## Chief

Takashi Nakatsukasa, Professor Dr. Takashi Nakatsukasa graduated from Kyoto University in 1994, with a doctor degree in physics. |

## Outline of the field

Atomic nucleus is an extremely high density matter located in the center of atoms. It is a finite quantum many-body system composed of two kinds of fermions, proton and neutron, bound by nuclear force. A complex nature of the nuclear force brings unique and diverse properties of atomic nucleus. One of current concerns in nuclear physics is a problem of origin of elements: where and how nuclei are synthesized in the universe. To answer the question, we need to understand structure and reactions of nuclei far away from stability. Describing and understanding atomic nucleus starting solely from underlying nuclear force is a long-standing goal of theoretical nuclear physics. Since atomic nucleus is a quantum system composed of many-fermions, theoretical nuclear physics is also intimately related to other fields exploring quantum many-body systems like atomic and molecular physics, condensed matter physics, and quantum chemistry.

## Nuclear dynamics in time-dependent density functional theory

The research conducted by the theoretical nuclear physics group puts emphasis on development of computational approaches for quantum dynamics of many-fermion systems. A real-time simulation based on the time-dependent density functional theory (TDDFT) is the center of our methodology. The TDDFT was originally developed in the field of theoretical nuclear physics to describe low-energy nuclear collision phenomena. It also describes successfully the response properties of atomic nuclei. We have recently invented an efficient method to calculate responses of atomic nuclei to an external perturbation, and have undertaken a project to construct systematic database of nuclear response extending whole nuclear chart. Responses at high excitation energies provide knowledge on nuclear matter, while responses around neutron emission threshold provide important knowledge for understanding rapid-processes in nucleosynthesis.

Fig.1 Systematic calculation for nuclear response

## Nuclear methods in other field

The theoretical nuclear theory group is also active to apply TDDFT to electron dynamics in matters, since we pioneered the method of real-time electron dynamics simulation. The TDDFT is now widely recognized as an accurate and convenient tool to describe electronic excitations in molecules. The real-time electron dynamics simulation is an efficient alternative to methods in quantum chemistry. It is especially useful calculating responses for a whole spectral region including photoionization. We are currently developing a method of first-principles simulation to describe interaction of strong laser pulse with crystalline solid. It provides a unified description of a variety of laser-matter interaction, including dielectric function, coherent phonon generation, and optical dielectric breakdown in dielectrics.

Fig.2 Real-time electron dynamics simulation

### Web sites

Theoretical Nuclear Physics Laboratory (Japanese)