セミナー(Seminar) 2020.12.11: Dr Cheng-Jun Xia (Zhejiang University, China)

2020年12月9日 | 新着情報

Lecturer: Cheng-Jun Xia (Zhejiang University)
Date/Time: 15:30, December 11 (Fri), 2020
Place: Meeting Room A in Center for Computational Sciences, together with Zoom.
Title: Nuclear pasta structures and symmetry energy
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 three-dimensional geometry with reflection symmetry. The numerical accuracy and efficiency are improved by expanding the mean fields according to fast cosine transformation and considering only one octant of the unit cell. The effect of finite cell size is treated carefully by searching for the optimum cell size. Typical pasta structures (droplet, rod, slab, tube, and bubble) arranged in various crystalline configurations are obtained for both fixed proton fractions and β-equilibration. It is found that the properties of droplets/bubbles are similar in body-centered cubic (BCC) and face-centered cubic (FCC) lattices, where the FCC lattice generally becomes more stable than BCC lattice as density increases. For the rod/tube phases, the honeycomb lattice is always more stable than the simple one. By introducing an ω-ρ cross coupling term, we further examine the pasta structures with a smaller slope of symmetry energy L = 41.34 MeV, which predicts larger onset densities for core-crust transition and non-spherical nuclei. Such a variation due to the reduction of L is expected to have impacts on various properties in neutron stars, supernova dynamics, and binary neutron star mergers.

This seminar is given in English. Contact the organizer (Kai Wen) to obtain the Zoom link.

セミナー(Seminar) 2020.11.20: Dr Simin Wang (MSU, USA)

2020年11月10日 | 新着情報

Lecturer: Simin WANG (MSU)
Date/Time: 14:00, November 20 (Fri), 2020
Place: Meeting Room A in Center for Computational Sciences, together with Zoom.
Title: Study of the two-proton radioactivity
Abstract: Two-proton (2p) radioactivity is a rare decay mode found in a few very proton-rich isotopes. The 2p decay width and properties of emitted protons carry invaluable information on nuclear structure in the presence of a low-lying proton continuum. For example, in mid-heavy nuclei, the measured 2p decay of 67Kr turned out to be unexpectedly fast [1]. And more recently, as the mirror of the halo nucleus 11Li, 11O was observed for the first time with a very broad peak [2]. To understand these exotic phenomena, we apply the Gamow coupled-channel method, which describes structure and decays of three-body systems within one coherent theoretical framework by utilizing resonant and scattering states in eigenfunction expansion [3]. The calculated lifetimes, angular correlations, and other properties indicate that the nuclear inner structure and continuum effect play a significant role in the decay process [2,3]. Moreover, to provide insights into the impact of nucleonic superfluidity on two-nucleon decay processes, we are developing a novel time-dependent approach, which will allow us to consider different experimental initial-setups and directly compare the predictions and data without losing structural information. With this new approach, we reveal the different dynamics of 2p and 2n decays.
[References]
[1] Goigoux et al., Phys. Rev. Lett. 117, 162501 (2016).
[2] T.B. Webb et al., Phys. Rev. Lett. 122, 122501 (2019).
[3] S. M. Wang and W. Nazarewicz, Phys. Rev. Lett. 120, 212502 (2018).

This seminar is given in English. Contact the organizer (Kai Wen) to obtain the Zoom link.

Young Faculty Award in University of Tsukuba (Dr Shunsuke Sato); 筑波大学若手教員奨励賞受賞（佐藤駿丞）

2020年10月26日 | 新着情報

Dr Shunsuke Sato, International Tenure-Track Assistant Professor, has been awarded Young Faculty Award in University of Tsukuba, for his outstanding contributions to increasing research activities.

本学の研究力向上に貢献し業績をあげた若手教員を顕彰する「筑波大学若手教員奨励事業」において、国際テニュアトラック助教・佐藤駿丞さんが令和2年度若手教員奨励賞を受賞しました。

セミナー(Seminar) 2020.10.23: Dr Toshimi Suda (Tohoku Univ.)

2020年10月16日 | 新着情報

Lecturer: Toshimi SUDA (Tohoku University) [東北大学　電子光理学研究センター　須田利美]
Date/Time: 14:00, October 23 (Fri), 2020
Place: Meeting Room A in Center for Computational Sciences, together with Zoom
Title: Electron scattering for structure studies of proton and exotic nuclei
Abstract: 本セミナーでは、東北大学と理化学研究所の電子加速器を利用して進めている電子散乱による陽子と短寿命不安定核の構造研究について紹介します。
１）陽子電荷半径 : ULQ2 (Ultra Low Q2)＠東北大電子光理学研究センター
史上最低エネルギー（Ee = 20 – 60 MeV）の電子・陽子弾性散乱から、最も信頼度の高い陽子電荷半径を決定します。ここ数年、科研費により電子光理学研究センター内に新しくビームラインと２連の散乱電子スペクトロメータを建設しています。本研究は、「陽子半径パズル」と呼ばれる陽子電荷半径に関する混乱に決着をつけ、正しい陽子電荷半径の決定が目標です [1,2]。セミナーでは、陽子半径パズル、ULQ2 計画そしてコミッショニングの現状と今後の展望を紹介します。
２）短寿命不安定核の電荷密度分布 : SCRIT@理化学研究所 RIBF
　私たちは、前例のない電子散乱による短寿命不安定核研究を可能にするSCRIT電子散乱施設を理化学研究所 RIビームファクトリーに建設し稼働を開始させました [3]。SCRIT 施設の現場と今後の研究展望について紹介します。
　電子弾性散乱で決定される電荷密度分布は主として陽子分布の情報を与えますが、電荷密度分布の４次モーメントから核内中性子分布の平均二乗半径が決定できる可能性が理論的に指摘されました [4,5]。この指摘を受けて、原子核構造研究に最適な電子散乱で不安定核の陽子と中性子分布を同時決定する可能性の検討を進めています。セミナーではこの可能性についても皆さんと議論したいと考えています。
【参考文献】
1. “Measurement of proton charge radius by low-energy electron scattering.”, T. Suda et al., J. Part. Acc. Soc. Japan 15 (2018) 52-59.
2. 「極運動量移行領域での電子・陽子弾性散乱による陽子電荷半径の精密決定.」須田利美、塚田暁、　原子核研究 61 (2017) 87.
3. “Prospects for electron scattering on unstable exotic nuclei.”, T. Suda and H. Simon, Prog. Part. Nucl. Phys. 96 (2017) 1.
4. “The n-th order moment of the nuclear charge density and contribution from neutron”, H. Kurasawa and T. Suzuki, Prog. Theor. Exp. Phys. 11 (2019) 113D01
5. “The mean square radius of the neutron distribution and the skin thickness derived from electron scattering.”, H. Kurasawa, T. Suda and T. Suzuki, arXiv 2009.00759

This seminar is given in Japanese.

新メンバー：尾﨑さん、小澤さん、土田さん New members: Ozaki, Ozawa, and Tsuchida

2020年4月10日 | 新着情報

New graduate students in the Master course, Ozaki and Ozawa, and a new undergraduate student, Tsuchida, have joined our group.

大学院生（M1）の尾﨑さんと小澤さん、4年生の土田さんが研究室のメンバーに加わりました。

International external review (2020.2.19-21)

2020年2月14日 | 新着情報

The external review of Center for  Computational Sciences (CCS) will take place in February 19-21, 2020. Our staff members are associated with both Division of Nuclear Physics  (T. Nakatsukasa [Division Head], Y. Hashimoto, N. Hinohara) and Division of Quantum Condensed Matter Physics (K. Yabana [Division Head], S. Sato).

計算科学研究センター（CCS）の国際外部評価が2020年2月19-21日に行われます。当研究室の教員は、原子核物理部門（中務[部門長]、橋本、日野原）と量子物性部門（矢花[部門長]、佐藤）に所属しており、外部評価を受けることになっています。

セミナー(Seminar) 2019.12.13: Dr Shuichiro Ebata (Saitama)

2019年12月10日 | 新着情報

We have a seminar as follows:

Lecturer: Shuichiro EBATA (Saitama University)

Date: December 13 (Fri), 2019

Place: Meeting Room B in Center for Computational Sciences

Tittle: Mean-field studies for nuclear fission and fusion

Abstract: Nuclear fission and fusion are fundamental phenomena in nuclear physics, and so far, many studies have been actively carried out. With the developments of effective interaction and computational resources, it has become realistic to approach theses phenomena by the theoretical calculations. We have developed the method based on mean-field theories to describe fission and fusion. In this presentation, we will show the charge polarization of fission products deduced by the constraint Skyrme Hartree-Fock+BCS model represented in the three-dimensional Cartesian coordinates. And the procedure to describe the superheavy element synthesis using the canonical-basis time-dependent Hartree-Fock-Bogoliubov theory is introduced.

江幡さん　埼玉大学・テニュアトラック助教に着任、Dr Ebata took up a tenure-track Ass. Prof. in Saitama Univ.

2019年12月1日 | 新着情報

Dr Shuichiro Ebata, who received PhD in our group in March 2011, has taken up a tenure-track assistant professor position in Saitama University. After his PhD, he has been continuing his researches in nuclear theory and nuclear engineering at various places including Center for Nuclear Study, University of Tokyo, Hokkaido University, and Tokyo Institute of Technology.

当研究室の出身で2012年3月に博士（理学）の学位を取得した江幡修一郎さんが、2019年12月から埼玉大学の助教（テニュアトラック）に着任しました。江幡さんは、筑波大学で学位を取得後、東京大学原子核科学研究センター、北海道大学、東京工業大学等でポスドク研究員として原子核理論、および原子力工学に関わる研究を行なってきています。

Young Scientist Award of the Physical Society of Japan (Dr Shunsuke Sato); 第14回日本物理学会若手奨励賞（佐藤駿丞）

2019年11月6日 | 新着情報

Dr Shunsuke Sato, International Tenure-Track Assistant Professor, who was a PhD student in our group, will be awarded Young Scientist Award of the Physical Society of Japan in 2020 (Division 5, Optical properties of condensed matter), for his theoretical researches on attosecond electron dynamics in solids.

当研究室出身で博士号を取得し、現在国際テニュアトラック助教である佐藤さんが、固体におけるアト秒電子ダイナミクスの理論的研究における業績で、第14回日本物理学会若手奨励賞（領域5）を受賞することが決定しました。

セミナー(Seminar) 2019.10.25: Dr Takeru Yokota (KEK)

2019年9月19日 | 新着情報

We have a seminar by Dr Takeru Yokota, KEK, on October 25th, 2019. The seminar is given in English.

  • Lecturer: Dr Takeru YOKOTA (KEK)
  • Title: Functional-renormalization-group aided density functional theory
  • Time/Date: 13:45-, October 25, 2019
  • Place: Meeting Room B, Center for Computational Sciences (1F), University of Tsukuba
  • Abstract: The functional-renormalization-group aided density functional theory (FRG-DFT) is an attempt to microscopically formulate the density functional theory borrowing ideas from the functional renormalization group. This method is expected to become a powerful approach for the fundamental problems of the density functional theory such as the microscopic determination of the energy density functional and the analyses of excited states involving the large-amplitude collective dynamics.
    In this talk, I will introduce the FRG-DFT and present our works, which includes the formulation for continuum homogeneous matters [1], the analysis of the ground and excited states of a one-dimensional fermionic matter [1, 2], and the application to the two-dimensional homogeneous electron gas [3]. I may also discuss our recent works on the application to systems with arbitrary spin polarization and superfluidity.
    [1] T. Yokota, K. Yoshida, and T. Kunihiro, Phys. Rev. C 99, 024302 (2019).
    [2] T. Yokota, K. Yoshida, and T. Kunihiro, Prog. Theor. Exp. Phys (2019) 011D01.
    [3] T. Yokota and T. Naito, Phys. Rev. B 99, 115106 (2019).