have eluded attempts to explain their formation. One such case is HD 149026 b. It was discovered by Sato et al. A transit-determined orbital inclination results in a total mass of . The unusually small radius can be explained by a condensible element core with an inferred mass of for the best-fitting theoretical model. In the core accretion model, giant planets are assumed to form around a growing core of condensible materials. With increasing core mass, the amount of gravitationally bound envelope mass increases. This continues up to the so-called critical core mass – the largest core allowing a hydrostatic envelope. For larger cores, the lack of static solutions forces a dynamic evolution of the protoplanet, accreting large amounts of gas or ejecting the envelope in the process. This would prevent the formation of HD 149026 b. By studying all possible hydrostatic equilibria we could show that HD 149026 b can remain hydrostatic up to the inferred heavy core. This is possible if it is formed in situ in a relatively low-pressure nebula. This formation process is confirmed by fluid-dynamic calculations using the environmental conditions as determined by the hydrostatic models. We present a quantitative in situ formation scenario for the massive core planet HD 149026 b. Furthermore, we predict a wide range of possible core masses for close-in planets like HD 149026 b. This is different from migration, where typical critical core masses should be expected.

20 citations

Journal ArticleDOI
TL;DR: In this article, a linear anelastic-vortex model is derived using assumptions appropriate to waves on vortices with scales similar to tropical cyclones, where the horizontal variations in the thermodynamic variables describing the reference state are appreciably longer than the waves on the vortex.
Abstract: A linear anelastic-vortex model is derived using assumptions appropriate to waves on vortices with scales similar to tropical cyclones. The equation set is derived through application of a multiple-scaling technique, such that the radial variations of the thermodynamic fields are incorporated into the reference state. The primary assumption required for the model is that the horizontal variations in the thermodynamic variables describing the reference state are appreciably longer than the waves on the vortex. This new version of the anelastic system makes no approximation to the requirements for hydrostatic and gradient wind balance, or the buoyancy frequency, in the core of the vortex. A small but measurable improvement in the performance of the new equation set is demonstrated through simulations of gravity waves and vortex–Rossby waves in a baroclinic vortex.

20 citations

Journal ArticleDOI
TL;DR: In this article, first-principles calculations for low temperature superconductors based on plane-wave pseudo-potential density functional theory within the generalized gradient approximation are implemented, and the elastic moduli of Nb�3Sn and Nb¯¯¯¯3Al and those superconductivities in the presence of hydrostatic pressure are evaluated.
Abstract: The low temperature superconducting materials, such as Nb 3Sn and Nb 3Al, have similar crystal structures and elastic properties. However, their critical-temperature degradations always show the distinct way under mechanical stresses. In this study, first-principles calculations for the low temperature superconductors based on plane-wave pseudo-potential density functional theory within the generalized gradient approximation are implemented, and the elastic moduli of Nb 3Sn and Nb 3Al and those superconductivities in the presence of hydrostatic pressure are evaluated. The Debye temperatures are obtained by the bulk moduli and shear moduli of superconducting materials. The MacMillan equation is further used to acquire the critical temperatures of Nb 3Sn and Nb 3Al under different hydrostatic pressures. It is found that the elastic constants and bulk moduli of the low temperature superconductors are enhanced by the applied hydrostatic pressure, while the critical temperatures usually are decreased with the pressure. Additionally, the decrease of critical-temperature for Nb 3Sn is more sensitive to the hydrostatic pressure than the one for Nb 3Al. The prediction results show good agreement with the experimental results in the literatures qualitatively.

20 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method to test the gravitational interactions in the outskirts of galaxy clusters by combining the gas and lensing measurements of the cluster. But their method is limited to the Coma cluster.
Abstract: We propose a novel method to test the gravitational interactions in the outskirts of galaxy clusters. When gravity is modified, this is typically accompanied by the introduction of an additional scalar degree of freedom, which mediates an attractive fifth force. The presence of an extra gravitational coupling, however, is tightly constrained by local measurements. In chameleon modifications of gravity, local tests can be evaded by employing a screening mechanism that suppresses the fifth force in dense environments. While the chameleon field may be screened in the interior of the cluster, its outer region can still be affected by the extra force, introducing a deviation between the hydrostatic and lensing mass of the cluster. Thus, the chameleon modification can be tested by combining the gas and lensing measurements of the cluster. We demonstrate the operability of our method with the Coma cluster, for which both a lensing measurement and gas observations from the X-ray surface brightness, the X-ray temperature, and the Sunyaev-Zel'dovich effect are available. Using the joint observational data set, we perform a Markov chain Monte Carlo analysis of the parameter space describing the different profiles in both the Newtonian and chameleon scenarios. We report competitive constraints on the chameleon field amplitude and its coupling strength to matter. In the case of f(R) gravity, corresponding to a specific choice of the coupling, we find an upper bound on the background field amplitude of |f_{R0}|<6*10^{-5}, which is currently the tightest constraint on cosmological scales.

20 citations

Journal ArticleDOI
TL;DR: In this article, a new class of astrophysical objects where the self-gravity of the dust is balanced by the force arising from shielded electric fields on the charged dust is introduced.
Abstract: We show the existence of a new class of astrophysical objects where the self-gravity of the dust is balanced by the force arising from shielded electric fields on the charged dust. The problem of equilibrium dust clouds is formulated in terms of an equation of hydrostatic force balance together with an equation of state. Because of the dust charge reduction at high dust density, the adiabatic index reduces from two to zero. This gives rise to a mass limit MAS for the maximum dust mass that can be supported against gravitational collapse by these fields. If the total mass MD of the dust in the interstellar cloud exceeds MAS, the dust collapses, while in the case MD < MAS, equilibrium may be achieved. The physics of the mass limit is similar to the Chandrasekhar's mass limit for compact objects, such as white dwarfs and neutron stars.

19 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023282
2022708
202167
202089
201998
201893