TY - JOUR

T1 - A new equation of state for core-collapse supernovae based on realistic nuclear forces and including a full nuclear ensemble

AU - Furusawa, S.

AU - Togashi, H.

AU - Nagakura, H.

AU - Sumiyoshi, K.

AU - Yamada, S.

AU - Suzuki, H.

AU - Takano, M.

N1 - Funding Information:
SF and HN were supported by Japan Society for the Promotion of Science Postdoctoral Fellowships for Research Abroad. Some numerical calculations were carried out on the PC cluster at the Center for Computational Astrophysics, National Astronomical Observatory of Japan. This work was supported by the RIKEN iTHES Project and in part by the usage of supercomputer systems through the Large Scale Simulation Program (Nos. 15/16/-08,16/17-11) of High Energy Accelerator Research Organization (KEK) and Post-K Projects (hp 150225, hp160071, hp160211,hp170031,hp170230) at K-computer, RIKEN AICS as well as the computational resources provided by RCNP at Osaka University, YITP at Kyoto University, University of Tokyo and JLDG. This work was supported by a Grant-in-Aid for the Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan (24103006, 24244036, 16H03986, 15K05093, 24105008, 25400275, 26104006).
Publisher Copyright:
© 2017 IOP Publishing Ltd.

PY - 2017/7/25

Y1 - 2017/7/25

N2 - We have constructed a nuclear equation of state (EOS) that includes a full nuclear ensemble for use in core-collapse supernova simulations. It is based on the EOS for uniform nuclear matter that two of the authors derived recently, applying a variational method to realistic two- and three-body nuclear forces. We have extended the liquid drop model of heavy nuclei, utilizing the mass formula that accounts for the dependences of bulk, surface, Coulomb and shell energies on density and/or temperature. As for light nuclei, we employ a quantum-theoretical mass evaluation, which incorporates the Pauli- and self-energy shifts. In addition to realistic nuclear forces, the inclusion of in-medium effects on the full ensemble of nuclei makes the new EOS one of the most realistic EOSs, which covers a wide range of density, temperature and proton fraction that supernova simulations normally encounter. We make comparisons with the FYSS EOS, which is based on the same formulation for the nuclear ensemble but adopts the relativistic mean field theory with the TM1 parameter set for uniform nuclear matter. The new EOS is softer than the FYSS EOS around and above nuclear saturation densities. We find that neutron-rich nuclei with small mass numbers are more abundant in the new EOS than in the FYSS EOS because of the larger saturation densities and smaller symmetry energy of nuclei in the former. We apply the two EOSs to 1D supernova simulations and find that the new EOS gives lower electron fractions and higher temperatures in the collapse phase owing to the smaller symmetry energy. As a result, the inner core has smaller masses for the new EOS. It is more compact, on the other hand, due to the softness of the new EOS and bounces at higher densities. It turns out that the shock wave generated by core bounce is a bit stronger initially in the simulation with the new EOS. The ensuing outward propagations of the shock wave in the outer core are very similar in the two simulations, which may be an artifact, though, caused by the use of the same tabulated electron capture rates for heavy nuclei ignoring differences in the nuclear composition between the two EOSs in these computations.

AB - We have constructed a nuclear equation of state (EOS) that includes a full nuclear ensemble for use in core-collapse supernova simulations. It is based on the EOS for uniform nuclear matter that two of the authors derived recently, applying a variational method to realistic two- and three-body nuclear forces. We have extended the liquid drop model of heavy nuclei, utilizing the mass formula that accounts for the dependences of bulk, surface, Coulomb and shell energies on density and/or temperature. As for light nuclei, we employ a quantum-theoretical mass evaluation, which incorporates the Pauli- and self-energy shifts. In addition to realistic nuclear forces, the inclusion of in-medium effects on the full ensemble of nuclei makes the new EOS one of the most realistic EOSs, which covers a wide range of density, temperature and proton fraction that supernova simulations normally encounter. We make comparisons with the FYSS EOS, which is based on the same formulation for the nuclear ensemble but adopts the relativistic mean field theory with the TM1 parameter set for uniform nuclear matter. The new EOS is softer than the FYSS EOS around and above nuclear saturation densities. We find that neutron-rich nuclei with small mass numbers are more abundant in the new EOS than in the FYSS EOS because of the larger saturation densities and smaller symmetry energy of nuclei in the former. We apply the two EOSs to 1D supernova simulations and find that the new EOS gives lower electron fractions and higher temperatures in the collapse phase owing to the smaller symmetry energy. As a result, the inner core has smaller masses for the new EOS. It is more compact, on the other hand, due to the softness of the new EOS and bounces at higher densities. It turns out that the shock wave generated by core bounce is a bit stronger initially in the simulation with the new EOS. The ensuing outward propagations of the shock wave in the outer core are very similar in the two simulations, which may be an artifact, though, caused by the use of the same tabulated electron capture rates for heavy nuclei ignoring differences in the nuclear composition between the two EOSs in these computations.

KW - equation of state

KW - nuclear abundances

KW - nuclear forces

KW - supernovae

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UR - http://www.scopus.com/inward/citedby.url?scp=85028041489&partnerID=8YFLogxK

U2 - 10.1088/1361-6471/aa7f35

DO - 10.1088/1361-6471/aa7f35

M3 - Article

AN - SCOPUS:85028041489

VL - 44

JO - Journal of Physics G: Nuclear and Particle Physics

JF - Journal of Physics G: Nuclear and Particle Physics

SN - 0954-3899

IS - 9

M1 - 094001

ER -