Describing Proto-Neutron Stars With The Relativistic Mean Field Theory

The physics of compact objects like neutron stars offers an intriguing interplay between nuclear processes and astrophysical observables. Neutron stars exhibit conditions far from those encountered on Earth. It is the equation of state (EOS) that determines the characteristics of neutron stars such as the possible range of mass, the mass-radius relation, and the cooling rate. The possible way to find the EOS of neutron star matter is to extend the successful theory in nuclear and particle physics. The relativistic mean field (RMF) theory, which provides a good description of the bulk properties of nuclear matter as well as a large number of single-particle properties of finite nuclei, is used in this thesis in order to present the characters of hot neutron stars(also is called proto-neutron star, in short PNS) in various circumstances.Studying the distribution and scale of PNS theoretically can get the evolution character of neutron stars, and which may offer its inner structure information reversely. So I investigated the EOS and characters of neutron star by using the temperature-dependent RMF theory. The influence of effective interactions including DDME1,TW99,NL2,TM1,TM2,GL85 and GL97 on the constitutes, equation of state and masses of neutron star are studied at finite temperature (T=20Mev). And the transformation circs with the temperature is studied at the same time. It's found that the different effective interactions give us different descriptions of neutron star. And the EOS become stiffer while the temperature increases, and the higher the temperature is, the stiffer the EOS is.In the investigation of the structure of neutron star shortly after it is born, which neutrino are trapped in the core of the star. I studied proto-neutron star consists of only neutron and proton and proto-neutron star including hyperons respectively. And the entropy per baryon is changing from 0 to 2 .The results reveal that the influences of entropy towards the characters and EOS is quite smaller than that of hyperon.At the last part, we studied the contributions of theσ^* andφmesons on the properties of neutron star matter at S=1. The comparisons between the two cases had analyzed particularly. It's found that with the contributions of theσ^* andφmesons, the number of hyperons increases, the critical baryon density of hyperon appearance decreases, the transition densityρ_OH ofhyperon stars decreases, the equation of state turns soft, the maximum mass of neutron star decreases and the corresponding radius increases, the central density,the central energy density and the central pressure are all reduced.