From the crust to the core of neutron stars on a microscopic basis
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ELEMENTARY PARTICLES AND FIELDS Theory
From The Crust to the Core of Neutron Stars on a Microscopic Basis∗ ˜ 2) M. Baldo1)** , G. F. Burgio1), M. Centelles2) , B. K. Sharma2), and X. Vinas Received June 29, 2013
Abstract—Within a microscopic approach the structure of Neutron Stars is usually studied by modelling the homogeneous nuclear matter of the core by a suitable Equation of State, based on a many-body theory, and the crust by a functional based on a more phenomenological approach. We present the first calculation of Neutron Star overall structure by adopting for the core an Equation of State derived from the Brueckner– Hartree–Fock theory and for the crust, including the pasta phase, an Energy Density Functional based on the same Equation of State, and which is able to describe accurately the binding energy of nuclei throughout the mass table. Comparison with other approaches is discussed. The relevance of the crust Equation of State for the Neutron Star radius is particularly emphasised. DOI: 10.1134/S1063778814080031
1. INTRODUCTION A convergent effort of experimental and theoretical nuclear physics has been developing along several years to determine the structure and properties of Neutron Stars (NS). These studies are expected to reveal the properties and composition of neutron-rich nuclear matter at high density and at the same time the properties of exotic nuclei that are present in the crust and cannot be produced in laboratory because of the large asymmetry. The interpretation of the signals coming from the astrophysical observations on the processes and phenomena that occur in NS requires reliable theoretical inputs. The interplay between the observations and the theoretical predictions has stimulated an impressive progress in the field, and it is expected to help answering many fundamental questions on the properties of matter under extreme conditions and the corresponding elementary processes that can occur. Among others, we mention the maximum mass beyond which a NS collapses to a black hole, the baryon composition of matter at high density, and the properties of extremely asymmetric matter. It is therefore of great interest to have a sound theoretical background for the development of the field, in order to reduce the uncertainty on the possible conclusions one can draw from these ∗
The text was submitted by the authors in English. INFN Sezione di Catania, and Dipartimento di Fisica e Astronomia, Universita` di Catania, Italy. 2) ` Departament d’Estructura i Constituentes de la Materia and ` Institut de Ciencies del Cosmos, Facultat de F ´ısica, Universitat de Barcelona, Spain. ** E-mail: [email protected] 1)
studies. In particular, it can be of great help to develop a unified theory which is able to describe on a microscopic level the overall structure of NS, from the crust to the inner core. This is not a simple task, since the methods developed for homogeneous nuclear matter cannot be easily extended to nuclei and to the non-homogeneous matter present in NS crust. Recently [1–3], an Energy Densit
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