Symmetry energy for asymmetric nuclear matter at subsaturation densities was investigated in the framework of an isospin-dependent quantum molecular dynamics model. A single ratio of neutrons and protons is compared with the experimental data of Famiano et al. [Phys. Rev. Lett. 97, 052701 (2006)] We have also performed a comparison for the double ratio with experimental as well as different theoretical results of Boltzmann-Uehling-Uhlenbeck in 1997, Isospin-dependent Boltzmann-Uehling-Uhlenbeck in 2004, Boltzmann-Nordeim-Vlasov, and Improved Quantum Molecular Dynamics models. It is found that the double ratio predicts the softness of symmetry energy, which is a little underestimated in the single ratio. Furthermore, the study of the single ratio is extended for different kinds of fragments, while the double ratio is extended for different neutron-rich isotopes of Sn.

Thermodynamic and transport properties of nuclear fireball created in the central region of heavyion collisions below 400 MeV/nucleon are investigated within the isospin-dependent quantum molecular dynamic (IQMD) model. These properties including the density, temperature, chemical potential, entropy density (s) and shear viscosity (η), are calculated by a generalized hot Thomas Fermi formulism and a parameterized function, which was developed by Danielewicz. As the collision goes on, a transient minimal η/s = 5/4π − 10/4π occurs in the largest compression stage. Besides, the relationship of η/s to temperature (T ) in the freeze-out stage displays a local minimum which is about 9-20 times 1/4π around T = 8-12 MeV, which can be argued as indicative of a liquid gas phase transition. In addition, the influences of nucleon-nucleon (NN) cross section (σNN ) and symmetry energy coefficient (Cs) are also discussed, and it is found that the results are sensitive to σNN but not to Cs. PACS numbers: 25.70.-z, 21.65.Mn

The α cluster states are discussed in a model frame of extended quantum molecular dynamics. Different alpha cluster structures are studied in details, such as 8 Be two-α cluster structure, 12 C triangle structure, 12 C chain structure, 16 O chain structure, 16 O kite structure, and 16 O square structure. The properties studied, include as the width of wave packets for different α clusters, momentum distribution, and the binding energy among α clusters. It is also discussed how the α cluster degree of freedom affects nuclear collective vibrations. The cluster configurations in 12 C and 16 O are found to have corresponding characteristic spectra of giant dipole resonance (GDR), and the coherences of different α clusters's dipole oscillation are described in details. The geometrical and dynamical symmetries of α-clustering configurations are responsible for the number and centroid energies of peaks of GDR spectra. Therefore, the GDR can be regarded as an effective probe to diagnose different α cluster configurations in light nuclei.