Microscopic Study of Nuclear “Pasta” by Quantum Molecular Dynamics

Collapse driven supernovae (SNe) and the following formation of neutron stars (NSs) are the most dramatic processes during the stellar evolution. These objects provide not only astrophysically significant phenomena but also interesting material phases inside them; both are strongly connected with each other. At subnuclear densities in NS crusts and SN cores, nuclei are expected to have exotic structures such as rod-like and slab-like shape etc., which are called nuclear “pasta”. 1) This prediction has been obtained by previous studies 2), 3) based on free energy calculations assuming specific nuclear shapes. These works clarify that the nuclear shape is determined by a subtle balance between nuclear surface and Coulomb energies. However, the formation process of the “pasta” phases has not been discussed except for some limited cases which are based on perturbative approaches. 1), 6) It is important to adopt microscopic and dynamical approach which allows arbitrary nuclear structures in order to understand the formation of the non-spherical nuclei. We have started studying dense matter by the QMD 4) simulation whose final goal is to obtain a realistic picture about NS crusts and SN cores. As the first step of our quest, we will answer the following question in this study: “Can the ’pasta’ phases be formed dynamically?”