Wednesday, July 24, 2013

1307.6190 (Tobias Fischer et al.)

Symmetry energy impact in simulations of core-collapse supernovae    [PDF]

Tobias Fischer, Matthias Hempel, Irina Sagert, Yudai Suwa, Jürgen Schaffner-Bielich
We present a review of a broad selection of nuclear matter equations of state (EOSs) applicable in core-collapse supernova studies. The large variety of nuclear matter properties, such as the symmetry energy, which are covered by these EOSs leads to distinct outcomes in supernova simulations. Many of the currently used EOS models can be ruled out by nuclear experiments, many-body calculations of nuclear matter, and astrophysical observations of neutron stars. In particular, the two classical supernova EOS describe neutron matter poorly. Nevertheless, we explore their impact in supernova simulations since they have been commonly used in astrophysics. They serves as extremely soft and stiff representative nuclear models. Hence, the corresponding supernova simulations represent two extreme cases, e.g. with respect to the protoneutron star compactness and shock evolution. Moreover, in multi-dimensional supernova simulations EOS differences have a strong effect on the explosion dynamics. Because of the extreme behaviors of the classical supernova EOSs we also include DD2, a relativistic mean field EOS with density-dependent couplings. This model is in satisfactory agreement with many current constraints from nuclear theory and astrophysical observations. It is the first time that DD2 has been applied to core-collapse supernova simulations and compared with the classical supernova EOS. We find that the overall behavior of the latter EOS in supernova simulations lies in between the two extreme classical EOSs. As pointed out in previous studies, we confirm the effect of the symmetry energy on the electron fraction of the protoneutron star and its evolution. Furthermore, we study the possible impact of quark matter at high densities and light nuclear clusters at low and intermediate densities. None of these additional degrees of freedom are covered by saturation properties of nuclear matter...
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