The Study Of Phase Transition In High Density Nuclear Matter And Properties Of Hybrid Stars

In order to distinguish different compact objects,people easily bethink of the difference of mass-radius relations between them that may be caused by different equations of state(EOS).After the introduction of the investigative background about the hybrid stars as well as the related astrophysics problems, we describe the EOS of normal nuclear and strange quark matter,then by using Baym-Pethick-Sutherland model describing subnuclear densities,relativistic mean field theory describing nuclear densities and also effective mass bag model considering medium effects for quark matter,we discuss the phase transition in neutron stars,and finally obtain the EOS of hybrid stars. We find that the EOS becomes softer for the appearance of mixed phase.This makes the radius of hybrid stars lying between the neutron stars and strange stars with the same masses.The research of Wang et al implies that strange quark matter has larger bulk viscosity compared to normal nuclear matter.lt enlightens people to confirm new compact objects through the studies on differences of rotation periods that caused by dynamics of compact matter. Especially in recent years,people pay more attention to the bulk viscosity of strange quark and neutron matter after the finding of important r-mode instability in rotating compact stars.Here we study the coefficient of viscosity in mixed phases, calculate the contributions of two kinds of non-leptonic reactions(the non-leptonic decay of hyperons and quarks).Our results suggest that coefficients of bulk viscosity become larger to strongly restrain the r-mode instability. Compared to neutron and strange stars,hybrid stars may support faster critical rotation frequencies ,which may explain the observation data better.lt also points that faster rotating pulsars may imply the existence of strange matter in objects,which can't tell whether it would be hyperon or strange quark matter.