Properties of collective flow and pion production in intermediate-energy heavy-ion collisions with a relativistic quantum molecular dynamics model

The relativistic mean-field approach was implemented in the Lanzhou quantum molecular dynamics transport model(LQMD.RMF). Using the LQMD.RMF, the properties of collective flow and pion production were investigated systematically for nuclear reactions with various isospin asymmetries. The directed and elliptic flows of the LQMD.RMF are able to describe the experimental data of STAR Collaboration. The directed flow difference between free neutrons and protons was associated with the stiffness of the symmetry energy, that is, a softer symmetry energy led to a larger flow difference. For various collision energies, the ratio between the π^(-) and π^(+) yields increased with a decrease in the slope parameter of the symmetry energy. When the collision energy was 270 MeV/nucleon, the single ratio of the pion transverse momentum spectra also increased with decreasing slope parameter of the symmetry energy in both nearly symmetric and neutron-rich systems.However, it is difficult to constrain the stiffness of the symmetry energy with the double ratio because of the lack of threshold energy correction on the pion production.

Strangeness to increase the density of finite nuclear systems in constraining the high-density nuclear equation of state

As the high-density nuclear equation of state(EOS) is not very well constrained, we suggest that the structural properties from the finite systems can be used to extract a more accurate constraint. By including the strangeness degrees of freedom, the hyperon or anti-kaon, the finite systems can then have a rather high-density core which is relevant to the nuclear EOS at high densities directly. It is found that the density dependence of the symmetry energy is sensitive to the properties of multi-K hypernuclei, while the high-density EOS of symmetric matter correlates sensitively to the properties of kaonic nuclei.

Neutron star core-crust transition and the crustal moment of inertia in the nonlinear relativistic Hartree approximation

We investigate the effects of theσmeson mass(m_(σ)),symmetry energy,and slope of the symmetry energy on the neutron star core-crust transition density and the crustal moment of inertia(ΔI/I)in the nonlinear relativistic Hartree approach(RHA),which includes vacuum polarization.Although the core-crust transition density(ρ_(t)),pressure(P_(t)),and neutron star radius(R),which are all dependent on the symmetry energy,contribute to determiningΔI/I,we find that changing only the slope of symmetry energy within a reasonable range is not sufficient to reachΔI/I≥7%to achieve the large glitches of the Vela pulsar.However,since all three factors(ρ_(t),P_(t),and R)increase with the increase in mσthrough scalar vacuum polarization,adjusting mσcan easily achieveΔI/I≥7%.

Elastic scattering based on energy-dependent relativistic Love-Franey model at energies between 20 and 800 MeV

In order to investigate the elastic scattering,we fit scattering observables of the weighted fits(WF16)with the relativistic Love-Franey(RLF)model.The masses,cutoff parameters,and initial coupling strengths of RLF are assumed to be independent of energy.Because the energy boundary between low energy and high energy is around 200 Me V,the masses,cutoff parameters,and initial coupling strengths of RLF are obtained by fitting scattering observables of WF16 at an incident energy of 200 MeV.With the masses,cutoff parameters,and initial coupling strengths as the input,the energy-dependent RLF model is constructed over the laboratory energy range of 20 to 800MeV within a unified fit.To examine the validity of this fit,we investigate p+^(208)Pbelastic scattering for various energies.Although the scattering observables of pp and pn of 200 MeV best fit the values of WF16,the RLF model of 200 MeV without the Pauli blocking(PB)corrections fails to describe the experimental differential cross sections,analyzing powers,and spinrotation functions.When the PB corrections are taken into account for various energies,the RLF model can well describe the experimental data of p+^(208)Pbelastic scattering.

Dark matter with chiral symmetry admixed with hadronic matterin compact stars

Using the two-fluid Tolman-Oppenheimer-Volkoff equation,the properties of dark matter(DM)admixed neutron stars(DANSs)have been investigated.In contrast to previous studies,we find that an increase in the maximum mass and a decrease in the radius of 1.4 M_(⊙)NSs can occur simultaneously in DANSs.This stems from the ability of the equation of state(EOS)for DM to be very soft at low density but very stiff at high density.It is well known that the IU-FSU and XS models are unable to produce a neutron star(NS)with a maximum mass greater than 2.0 M_(⊙).However,by considering the IU-FSU and XS models for DANSs,there are interactions with DM that can produce a maximum mass greater than 2.0 M_(⊙)and a radius of 1.4 M_(⊙)NSs below 13.7 km.When considering a DANS,the difference between DM with chiral symmetry(DMC)and DM with meson exchange(DMM)becomes obvious when the central energy density of DM is greater than that of nuclear matter(NM).In this case,the DMC model with a DM mass of 1000 MeV can still produce a maximum mass greater than 2.0 M_(⊙)and a radius of a 1.4 M_(⊙)NS below 13.7 km.Additionally,although the maximum mass of the DANS using the DMM model is greater than 2.0 M_(⊙),the radius of a 1.4 M_(⊙)NS can surpass 13.7 km.In the two-fluid system,the maximum mass of a DANS can be larger than 3.0 M_(⊙).Consequently,the dimensionless tidal deformabilityΛCP of a DANS with 1.4 M_(⊙),which increases with increasing maximum mass,may be larger than 800 when the radius of the 1.4 M_(⊙)DANS is approximately 13.0 km.