Thermodynamical Properties of Asymmetric Nuclear Matter in Generalized Hybrid Derivative Coupling Model

Abstract

In this work we have studied the properties of asymmetric nuclear matter at zero and finite temperature in a wide range of density and asymmetry parameter using recently proposed generalized hybrid derivative coupling model. The temperature and asymmetry dependence of the bulk quantities such as compressibility, binding energy per nucleon, saturation density, chemical potential, entropy per nucleon, etc. have been explored. This is useful to understand the dynamics of supernova explosion. We have studied the density and temperature dependence of symmetry energy and briefly discussed its role in the evaluation of proton fraction at T = 0, in equilibrium with neutron rich matter. We have also studied proton fraction for T =1= 0 by free energy minimization. Dependence of bulk properties on the hybridization parameter of our model has been studied. The asymmetry and temperature dependence of the characteristics of liquid-gas phase transition have also been studied. We have compared our results with those of other investigators. §1. IntroductionThe study of the properties of cold and hot asymmetric nuclear matter is very important to understand the dynamics of iron-core collapse of some massive stars which produce type II supernova, the mechanism of supernova explosion, the structure of neutron-star remnants and also unstable neutron rich nuclei produced in the laboratory.!) For this purpose we need an equation of state (EOS) which is reliable at high density and/or non-zero temperature. The later stage of the collapsing presupernova core involves neutron rich matter with N ~ 2Z (or proton concentration (Z/(N + Z) of about 1/3) at moderate temperature T = 1 -10 MeV and densities up to about 4P02) where Po is the saturation density of nuclear matter. Neutron star structure involves almost pure neutron matter with N » Z, essentially at zero temperature and densities up to about (8 -1O)Po. 2 )The problem of asymmetric nuclear matter for zero and non-zero temperature has been investigated by several investigators who used non-relativistic BruecknerBethe-Goldstone approach. 2 ),3) They assumed potential theory description. In this problem several workers 4 ) have performed relativistic Dirac-Brueckner calculations, based on a one-meson exchange interaction only. Prakash and Ainsworth 5 ) applied field theoretic method based on chiral sigma model to study asymmetric nuclear matter properties at zero temperature. We intend to study the properties of asymmetric nuclear matter using a recently proposed general form of hybrid derivative coupling model 6 ) considering different values of asymmetric parameter (3( = (N -Z) / (N + Z)) and hybridization parameter Q. It may be noted that several investigators 7 ) have at

Generalized Hybrid Derivative Coupling Model With Dilaton Field to Study Phase Transition From Nuclear Matter to Quark Matter

“…[1][2][3] We give here a brief description of the above model for isospin symmetric nuclear matter where additional contribution due to dilaton or glueball field is considered. The general form of Lagrangian density, describing nucleons, omega mesons and sigma mesons, for isospin symmetric nuclear matter is given by…”

“…1 Earlier we have applied this generalized hybrid derivative coupling model to study the properties of symmetric and asymmetric nuclear matter at zero and finite temperatures and also the phase transition from nuclear matter and neutron matter to quark matter. 2,3 In this work we have just introduced an additional scalar isoscalar field, i.e. dilaton or glueball field (χ) in the Lagrangian.…”