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We propose a new approach to calculate the relativistic scalar and vector potentials using a non-relativistic nuclear potential. We first transform the Dirac equation for a nucleon so that the upper component of the Dirac equation becomes a “Schrodinger-like” equation by eliminating the lower component. In the transformation, we can associate the central and the spin-orbit parts of the non-relativistic potentials with the relativistic scalar and vector potentials. We show that the scalar and vector potentials can be written in terms of non-relativistic central and spin-orbit potentials. Using the scalar and vector potentials obtained in this way, we can calculate the mean field wave functions and the single-particle energies. The wave functions, the single-particle energies, and the scalar and vector potentials obtained in this way are found to be similar to those from the usual relativistic Hartree, but withe some differences.

We investigate the structure of neutron stars with strong magnetic fields by using a density-dependent relativistic mean field model. The coupling constant between nucleons and the rho meson in the model is obtained by using the polytropic formula for the symmetry energy in the neutron star. With the density-dependent coupling constant, the effects of the symmetry energy on strongly-magnetized neutron stars are considered in detail for particle fractions and the equation of state. The consequent changes in the masses and the radii of the neutron star are discussed by using the roles of the symmetry energy in the neutron star.

We investigate charge-exchange reactions (CEXRs) and charge-conserving reactions (CCORs) on Mg, Ar, Zr, and Sn isotopes by comparing our theoretical results to relevant experimental data on stable nuclei. As for CEXRs, first, we discuss nuclear beta decay because it may give more convincing input data on the network calculations for successive capture reactions by protons and neutrons. Second, we address the importance of the Gamow Teller (GT) states that are low-lying excited states well known in the conventional nuclear physics while high-lying excited states still remain to be studied. The third topic, which is viable through the CCORs, is the symmetry energy associated with the equation of state of nuclear matter. By using the CCORs, we can study the isoscalar giant dipole resonance (ISGDR) and the pigmy dipole resonance (PDR). We discuss theoretical results regarding these CEXRs and CCORs on 26Mg, 40Ar, 90,92Zr, and 112∼124Sn and compare them with available experimental data. Our calculations are carried out by using the proton-neutron quasi-particle random phase approximation (pnQRPA), the QRPA, the deformed QRPA (DQRPA), the shell model and a hybrid model. Our results are shown to agree with the data available. These nuclear reactions considered in this report will complement capture reactions by protons and neutrons which are of vital importance for understanding the element abundances in the cosmos.

We report the constraints from primordial nucleosynthesis on a possible time-dependent quark mass. The variation may affect binding energies and Q values as well as resonance properties of light elements through the hadron mass variation in the nucleon–nucleon interaction. Updated light-element abundances and uncertainties along with a new detailed analysis of the resonance properties on the crucial 3He(d, p)4He reaction imply a narrower range on the possible quark-mass variations in the early universe. The optimum concordance region reduces to a value consistent with no variation.

We investigate the structure of a proton in free space by using the quark-meson coupling model. In the model, a proton in free space is regarded as a MIT bag with σ, ω and ρ meson fields and the Coulomb potential. With the boundary condition at bag surface, the wave functions of u and d quarks and potentials are calculated self-consistently.

We investigate the properties of an antikaon in medium, regarding itas a MIT bag. We first construct the MIT bag model for a kaon with$\sigma^*$ and $\phi$ in order to describe the interaction of$s$-quarks in hyperonic matter in the framework of the modifiedquark-meson coupling model. The coupling constant $g'^{B_K}_\sigma$in the density-dependent bag constant $B(\sigma)$ is treated as afree parameter to reproduce the optical potential of a kaon in asymmetric matter and all other couplings are determined by usingSU(6) symmetry and the quark counting rule. With various values ofthe kaon potential, we calculate the effective mass of a kaon inmedium to compare it with that of a point-like kaon. We thencalculate the population of octet baryons, leptons and $K^-$ and theequation of state for neutron star matter. The results show thatkaon condensation in hyperonic matter is sensitive to the $s$-quarkinteraction and also to the way of treating the kaon. The mass andthe radius of a neutron star are obtained by solving theTolmann-Oppenheimer-Volkoff equation., Comment: 14 figures

We investigate the properties of the neutron star with relativistic mean field models. We incorporate in the quantum hadrodynamics and in the quark-meson coupling models a possible reduction of meson masses in nuclear matter. The equation of state for neutron star matter is obtained and is employed in Oppenheimer-Volkov equation to extract the maximum mass of the stable neutron star. We find that the equation of state, the composition and the properties of the neutron stars are sensitive to the values of the meson masses in medium., Comment: 18 pages, 5 figures and 2 tables. To be published in EPJA

A four-channel impedance measurement system, including a two-channel goniometer, to analyse human arm movement, was constructed. Impedances and joint angles were simultaneously measured for wrist and elbow movements. As the impedance changes resulting from wrist and elbow movements depended heavily on electrode placement, the optimum electrode configurations for those movements were determined by searching for high correlation coefficients, large impedance changes and minimum interferences in ten subjects (age: 29 +/- 6 years). The optimum electrode configurations showed very strong relationships between the wrist joint angle and forearm impedance (correlation coefficient= 0.95 +/- 0.04) and between the elbow joint angle and upper arm impedance (correlation coefficient= -0.97 +/- 0.03). Although the measured impedance changes of the wrist (1.1 +/-1.5 ohms) and elbow (-5.0 +/-2.9 ohms) varied between individuals, the reproducibilities of wrist and elbow impedance changes of five subjects were 5.8 +/- 1.8% and 4.6 +/- 1.4% for the optimum electrode pairs, respectively. It is proposed that this optimum electrode configuration would be useful for future studies involving the accurate measurement of arm movements by the impedance method.

We calculate the spin deceleration of proto-neutron stars by asymmetric neutrino absorption in the context of a fully relativistic mean field theory. We calculate for the first time the spin deceleration of neutron stars due to asymmetric neutrino absorption in a toroidal magnetic field configurations. We find a surprising effect that the deceleration can much larger for asymmetric neutrino absorption in a toroidal magnetic field than the usually presumed braking due to magnetic dipole radiation. This may explain the observation that magnetars appear to have had a more rapid deceleration in the past., Comment: 13 pages, 1 figure, 1 table

In this work, masses and radii of neutron stars are considered to investigate the effect of nuclear symmetry energy on astrophysical observables. A relativistic mean-field model with density-dependent meson-baryon coupling constants is employed in describing the equation of state of dense nuclear matter, and the density dependencies of the symmetry energies are quoted from the recent phenomenological formulas obtained from heavy-ion data at subnuclear saturation densities. Since hyperons can take part in the $\ensuremath{\beta}$-equilibrium of the dense matter inside neutron stars, we include hyperons in our estimation and their roles are discussed in combination with that of the nuclear symmetry energy.

We have considered the antikaon condensation in a neutron star in the presence of strong magnetic fields by using the modified quark-meson coupling (MQMC) model. The structure of the neutron star is investigated with various magnetic fields and different kaon optical potentials, and the effects of the magnetic fields for kaon condensation is discussed. When employing strong magnetic fields inside a neutron star with hyperons and kaon condensation, the magnetic fields can cause the equation of state to be stiff; thus, a large maximum mass of the neutron star can be obtained., Comment: published in J. Korean Phys.Soc

We calculate the neutrino scattering and absorption on the hot and dense neutron‐star matter with hyperons under the strong magnetic field using perturbative approach. We find that the absorption cross‐sections show the remarkable angular dependence: its strength is reduced in the direction parallel to the magnetic field and enhanced in the opposite direction. This variation becomes about 2.2 % when the magnetic field is about 2×1017 G.

We use the modified quark-meson coupling and the quantum hadrodynamics models to study the properties of neutron star. Coupling constants of both models are adjusted to reproduce the same saturation properties. The onset of kaon condensation in neutron star matter is studied in detail over a wide range of kaon optical potential values. Once the kaon condensation takes place, the population of kaons increases very rapidly, and kaons become the dominant component, possibly making the neutron star matter a kaonic matter if the kaon optical potential is large.

We use the modified quark-meson coupling (MQMC) model to study the composition profile of neutron star matter and compare the results with those calculated by quantum hadrodynamics (QHD). Both MQMC and QHD model parameters are adjusted to produce exactly the same saturation properties so that we can investigate the model dependences of the matter composition at high densities. We consider the possibility of deep kaon optical potential and find that the composition of matter is very sensitive to the interaction strength of kaons with matter. The onset densities of the kaon condensation are studied in detail by varying the kaon optical potentials. We find that the MQMC model produces the kaon condensation at lower densities than QHD. The presence of kaon condensation changes drastically the population of octet baryons and leptons. Once the kaon condensation takes place, the population of kaons builds up very quickly, and kaons become the dominant component of the matter. We find that the {omega} meson plays an important role in increasing the kaon population and suppressing the hyperon population.

The in-medium mass of a $\thetaplus$, $\mtheta^*$, in cold symmetric nuclear matter is calculated by using the quark-meson coupling model. The $\Theta^+$ is treated as an MIT bag with the quark content $uudd\bar s$. Bag parameters for a free $\thetaplus$ are fixed to reproduce the observed mass of the $\thetaplus$. In doing so, we use three different values of the $s$-quark mass since the mass of the $s$-quark is not well known. As usual, the strengths of the $u$ and $d$ quark couplings to $\sigma$- and $\omega$-meson fields are determined to fit the nuclear saturation properties. However, the coupling constant $g_\sigma^s$ between the $s$-quark and the $\sigma$-meson cannot be fixed from the saturation properties, and thus we treat $g_\sigma^s$ as a free parameter and investigate how $\mtheta^*$ depends on $g_\sigma^s$. %$\mtheta^*$ is calculated up to 2.5 times the nuclear saturation density, %and we find that We find that $\mtheta^*$ depends significantly on the value of $g_\sigma^s$ but not on the mass of the $s$-quark. Chemical potentials of the $\Theta^+$ and the $K+N$ system are calculated to discuss the decay of a $\Theta^+$ in nuclear matter. We calculate the effective mass of a kaon in nuclear matter in two ways; using the optical potential of $K^-$ in matter and using quark model. By comparing the effective masses calculated from these two methods, we find the magnitude of the real part of the optical potential that is consistent with the usual quark model is about 100 MeV.

We summarize several new developments in the nuclear equation of state for supernova simulations and neutron stars. We discuss an updated and improved Notre-Dame-Livermore Equation of State (NDL EoS) for use in supernovae simulations. This Eos contains many updates. Among them are the effects of 3- body nuclear forces at high densities and the possible transition to a QCD chiral and/or super-conducting color phase at densities. We also consider the neutron star equation of state and neutrino transport in the presence of strong magnetic fields. We study a new quantum hadrodynamic (QHD) equation of state for neutron stars (with and without hyperons) in the presence of strong magnetic fields. The parameters are constrained by deduced masses and radii. The calculated adiabatic index for these magnetized neutron stars exhibit rapid changes with density. This may provide a mechanism for star-quakes and flares in magnetars. We also investigate the strong magnetic field effects on the moments of inertia and spin down of neutron stars. The change of the moment of inertia associated with emitted magnetic flares is shown to match well with observed glitches in some magnetars. We also discuss a perturbative calculation of neutrino scattering and absorption in hot and dense hyperonic neutron-star matter in the presence of a strong magnetic field. The absorption cross-sections show a remarkable angular dependence in that the neutrino absorption strength is reduced in a direction parallel to the magnetic field and enhanced in the opposite direction. The pulsar kick velocities associated with this asymmetry comparable to observed pulsar velocities and may affect the early spin down rate of proto-neutron star magnetars with a toroidal field configuration., Comment: 6 pages, revised 1 figure, International Symposium "Exotic Nuclear Structure From Nucleons" (ENSFN 2012)

We investigate the effect of density dependent magnetic moment of baryons in strong magnetic fields for neutron star with hyperons and kaons. Under strong magnetic fields, all charged particles experience Landau quantization, so that chemical potentials, equation of state and mass-radius relations depend on magnetic fields strength. In particular, since magnetic fields are combined with magnetic moments of baryons, we calculate the neutron star with hyperons and kaon condensation, and investigate the effect of density dependent magnetic moment of baryon octet obtained by the quark-meson coupling model. The effect is maximally 0.1M for hyperonic matter, but in kaonic matter, its effect can be ignored.