Within the framework of Lanzhou quantum molecular dynamics transport model, the correlation of initial deformation and isospin diffusion is systematically investigated in collisions of $^{ 238}$U + $^{ 238}$U. The impacts of the collision centrality, symmetry energy and initial configuration on the collective flows, neutron/proton and $\pi^{ -}/\pi^{ +}$ ratios have been systematically investigated. It is found that the broader neutron-rich region is formed in the body-body collisions in comparison with the ones in the tip-tip collisions. The neutron-star matter might be created in the density region of 0.2-0.5 $\rho_{ 0}$ (the normal nuclear density $\rho_{ 0}$=0.165 fm$^{ -3}$) formed in the $^{ 238}$U + $^{ 238}$U reaction at the incident energy of 500 MeV/nucleon. The elliptic flows of protons are related to the incident energy, collision centrality, symmetry energy and collision orientation. The hard symmetry energy enables the larger free neutron/proton ratio at the beam energy of 500 MeV/nucleon. However, the neutron/proton and $\pi^{ -}/\pi^{ +}$ ratios in the density regime of $1.2\leq \rho/\rho_{ 0}\leq1.8$ are enhanced by the soft symmetry energy with the slope parameter of L=42 MeV.
Categories: nucl-th