Nuclear equation of state

M. Baldo (Ed.), Nuclear Methods and the Nuclear Equation of State (World Scientific, Singapore, 1999). 

NUCLEAR EQUATION OF STATE AND THE STRUCTURE OF NEUTRON STARS... 

Nuclear equation of state and the structure of neutron stars... 

Abstract We discuss the high-density nuclear equation of state within the Brueckner-Hartree-Fock approach. Particular attention is paid to the effects of nucleonic three-body forces, the presence of hyperons, and the joining with an eventual quark matter phase. The resulting properties of neutron stars, in particular the mass-radius relation, are determined. It turns out that stars heavier than 1.3 solar masses contain necessarily quark matter. 

Simulations of this scenario have been performed by Lee (Lee 2001 and references therein) using Newtonian gravity and polytropic equations of state of varying stiffness. Ruffert, Janka and Eberl performed similar simulations but with a detailed microphysics input (nuclear equation of state and neutrino leakage ). In our own simulations of NS-BH mergers we used a relativistic mean field equation of state together with three-dimensional smoothed particle hydrodynamics and a detailed, multiflavour neutrino treatment. 

Gutbrod. II. and II. Stocker The Nuclear Equation of State, Sci Amer.. 58 (November 1991). 

Of course such observables only yield a rather indirect information on the nuclear equation of state. Early investigations of the supernova required a soft equation of state characterized by a compressibility as low as K 140 MeV. A stiffer EOS would not allow sufficient energy to be stored during the collapse such that the subsequent explosion would not reach the surface. Taking into account additional features like effects of neutron heating, a different composition or a rotation of the progenitor star may allow for a supernova even with a stiffer EOS. On the other hand it turned out that also the comparison of experimental data of relativistic heavy ion collisions with corresponding results of computer simulations does not provide a unique answer for the properties of the EOS. Early calculations seemed to show a preference for a stiff EOS with a compressibility as... 

At first sight nuclear structure calculations for infinite nuclear matter and finite nuclei seem to exhibit very similar features (Coester band, effects of relativistic corrections, etc.). A more detailed analysis, however, shows that employing realistic NN interactions substantial differences are obtained in the equation of state for nuclear matter and a finite nucleus. This implies that predictions bn the nuclear equation of state obtained from heavy ion experiments cannot directly be compared to those to be used in studies of astrophysical objects. 

Overall these results for the population of A s under compression indicate potentially major consequences for the nuclear equation of state and we will report on more extensive studies of this phenomenon elsewhere [12]. 

Both BUU- and QMD-like models can be used to investigate the nuclear equation of state (EOS) and the phase diagram for nuclear matter shown schematically in O Fig. 3.3. One parameter of particular concern is the nuclear incompressibility constant K (a subject dealt... 

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