Hyperonic equation of state

An equation of state for cold matter at neutron star densities, >10¹⁴ gm/cm³, is evaluated. The gas is considered to be a degenerate mixture of neutrons, protons, leptons, hyperons and massive baryons. We derive the equilibrium equations including the effects of nuclear interactions among all the hadrons.     

Solar oscillations and the equation of state

Summary Accurate measurements of observed frequencies of solar oscillations are providing a wealth of data on the properties of the solar interior. The frequencies depend on solar structure, and on the properties of the plasma in the Sun. Here we consider in particular the dependence on the thermodynamic state. From an analysis of the equations of stellar structure, and the relevant aspects of the properties of the oscillations, we argue that in the convection zone one can isolate information about the equation of state which is relatively unaffected by other uncertainties in the physics of the solar interior. We review the different treatments that have been used to describe the thermodynamics of stellar plasmas. Through application of several of these to the computation of models of the solar envelope we demonstrate that the sensitivity of the observed frequencies is in fact sufficient to distinguish even quite subtle features of the physics of solar matter. This opens up the possibility of using the Sun as a laboratory for statistical mechanics, under conditions that are out of reach in a terrestrial laboratory.     

Neutron stars and the equation of state

The interior of neutron stars consists of the densest, although relatively cold, matter known in the universe. Here, baryon number densities might reach values close to ten times the nuclear saturation density. These suggest that the constituents of neutron star cores not only consist of nucleons, but also of more exotic baryons like hyperons or a phase of deconfined quarks. We discuss the consequences of such exotic particles on the gross properties and phenomenology of neutron stars. In addition, we determine the general phase structure of dense and also hot matter in the chiral parity-doublet model and confront model results with the recent constraints derived from the neutron star merger observation.     

On the equation of state for the Λ field

The recently detected accelerated expansion of the Universe is related to the existence of a new type of matter called the Λ field or quintessence. Constraints were obtained on its equation of state from the absence of clustering of this matter on scales much smaller than the cosmological horizon. The question of how these constraints affect the possibility of fitting the accelerated expansion by such cosmological models as the Chaplygin gas model is discussed.     

Neutron stars and the dense matter equation of state

Neutron stars provide a unique laboratory with which to study cold, dense matter. The observational quantities of primary astrophysics interest are the maximum mass and the typical radius of a neutron star. These quantities are related to the relative stiffness of neutron-rich matter at supernuclear densities and the density dependence of the nuclear symmetry energy near the nuclear saturation density. The measurements of these nuclear properties via nuclear systematics and structure, heavy-ion collisions and parity-violating electron scattering from neutron-rich nuclei, are discussed. Several new observations, including mass measurements of binary pulsars and a confirmed distance determination for a nearby cooling neutron star, will be summarized. Additionally addressed will be observations of thermal emissions from cooling neutron stars in globular clusters and thermonuclear explosions from accreting stars. It will be demonstrated how this astrophysical data is shedding light on the pressure-density relation of extremely dense matter.     

Parastatistics and the equation of state for the early Universe

The equation of state for an ideal mixture of relativistic quantum gases obeying any (para-)statistics is given. Recursion formulae are obtained for the distribution function and correlations are analysed. The equation of state can be applied to the early Universe, allowing the quarks to be treated either as coloured fermions or (unequivalently) as parafermions of order 3. In the latter case, they exhibit a tendency of aggregate into triads by a mere statistical effect.     

The state equation of superdense degenerate plasma

On the basis of general requirements, the parameters of the hadronic plasma and the state equation of degenerate superdense matter in the whole range of pressures are improved and corrected.     

The equation of state for neutron stars

We present the results of an improved analysis of the equation of state of matter from metallic to nuclear density which takes into account: (a) in the region of low densities (?<10⁴ g cm^?3), the electron correlation energy in the lattice; (b) in the region of medium density (10⁴11 g cm^?3) a more refined discussion of the electron energy; (c) in the region of large densities (4.3×10¹¹ g cm^?3相似文献   

An equation of state at subnuclear densities

An equation of state for cold matter above white dwarf densities is evaluated. The gas is considered to be a mixture of degenerate neutrons, protons and electrons combined with nuclei of one type (that is only oneA andZ value). We derive the equilibrium equations for the mixture and calculate the number densities as well as theA andZ of the nucleus. Finally we calculate an equation of state, which smoothly goes over to that of a neutron, proton electron gas mixture at a density of 5×10¹³ g/cm³.     

Stellar models with generalized polytropic equation of state

We find new classes of exact solutions to the Einstein field equations where the matter distribution satisfies a generalized polytropic equation of state. The matter distribution is uncharged with anisotropic pressures. Equations of state for polytropes and quark matter are contained as special cases. The matter variables and metric potentials can be obtained explicitly. Known solutions, for the choice of the gravitational potential made in this analysis, arise as special cases for particular choice of the equation of state parameters. A detailed physical analysis indicates that the model is well behaved.     

A hydrocode equation of state for SiO2

Abstract— The thermodynamic properties of SiO₂ are approximated over a range of pressures and temperatures important under the extreme conditions achieved in impacts at typical solar system velocities from 5 to about 70 km/s. The liquid/vapor phase curve and critical point of SiO₂ are computed using the equation of state (EOS) program ANEOS. To achieve this goal, two shortcomings of ANEOS are corrected. ANEOS, originally developed at Sandia National Laboratories to describe metals, treats the vapor phase as a monatomic mixture of atoms, rather than molecular clusters. It also assumes a Morse potential for the expanded solid state. Neither of these assumptions is accurate for geologic materials, such as SiO₂, that contain molecular clusters in the vapor phase and are better described by a Mie‐type potential in the solid state. Using the updates described here, an EOS adequate for numerical hydrocode computations is constructed that agrees well with shock data at pressures up to at least 600 GPa and temperatures up to 50,000 K. This EOS also gives a good representation of the liquid/vapor transition at much lower pressures and temperatures. The estimated critical point parameters for SiO₂ are P_c = 0.19 GPa, T_c = 5400K, ρ_c = 550 kg/m³.     

The effects of parametrization of the dark energy equation of state

We investigate in detail the influence of parametrizations of the dark energy equation of state on reconstructing dark energy geometrical parameters,such as the deceleration parameter q(z) and Om diagnostic.We use a type Ia supernova sample,baryon acoustic oscillation data,cosmic microwave background information along with twelve observational Hubble data points to constrain cosmological parameters.With the joint analysis of these current datasets,we find that the parametrizations of w(z) have little influe...     

A note on the equation of state of a scalar field

The energy momentum tensor of a scalar field is considered as being that of a perfect fluid with equation of statep=p(). In the extreme case that the field energy is purely kinetic,p=p, whereas if it is purely potential,p=–.     

A computation of the equation of state for a Fermi gas

Calculation of equation of state in stellar interiors becomes difficult as contained gas deviates from perfect gas. We present a method for the calculation of electron pressure in terms of density and temperature in the presence of degeneracy. The method is applicable forT<10⁹ K, and requires complete ionization.     

On the possible equation of state of a giant molecular cloud

We intend to probe into the nature of the thermodynamical equilibrium of an idealized isothermal, spherical, self-gravitating, giant molecular cloud. The necessity of invoking a frozen in magnetic field has been pointed out for clouds with uniform mass distribution. An equation of state corresponding to the macroscopic statistical equilibrium of the cloud, steeped into a weak homogeneous magnetic field, has also been derived.