Antic, Sofija (2018)
Generalized relativistic mean-field model with non-linear derivative nucleon-meson couplings for nuclear matter and finite nuclei.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

The equation of state (EOS) for highly compressed dense matter is one of the main concerns of nuclear astrophysics in recent years. It is essential for modeling compact astrophysical objects like neutron stars (NS), their mergers and core-collapse supernovae (CCSN). It also sets the conditions for the creation of chemical elements in the universe, in particular for the r-process whose astrophysical site is still under debate. Therefore, it is an active theoretical and experimental research topic. At present, a realistic and quantitative description of dense matter is not available from first principles using the basic theory of quantum chromodynamics (QCD). Hence, a large variety of phenomenological models has been developed for describing nuclear systems. These models depend on a number of adjustable parameters that have to be determined by data. It is essential for the further development of the field to determine the most realistic parameter sets and to use them consistently. New and more precise constraints on EOS parameters are becoming available with the advancement of technology and novel astrophysical observations and laboratory experiments conducted. As a consequence we are able to provide models that can be further used in many studies, both for nuclear structure and astrophysical applications.

In this work an extended relativistic mean-field (RMF) model, the density-dependent (DD) non-linear derivative (NLD), or in short DD-NLD model, is developed. The novelty is combining density-dependent nucleon-meson couplings with the energy dependence introduced in the nucleon self-energies in order to reproduce the experimental behavior of the optical potential. The model is applied to the description of infinite nuclear matter, focusing on the high density region above nuclear saturation, and used to obtain the NS EOS at zero temperature. In order to determine the model parameters they are fitted to nuclear matter properties at saturation density as well as to selected properties of several finite nuclei among which are binding energies, charge and diffraction radii, surface thicknesses, etc. The obtained set of parameters is used in the calculation of the NS mass-radius relation by solving the Tolman-Oppenheimer-Volkoff equations. This was considered only for nuclear systems at vanishing temperature. For general astrophysical applications however, e.g. in order to provide EOS tables for simulations of CCSN, it is necessary to extend the theoretical description to finite temperatures. Since the developed DD-NLD model has a very general form, it can in principle be extended to temperature dependent cases. For the purpose of this work, the extended temperature dependent model for nuclear matter is developed, but in the limit of low temperatures, up to about 20 MeV. This allows to study the liquid-gas phase transition for nuclear matter expected at sub-saturation densities, covering the full range of isospin asymmetries. A study of the spinodal and binodal regions of instability and phase coexistence is performed. We discuss the influence of the energy-dependent self-energies in the EOS model with increasing temperature and the effects it has on the liquid-gas phase transition.

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