A chiral symmetric relativistic mean field model with logarithmic sigma potential

We develop a chiral symmetric relativistic mean field model with logarithmic sigma potential derived in the strong coupling limit of the lattice QCD. We find that both of the nuclear matter and finite nuclei are well described in the present model. The normal vacuum is found to have global stability at zero and finite baryon densities, and an equation of state with moderate stiffness (K ~ 280 MeV) is obtained. The binding energies and charge radii of Z closed even-even nuclei are well reproduced in a wide mass range from C to Pb isotopes, except for the underestimates of binding energies in several jj closed nuclei.Comment: 19 pages, 6 figure

Hypernuclei and nuclear matter in a chiral SU(3) RMF model

We develop a chiral SU(3) RMF model for octet baryons, as an extension of the recently developed chiral SU(2) RMF model with logarithmic sigma potential. For Sigma-meson coupling, strong repulsion(SR) and weak repulsion(WR) cases are examined in existing atomic shift data of Sigma^-. In both of these cases, we need an attractive pocket of a few MeV depth around nuclear surface.Comment: 4 pages, 8 figures, to appear in the proceedings of the IX International Conference on Hypernuclear and Strange Particle Physics (HYP2006

Three-dimensional Boltzmann-Hydro code for core-collapse in massive stars I. special relativistic treatments

We propose a novel numerical method for solving multi-dimensional, special relativistic Boltzmann equations for neutrinos coupled to hydrodynamics equations. It is meant to be applied to simulations of core-collapse supernovae. We handle special relativity in a non-conventional way, taking account of all orders of v/c. Consistent treatment of advection and collision terms in the Boltzmann equations is the source of difficulties, which we overcome by employing two different energy grids: Lagrangian remapped and laboratory fixed grids. We conduct a series of basic tests and perform a one-dimensional simulation of core-collapse, bounce and shock-stall for a 15M_{sun} progenitor model with a minimum but essential set of microphysics. We demonstrate in the latter simulation that our new code is capable of handling all phases in core-collapse supernova. For comparison, a non-relativistic simulation is also conducted with the same code, and we show that they produce qualitatively wrong results in neutrino transfer. Finally, we discuss a possible incorporation of general relativistic effects in our method.Comment: 25 pages, 22 figures, submitted to Ap

Stellar Core Collapse with Hadron-Quark Phase Transition

Hadronic matter undergoes a deconfinement transition to quark matter at high temperature and/or high density. It would be realized in collapsing cores of massive stars. In the framework of MIT bag model, the ambiguities of the interaction are encapsulated in the bag constant. Some progenitor stars that invoke the core collapses explode as supernovae, and other ones become black holes. The fates of core collapses are investigated for various cases. Equations of state including the hadron-quark phase transition are constructed for the cases of the bag constant B=90, 150 and 250 MeV fm^{-3}. To describe the mixed phase, the Gibbs condition is used. Adopting the equations of state with different bag constants, the core collapse simulations are performed for the progenitor models with 15 and 40Msolar. If the bag constant is small as B=90 MeV fm^{-3}, an interval between the bounce and black hole formation is shortened drastically for the model with 40Msolar and the second bounce revives the shock wave leading to explosion for the model with 15Msolar.Comment: 5 pages, 5 figures, references corrected, accepted for publication in A&

Effects of Magnetic Fields on Proto-Neutron Star Winds

We discuss effects of magnetic fields on proto-neutron star winds by performing numerical simulation. We assume that the atmosphere of proto-neutron star has a homogenous magnetic field (ranging from ~10^{12} G to ~10^{15} G) perpendicular to the radial direction and examine the dependence of the three key quantities (dynamical time scale, electron fraction, and entropy per baryon) for the successful r-process on the magnetic field strength. Our results show that even with a magneter-class field strength, ~10^{15} G, the feature of the wind dynamics varies only little from that of non-magnetic winds, and that the condition for successful r-process is not realized.Comment: submitted to Progress of Theoretical Physics. 28 pages, 13 figure

Exploring Hadron Physics in Black Hole Formations: a New Promising Target of Neutrino Astronomy

The detection of neutrinos from massive stellar collapses can teach us a lot not only about source objects but also about microphysics working deep inside them. In this study we discuss quantitatively the possibility to extract information on the properties of dense and hot hadronic matter from neutrino signals coming out of black-hole-forming collapses of non-rotational massive stars. Based on our detailed numerical simulations we evaluate the event numbers for SuperKamiokande with neutrino oscillations being fully taken into account. We demonstrate that the event numbers from a Galactic event are large enough not only to detect it but also to distinguish one hadronic equation of state from another by our statistical method assuming the same progenitor model and non-rotation. This means that the massive stellar collapse can be a unique probe into hadron physics and will be a promising target of the nascent neutrino astronomy.Comment: 7 pages, 3 figures, accepted for publication in PR