九大原子核セミナー

2020年11月13日(金) 16:30〜

講師：Cheng-Jun Xia 氏 (Zhejiang University, Ningbo Institute of Technology)
演題：Nuclear “pasta” structures and symmetry energy
場所：※オンラインセミナー

概要(Abstract)： In the framework of the relativistic mean field model with Thomas-Fermi approximation, we study the structures of low density nuclear matter in a fully three-dimensional geometry. Typical pasta structures (droplet, rod, slab, tube, and bubble) arranged in various crystalline configurations are obtained for both fixed proton fraction and cold catalyzed matter. By introducing an ω-ρ cross coupling term, we further examine the pasta structures with smaller symmetry energy slope L = 41.34 MeV, which is consistent with various constrains from nuclear physics and pulsar observations.

2020年11月13日(金) 16:30〜

講師：Tetsuo Hyodo 氏 (Tokyo Metropolitan University)
演題：Lambda(1405) as a hadronic molecule
場所：※オンラインセミナー

概要(Abstract)： Hadronic molecules are the new form of matter induced by the strong interaction.
However, identification of the hadronic molecules involves several subtle difficulties such as the model dependence and the interpretation of the resonance wave function. To overcome these difficulties, we use the compositeness to characterize the internal structure of hadrons, and generalize the weak-binding relation for unstable resonances. It is quantitatively shown that the structure of the $\Lambda(1405)$ resonance is dominated by the molecular state of an antikaon and a nucleon.

2020年11月16日(月) 15:00〜17:30

講師：土岐 博 氏 (大阪大学)
演題：原子核におけるパイ中間子の役割と私が描く核物理
場所：九州大学伊都キャンパス
ウエスト1号館2階 B-212講義室 (W1-B-212)
※オンライン形式でも参加可能

概要(Abstract)： パイ中間子は核子間の相互作用の中長距離を支配している。カイラル対称性の破れから生じるパイ中間子は擬スカラー粒子であり、核子間に強いテンソル力を生じる。桁違いに大きなテンソル力は強いテンソル相関を生み出し、大きく束縛エネルギーに寄与する。テンソル最適化した反対称化分子動力学法(TOAMD)による計算結果で核物理における重要さを定量的に議論する。さらに、パイ中間子はバリオンの励起状態であるデルタ粒子と強く結合する。核子間の３体力を生み出す原動力になっているが、３体力でとどまる保証はない。次のステップではデルタを陽に含む可能性を考える。私の描く将来の核物理である。

2020年7月31日(金) 16:30〜

講師：鈴木　渓 氏 (JAEA, 日本原子力研究開発機構)
演題：QCD Casimir effect for exploring chiral partners of hadrons
場所：※オンラインセミナー

概要(Abstract)： The original Casimir effect is a zero-point energy shift induced by two parallel plates, which is a perturbative phenomenon in the QED vacuum (essentially, photon fields). On the other hand, in the QCD vacuum including quarks and gluons (and also hadrons), the Casimir effect should be affected by the nonperturbative properties such as the spontaneous chiral symmetry breaking, color confinement, and instantons. The "Casimir effect" in QCD is still not experimentally observed, but recently similar phenomena were observed from lattice pure Yang-Mills simulations.


In this talk, I will discuss our recent studies about the relation between the Casimir effect in QCD and the chiral partner structures of hadrons such as nucleons [1] and D mesons [2]. In addition, I will discuss the Casimir effect for lattice fermions [3], which will be measured in lattice simulations and strongly correlated electron systems.

[1] T. Ishikawa, K. Nakayama, and K. Suzuki, Phys.Rev.D99, 054010 (2019).
[2] T. Ishikawa, K. Nakayama, D. Suenaga, and K. Suzuki, Phys.Rev.D100, 034016 (2019).
[3] T. Ishikawa, K. Nakayama, and K. Suzuki, arXiv:2005.10758.

2020年7月17日(金) 15:00〜

講師：Jinniu Hu 氏 (南開大学)
演題：Properties of neutron star from ab initio calculation to machine learning
場所：※オンラインセミナー

概要(Abstract)： The golden age of neutron-star physics has come with rapid developments of astronomical techniques. The observation of gravitational wave as GW170817 event from binary neutron-star merger opens the multi-messenger astronomy. But, a 2.6 solar mass compact object in GW190814 observed recently also took a great challenge to present nuclear many-body theory. We investigated the properties of neutron star in the frame work of a relativistic ab initio method, i.e. relativistic Brueckner-Hartree-Fock (RBHF) theory with high-precision charge-dependent relativistic nucleon-nucleon (NN) potentials. All of the results obtained from present calculations only with two-body NN potentials completely satisfy various constraints from recent astronomical observations of massive neutron stars, gravitational wave detection (GW170817), and mass-radius simultaneous measurement (NICER).


Furthermore, we also try to produce a complete equations of state (EOS) of neutron star from crust to core with machine learning method and the mass-radius observations of available 14 neutron stars. A five layer artificial neural network (ANN) system was designed, where the observations of neutron star and EOS are regarded as the input and output of ANN system, respectively. 100 EOSs were obtained with millions of training data. These EOSs cannot only generate reasonable mass-radius relations of neutron star at intermediate mass region but also generate massive compact stars more than 2.6 solar mass.