Spin polarised nuclear matter and its application to neutron stars

Abstract

An equation of state(EOS) of nuclear matter with explicit inclusion of a spin-isospin dependent force is constructed from a finite range, momentum and density dependent effective interaction. This EOS is found to be in good agreement with those obtained from more sophisticated models for unpolarised nuclear matter. Introducing spin degrees of freedom, it is found that at density about 2.5 times the density of normal nuclear matter the neutron matter undergoes a ferromagnetic transition. The maximum mass and the radius of the neutron star agree favourably with the observations. Since finding quark matter rather than spin polarised nuclear matter at the core of neutron stars is more probable, the proposed EOS is also applied to the study of hybrid stars. It is found using the bag model picture that one can in principle describe both the mass and size as well as the surface magnetic field of hybrid stars satisfactorily.