Color screening effect and nucleon-nucleon interaction

title: Color screening effect in b anti-b system

title: Color screening effect in the quark potential model
abstract: By using the color confinement potential which includes the color screening effect, we studied the baryon spectra and the nucleon-nucleon interaction. The results show that the color screening effect not only improves the baryon spectrum calculation, but also can solve the long-tail problem of the color Van der Waals force. A part of the medium attraction of the nuclear force can be obtained from the color Van der Waals force.

title: A Unified Description of N-N and Y-N Interactions on Quark Model*
abstract: A quark-quark interaction is derived from the Linear expression of Lagrangian which is invariant under the SU(3)(L) x SU(3)(R) infinitesimal transformation, and further used to make a unified study on the N-N and Y-N scattering processes.

title: The energy of six-quark cluster system
abstract: The energies of the (OS)(6) six-quark cluster states are calculated in the chiral SU(3) quark model. The results show that some states with higher strange number have more attraction from the chiral SU(3) coupling; and this feature is interesting in discussing if there exists some narrow width six-quark states with high strangeness.

title: A study of nucleon-nucleon interaction from the quark-antiquark pair creation model
abstract: The NN interaction is studied with the quark cluster model by including the equivalent one-meson-exchange potentials and two-pion-exchange potential, which are constructed from the quark-antiquark pair-creation transition potential. The results show that the long-range part of the equivalent meson-exchange potential is similar to that of the conventional meson-exchange potential, and the medium-range part of the equivalent meson-exchange potential is attractive, but the strength of the latter is not enough to explain the phase shifts of S-wave NN scattering.

title: Shallow decay phase of GRB X-ray afterglows from relativistic wind bubbles
abstract: The postburst object of a GRB is likely to be a highly magnetized, rapidly rotating compact object (e.g., a millisecond magnetar), which could produce an ultrarelativistic electron-positron-pair wind. The interaction of such a wind with an outwardly expanding fireball ejected during the burst leads to a relativistic wind bubble (RWB). We investigate the properties of RWBs and use this model to explain the shallow decay phase of the early X-ray afterglows observed by Swift.  We numerically calculate the dynamics and radiative properties of RWBs.  We find that RWBs can fall into two types: forward-shock-dominated and reverse-shock-dominated bubbles. Their radiation during a period of ~$10^{2}{-}10^{5}$ s is dominated by the shocked medium and the shocked wind, respectively, based on different magnetic energy fractions of the shocked materials. For both types, the resulting light curves always have a shallow decay phase, as discovered by Swift. In addition, we provide an example fit to the X-ray afterglows of GRB 060813 and GRB 060814 and show that they could be produced by forward-shock-dominated and reverse-shock-dominated bubbles, respectively. This implies that, for some early afterglows (e.g., GRB 060814), the long-lasting reverse shock emission is strong enough to explain their shallow decay phase.

title: Modelling the multiwavelength light curves of PSR B1259−63/SS 2883
abstract: PSR B1259-63/SS 2883 is a binary system in which a 48-ms pulsar orbits around a Be star in a high eccentric orbit with a long orbital period of about 3.4 yr. Extensive broadband observational data are available for this system from radio band to very high energy (VHE) range. The multi-frequency emission is unpulsed and nonthermal, and is generally thought to be related to the relativistic electrons accelerated from the interaction between the pulsar wind and the stellar wind, where X-ray emission is from the synchrotron process and the VHE emission is from the inverse Compton (IC) scattering process. Here a shocked wind model with variation of the magnetization parameter σ is developed for explaining the observations. By choosing proper parameters, our model could reproduce two-peak profile in X-ray and TeV light curves. The effect of the disk exhibits an emission and an absorption components in the X-ray and TeV bands respectively. We suggest that some GeV flares will be produced by Doppler boosting the synchrotron spectrum. This model can possibly be used and be checked in other similar systems such as LS I+61 o 303 and LS 5039.

title: GRB 080319B: optical and gamma-ray emissions from internal forward-reverse shocks

title: Effect of a strong magnetic field on the surface electric field of strange stars
abstract: We made a detailed study of the properties of the electron layer near the quark surface of strange stars with strong (${\sim}10^{14}{-}10^{17}$ G) magnetic fields. The electrostatic potential and the electric field at the quark surface were calculated as functions of the magnetic field intensity of bare strange stars. Using an ultrastrong ($B\geq 2.5\times10^{16}$ G) magnetic field, we found that the distribution of electrons becomes an exponential function of radial distance, which is quite different in a magnetic field-free case. We also calculated the variation in gap width between the strange core and the normal nuclear crust for strange stars, which is due to magnetic field effect.

title: Long-term evolution and gravitational wave radiation of neutron stars with differential rotation induced by r-modes
abstract: In a second-order r-mode theory, Sa and Tome found that the r-mode oscillation in neutron stars (NSs) could induce stellar differential rotation, which naturally leads to a saturated state of the oscillation. Based on a consideration of the coupling of the r-modes and the stellar spin and thermal evolution, we carefully investigate the influences of the differential rotation on the long-term evolution of isolated NSs and NSs in low-mass X-ray binaries, where the viscous damping of the r-modes and its resultant effects are taken into account. The numerical results show that, for both kinds of NSs, the differential rotation can significantly prolong the duration of the r-modes. As a result, the stars can keep nearly a constant temperature and constant angular velocity for over a thousand years. Moreover, the persistent radiation of a quasi-monochromatic gravitational wave would also be predicted due to the long-term steady r-mode oscillation and stellar rotation. This increases the detectability of gravitational waves from both young isolated and old accreting NSs.