Thermodynamics of a system of leptons,photons and interacting nucleons

The thermodynamics of matter composed of interacting nucleons with an admixutre of leptons and photons is investigated in the density-temperature region relevant to the problem of supernova explosion. A quantum mechanical calculation is carried out using Skyrme effective interaction between nucleons. The equation of state is shown to soften below the nuclear density and suddenly stiffen in the transnuclear density region, a condition which is suitable for producing a strong bounce shock that is needed for effective supernova explosion and leaving a remnant neutron star behind.     

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   

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.     

Neutron star models based on an improved equation of state

Using an equation of state for cold degenerate matter which takes nuclear forces and nuclear clustering into account, neutron star models are constructed. Stable models were obtained in the mass range above 0.065M and density range 10^14.08 to 10^15.4 gm/cm³. All of these models were found to be bound. The outer crystalline layer of the star was found to have a thickness of 200 m or more depending on the mass of the model.     

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.     

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.     

A microscopic equation of state for protoneutron stars

We study the structure of protoneutron stars within the finite-temperature Brueckner–Bethe–Goldstone many-body theory. If nucleons, hyperons, and leptons are present in the stellar core, we find that neutrino trapping stiffens considerably the equation of state, because hyperon onsets are shifted to larger baryon density. However, the value of the critical mass turns out to be smaller than the “canonical” value 1.44M _⊙. We find that the inclusion of a hadron-quark phase transition increases the critical mass and stabilizes it at about 1.5–1.6M _⊙.      

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.     

Higher dimensional cosmological model with a time-dependent equation of state

A homogeneous cosmological model in higher dimension is obtained assuming a timedependent equation of state. It is observed that as usual 3-D space expands, extra space (space belonging to the other dimensions) reduces with time, thus exhibiting the desired feature of dimensional reduction. The dynamical behavior of the model is examined and it is noted that with a decrease in extra space the observable 3-D space entropy increase, thus accounting for the large value of entropy observable at present.     

Emulating the OPAL equation of state

The equation of state for the structure of the Sun and stars has to be precise to allow comparisons with observations, i.e., helioseismic inversions of thermodynamic quantities. Among the two of the most popular formalisms are (1) the OPAL equation of state developed at Livermore and (2) the Mihalas-Hummer-Däppen (MHD) equation of state. While OPAL has a solid theoretical foundation, and matches the observational data better, the MHD formalism is more intuitive, easy to realize, and has the possibility of adjustable parameters. Furthermore, it an open-source product in contrast to the proprietary OPAL. Recently a version of MHD has been obtained by including the so-called “Plank-Larkin partition function” and by adding scattering-state terms. The resulting formalism matches OPAL rather well. Here, we report on the next logical step, the implementation of this MHD upgrade into the simple and popular CEFF equation of state. Such an implementation will make it a flexible and convenient tool, allowing an approximative on-line implementation of OPAL in solar and stellar models.     

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.     

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=–.     

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.     

Non-stationary motion of a rotating infinitely flattened self-gravitating system near an equilibrium state

An example of a rotating infinitely flattened self-gravitating particle system in steady state is considered. Non-stationary motion of the system in the neighborhood of this equilibrium solution is determined through the sencond-order perturbation. The first order perturbation terms give rise to a configuration of straight bars emanating from the center which become skewed under the influence of the second-order terms. In the case of a single bar, as in a barred spiral, the skewing is in the arms leading or arms trailing sense, according to whether the system is developing away from or approaching the equilibrium state.     

Hydromagnetic gravitational instability of an infinite cylinder of a compressible fluid

The gravitational instability of an infinite cylinder of a self-gravitating, perfectly-conducting, compressible fluid subjected to a uniform axial magnetic field is investigated. A generalised dispersion relation describing the stability characteristics of the configuration is given. The gravitational instability of the cylinder is found to be worsened in the presence of the compressibility effects in the fluid.     

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.