The mean field properties and equation of state for asymmetric nuclear matter are studied by using a simple effective interaction which has a single finite range Gaussian term. The study of finite nuclei with this effective interaction is done by means of constructing a quasilocal energy density functional for which the single particle equations take the form of Skryme-Hartree-Fock equations. The predictions of binding energies and charge radii of spherical nuclei are found to be compatible with the results of standard models as well as experimental data.
The properties of spin polarized pure neutron matter and symmetric nuclear matter are studied using the finite range simple effective interaction, upon its parametrization revisited. Out of the total twelve parameters involved, we now determine ten of them from nuclear matter, against the nine parameters in our earlier calculation, as required in order to have predictions in both spin polarized nuclear matter and finite nuclei in unique manner being free from uncertainty found using the earlier parametrization. The information on the effective mass splitting in polarized neutron matter of the microscopic calculations is used to constrain the one more parameter, that was earlier determined from finite nucleus, and in doing so the quality of the description of finite nuclei is not compromised. The interaction with the new set of parameters is used to study the possibilities of ferromagnetic and antiferromagnetic transitions in completely polarized symmetric nuclear matter. Emphasis is given to analyze the results analytically, as far as possible, to elucidate the role of the interaction parameters involved in the predictions.
The importance of the fourth and higher order terms in the Taylor series expansion of the energy of the isospin asymmetric nuclear matter in the study of the neutron star crust-core phase transition is investigated using the finite range simple effective interaction. Analytic expressions for the evaluation of the second and fourth order derivative terms in the Taylor series expansion for any general finite range interaction of Yukawa, exponential or Gaussian form have been obtained. The effect of the nuclear matter incompressibility, symmetry energy and slope parameters on the predictions for the crust-core transition density is examined. The crustal moment of inertia is calculated and the prediction for the radius of the Vela pulsar is analyzed using different equations of state.
The momentum and density dependence of the mean field in nuclear matter has been studied with phenomenological effective interactions with particular emphasis on the influence of the functional form of the interaction in determining the high density and high momentum behaviour of the mean field. Emphasis is also given to choosing the effective interaction in a form simple enough to permit analytical calculations of various properties of nuclear matter with a minimum number of adjustable parameters. These simple effective interactions are found to have a zero-range density-dependent part similar to Skyrme interactions and a long-range densityindependent part of conventional form, such as Yukawa, Gaussian and exponential. It is observed that the high density and the high momentum behaviour of the mean field in nuclear matter is essentially governed by the nature of the density dependence and the precise functional form of the long-range part of the exchange component of the effective interaction. The parameters of these interactions can be constrained to obtain a mean field in nuclear matter which is independent of the functional form of the exchange interaction in the range of momentum k = 0-5 fm −1 and up to a density four times the standard nuclear matter density. However, beyond this range the functional form of the exchange interaction becomes important in determining the momentum and density dependence of the mean field in nuclear matter.
The thermal evolution of properties of neutron rich asymmetric nuclear matter such as entropy density, internal energy density, free energy density and pressure are studied in the non-relativistic mean field theory using finite range effective interactions. In this framework the thermal evolution of nuclear matter properties is directly connected to the neutron and proton effective mass properties. Depending on the magnitude of neutron-proton effective mass splittings, two distinct behaviours in the thermal evolution of nuclear matter properties are noticed.
Spatially homogeneous and anisotropic LRS Bianchi type-I string cosmological models are studied in the frame work of general relativity when the source for the energy momentum tensor is a bulk viscous fluid containing one dimensional strings. A barotropic equation of state for the pressure and density is assumed to get determinate solutions of the field equations. The bulk viscous pressure is assumed to be proportional to the energy density. The physical and kinematical properties of the models are discussed. The role of bulk viscosity in getting an inflationary phase in the universe is studied.Keywords Anisotropic universe · Viscosity · Cosmic strings · Viscous pressure PACS 11.27.+d · 98.80.Cq · 95.30.Sf String Cosmological models have generated a lot of research interest in recent times because of their roles in describing different interesting phenomena. In gauge theories with spontaneously broken symmetries strings arise as a random network of stable line like topological defects during the phase transition in the early universe. Massive closed loops of string serve as seeds for the formation of large structures like galaxies and cluster of galaxies. While matter is
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