No abstract

A new scheme for testing nuclear matter equations of state (EoSs) at high densities using constraints from neutron star (NS) phenomenology and a flow data analysis of heavy-ion collisions is suggested. An acceptable EoS shall not allow the direct Urca process to occur in NSs with masses below 1.5M , and also shall not contradict flow and kaon production data of heavy-ion collisions. Compact star constraints include the mass measurements of 2.1 ± 0.2M (1σ level) for PSR J0751+1807 and of 2.0 ± 0.1M from the innermost stable circular orbit for 4U 1636-536, the baryon mass-gravitational mass relationships from Pulsar B in J0737-3039 and the mass-radius relationships from quasiperiodic brightness oscillations in 4U 0614+09 and from the thermal emission of RX J1856-3754. This scheme is applied to a set of relativistic EoSs which are constrained otherwise from nuclear matter saturation properties. We demonstrate on the given examples that the test scheme due to the quality of the newly emerging astrophysical data leads to useful selection criteria for the high-density behavior of nuclear EoSs.

Non uniform structures of the nucleon matter at subnuclear densities are numerically studied by means of the density functional theory with relativistic mean-fields coupled with the electric field. A particular role of the charge screening effects is demonstrated.

Abstract. We study the cooling of isolated neutron stars. The main cooling regulators are introduced: equation of state (EoS), thermal transport, heat capacity, neutrino and photon emissivity, superfluid nucleon gaps. The neutrino emissivity includes the main processes. A strong impact of medium effects on the cooling rates is demonstrated. Taking into account medium effects on reaction rates and on nucleon superfluid gaps modern experimental data can be well explained.

Within the real-time formulation of non-equilibrium field theory generalized transport equations are derived avoiding the standard quasiparticle approximation. They permit to include unstable particles into the transport scheme. In order to achieve a self-consistent, conserving and thermodynamically consistent description, we generalize the Baym's Φ-functional method to genuine non-equilibrium processes. This scheme may be closed at any desired loop order of the diagrams of the functional Φ this way defining a consistent effective theory. By means of a first-order gradient approximation the corresponding Kadanoff-Baym equations are converted into a set of coupled equations. This set consists of a time-irreversible generalized kinetic equation for the slowly varying space-time part of the phase-space distributions and a retarded equation, which provides the fast micro-scale dynamics represented by the four-momentum part of the distributions. Thereby, no constraint to the mass shell of the particles is required any further and the corresponding spectral mass distributions are treated dynamically. The description naturally includes all those quantum features already inherent in the corresponding equilibrium limit (Matsubara formalism). Memory effects appearing in collision term diagrams of higher order are discussed. The variational properties of Φ-functional permit to derive a generalized expression for the non-equilibrium kinetic entropy flow, which includes corrections from fluctuations and mass width effects. In special cases an H-theorem can be demonstrated implying that the entropy can only increase with time. Memory effects in the kinetic terms provide corrections to the kinetic entropy flow that in equilibrium limit recover the famous bosonic type T 3 ln T correction to the specific heat of Fermi liquids like Helium-3.

The possibility of structured mixed phases at first order phase transitions in neutron stars is re-examined by taking into account charge screening and surface effects. The transition from the hadron npe phase to the quark phase is studied. Two possibilities, the mixed phase and two separate phases given by the double-tangent (Maxwell) construction are considered. Inhomogeneous profiles of the electric potential and their contribution to the energy are analytically calculated. The electric field configurations determine the droplet size and the geometry of structures.

Within the non-equilibrium Green's function technique on the real time contour, the Φ-functional method of Baym is reviewed and generalized to arbitrary nonequilibrium many-particle systems. The scheme may be closed at any desired order in the number of loops or vertices of the generating functional. It defines effective theories, which provide a closed set of coupled classical field and Dyson equations, which are self-consistent, conserving and thermodynamically consistent. The approach permits to include unstable particles and therefore unifies the description of resonances with all other particles, which obtain a mass width by collisions, decays or creation processes in dense matter. The inclusion of classical fields enables the treatment of soft modes and phase instabilities. The method can be taken as a starting point for adequate and consistent quantum improvements of the in-medium rates in transport theories.GSI-Preprint-98-34, subm. to Nucl. Phys. B

The effect of color superconductivity on the cooling of quark stars and neutron stars with large quark cores is investigated. Various known and new quark-neutrino processes are studied. As a result, stars being in the color flavor locked (CFL) color superconducting phase cool down extremely fast. Quark stars with no crust cool down too rapidly in disagreement with X-ray data. The cooling of stars being in the N_f =2 color superconducting (2SC) phase with a crust is compatible with existing X-ray data. Also the cooling history of stars with hypothetic pion condensate nuclei and a crust does not contradict the data.Comment: 10 pages, 5 figures, accepted for publication in Ap