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高等原子核理论 Advanced Nuclear Theory

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1 高等原子核理论 Advanced Nuclear Theory
2017/4/13 高等原子核理论 Advanced Nuclear Theory 北京大学物理学院 技术物理系 • 裴俊琛 Junchen Pei, School of Physics, Peking University 2014.9, Beijing Progress

2 Advanced Nuclear Theory----J.C. Pei
2017/4/13 Contents Background and developments Earlier Nuclear models Ab inito and Shell Model Density Functional Theory Nuclear forces Nuclear superfluidity Symmetries and collective motion DFT extensions Reaction Theory Advanced Nuclear Theory----J.C. Pei Progress

3 Challenges in nuclear physics
2017/4/13 Challenges in nuclear physics Superheavies RNB facilities offer unprecedented opportunities to access unstable nuclei Progress In Computing Nuclei and Cold Atoms Progress

4 RNB facilities around the world
FRIB FAIR RIBF SPAIRL-II Argonne, HRIBF, HIRFL-CSR, Why RNB? Advanced Nuclear Theory----J.C. Pei

5 How to study nuclear physics
Reaction-observation-nuclear models Different reaction mechanism Observations: decays, fragments, emissions  structures Models: many-body Hamilton and nuclear forces Advanced Nuclear Theory----J.C. Pei

6 Advanced Nuclear Theory----J.C. Pei
Background Nuclear theory at different resolutions/precision, with different degrees of freedom Effective nuclear forces associated nuclear many-body problems Multi-Physics overlaps and observables in different aspects Advanced Nuclear Theory----J.C. Pei

7 本科生—研究生 本科:书本上基础知识学习, 主要是为了考试
研究生:主要目的是研究,学习为了研究和解决问题,创造新知识,职业训练(独立科研的能力)

8 导师---学生 导师: 提供平台, 建议方向,教授方法, 解决难题 学生: 实现物理想法,团队合作,自我提升
导师---学生之间interface: 沟通,信任 不愤不启,不悱不发 《论语》

9 魔鬼在细节中 不要Assume你的结果:结果没有好坏, unexpected往往才是有价值的! 时间在点滴之中

10 物理 <------格物 创新 对比 变化 理论与实验 观测量直接对比 Pesudo间接对比 实验与预言 不同模型 不同方法
新的理论,思想 新的Hamiltonian 新的观测量 新的模型方法 新的实验和理论精度 新的参数 对比 变化 系统性对比发现变化 归纳已知外推未知 创新引起变化 关于物理的思考---裴俊琛 2013 PKU

11 核物理的前景 物质结构不同的层次划分: 超级计算机的发展: petaflop(天河1号2.6-天河2号38)—exaflop
宇观,宏观,分子,原子,核,核子,夸克 不同层次的都有自身特点和问题并且不可替代 对交叉的物理问题有贡献:量子多体,核天体,QCD, 甚至生物,金融等 超级计算机的发展: petaflop(天河1号2.6-天河2号38)—exaflop FRIB (Facility for Rare Isotope Beams) 应用:能源,信息,医疗……

12 2017/4/13 原子核理论的发展与前沿 The Developments and Frontiers of Theoretical Nuclear Physics 北京大学物理学院 • 裴俊琛 Junchen Pei, School of Physics, Peking University 2013.9 Progress

13 Advanced Nuclear Theory----J.C. Pei
Outline Nuclear structure: macroscopic and microscopic perspectives Modern nuclear theory and supercomputing Nuclear theory and multi-disciplinary subjects Summary and outlook Advanced Nuclear Theory----J.C. Pei

14 Nuclear liquid drop model and fission
Nuclear liquid drop model of Fission: the competition between Coulomb and surface tension (1939), By Bohr and Wheeler Fission calculations on the first computer Eniac (1946), By Frankel (1947) 𝐸= 𝐸 𝑣𝑜𝑙𝑢𝑚𝑒 + 𝐸 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 + 𝐸 𝑠𝑦𝑚𝑚𝑒𝑡𝑟𝑦 +𝐸 𝐶𝑜𝑢𝑙𝑜𝑚𝑏 Problems: Can not explain the asymmetric fission Z>104 nuclei is unstable against spontaneous fission Magic numbers are missed (N=2, 8, 20, 28, 50, 82, 126, …..) Advanced Nuclear Theory----J.C. Pei

15 Explanation of liquid drop model
Fermi Gas model (non-interacting Fermions) 𝜑 𝑘 ∝ sin (𝑘 𝑥 x) sin (𝑘 𝑦 y) sin (𝑘 𝑧 z) Boundary condition (quantization) a 𝑘 𝑥(𝑦,𝑧) = 𝜋 𝑎 𝑛 𝑥 ( 𝑛 𝑦 , 𝑛 𝑧 ), 𝑛 𝑥 , 𝑛 𝑦 , 𝑛 𝑧 =1,2,3…. Eigen energy: 𝜀= ℎ 2 8𝑚 𝑎 2 (n 𝑥 2 +n 𝑦 2 +n 𝑧 2 ) Can explain the liquid drop model’s volume energy, surface energy, symmetry energy (due to different proton neutron numbers) Problem: magic numbers are missed Solution: we need nuclear interactions beyond Pauli principle Advanced Nuclear Theory----J.C. Pei

16 Magic numbers and shell effects
Magic numbers: Shell effects in finite Fermi systems Strong spin-orbit coupling in nuclei Mayer and Jenson (1949) + 𝑳∙𝑺 Magic numbers in atoms: 2, 10, 18, 32, 54, 86 Magic numbers in nuclei: 2, 8, 20, 28, 50, 82… General shell effects in quantum dots, droplets, alkali clusters, metal nanowires … Advanced Nuclear Theory----J.C. Pei

17 Macroscopic plus microscopic
Oscillations in level density (quantum effects), 1967 E = Eliquid-drop+ Eshell-correction Very successfully for describe nuclear bulk properties: mass, deformation, second minimum classical quantum Advanced Nuclear Theory----J.C. Pei

18 Nuclear many-body Hamiltonian
Generally: Problem: Can not be solved exactly for N>3 Solution: solving the many-body problem with a finite model space Solving the equation with different precision with different many-body techniques: ab inito, configuration interaction, density functional theory Advanced Nuclear Theory----J.C. Pei

19 Solving the Many-body problem
Start from the independent-particles Assume correlated many-body wavefunction can be expanded in the Fock space Fock space is the combination of various Hillbert spaces with different quasiparticles (A Hilbert space) A slater determinant Diagonalization: Advanced Nuclear Theory----J.C. Pei

20 Advanced Nuclear Theory----J.C. Pei
Modern Nuclear Forces Phenomenogical terms: Argonne v18 Meson exchange theory: CD-Bonn chiral perturbative theory: N3LO, three-body forces Lattice QCD calculations: residual interactions of quark clusters Effective nuclear forces: Renormalization: G-matrix, Vlow-k Advanced Nuclear Theory----J.C. Pei

21 Nuclear physics at multi-resolutions
Hadron physics resolution Ab inito CI Nuclear physics DFT Collective models Advanced Nuclear Theory----J.C. Pei

22 Overlaps are important
Advanced Nuclear Theory----J.C. Pei

23 Recent developments in nuclear theory
Drip-line of O isotopes Ab inito model study of 3-body forces Ab inito model study of nuclear reactions E Conclusion: 3-body force is important NCSM+RGM: provide important benchmark for reactions in astrophysics and NIF Exceptional long life time of C14 Advanced Nuclear Theory----J.C. Pei

24 Recent developments in nuclear theory
UNEDF project in US Universial Nuclear Energy Density Functional involve 19 institutions and 50 researchers Computer science, applied math, nuclear theorists Advanced Nuclear Theory----J.C. Pei

25 Challenges and opportunities
RIB facilities offer unprecedented opportunities to access unstable nuclei Superheavies Advanced Nuclear Theory----J.C. Pei

26 Latest nuclear landscape
From J. Erler et al., Nature, 486, 509(2012) Advanced Nuclear Theory----J.C. Pei

27 Advanced Nuclear Theory----J.C. Pei
Drip-line nuclei Continuum coupling effects Open quantum systems Advanced Nuclear Theory----J.C. Pei

28 Advanced Nuclear Theory----J.C. Pei
Halo structures Halos (1990s) Deformed Halo (Ne38)? Advanced Nuclear Theory----J.C. Pei

29 Shell structures at drip-lines
Advanced Nuclear Theory----J.C. Pei

30 New collective motion mode
Collective oscillation between core and the halo/skin Low energy E1 transition (pygmy resonances) Advanced Nuclear Theory----J.C. Pei

31 Treatment of Continuum
HFB includes generalized quasi-particle correlations; while BCS is a special quasiparticle transformation only on conjugate states. HFB G.S.: BCS G.S.: Deep bound states in BCS become quasiparticle resonances in HFB theory due to continuum coupling. HFB is superior to BCS for describing weakly-bound systems where continuum coupling becomes essential Box solution: bound states, continuum and embedded resonances are treated on an equal footing; L2 discretization leads to a very large configuration space(expensive) JP et al. PRC, 2011 Advanced Nuclear Theory----J.C. Pei

32 Answers to nuclear astrophysics
Advanced Nuclear Theory----J.C. Pei

33 Advanced Nuclear Theory----J.C. Pei
Neutron stars Related to nuclear equation of state A neutron star of 2.0 sun mass (2010) Pasta Advanced Nuclear Theory----J.C. Pei

34 Advanced Nuclear Theory----J.C. Pei
Nuclear mass limits How to chose the target, bombard, and the collision energy Hot fusion vs cold fusion? Advanced Nuclear Theory----J.C. Pei

35 Advanced Nuclear Theory----J.C. Pei
Nuclear spin limits The highest spin in the universe : 65hbar Advanced Nuclear Theory----J.C. Pei

36 Nuclear Temperature limits
Fission and neutron evaporation competition at high temperatures It becomes symmetric fission at high temperatures Advanced Nuclear Theory----J.C. Pei

37 Radioactive Beams Facilities
Great opportunities in 5 years Advanced Nuclear Theory----J.C. Pei

38 Advanced Nuclear Theory----J.C. Pei
Supercomputing Three legs of nuclear physics: experiments, theory, supercomputing Without supercomputing, ab inito, large scale DFT, continuum treatment are impossible New architures: multi-core+GPU (why: moving data is expensive) From Tianhe-1 to Tianhe-2, 20 times faster Advanced Nuclear Theory----J.C. Pei

39 Novel DFT infrastructure
Multi-resolution ADaptive Numerical Scientific Simulation CS infrastructure: Task-oriented: MPI, Global arrays, multi-threaded, futures (asynchronous computation), loadbalance 1. do A 2. do B if A 3. do C 4. do D if A ThreadPool WorldTaskQueue Main MPI 1. 3. 2. 4. Task dependencies: managed by Futures API Advanced Nuclear Theory----J.C. Pei

40 Dialogue with other physicists
Talk with condensed matter, cold atoms on many-body problems, superfluidity Talk to astrophysics on the evolution of universe, neutron stars Talk to high energy physics on testing standard model, AdS/CFT Advanced Nuclear Theory----J.C. Pei

41 Advanced Nuclear Theory----J.C. Pei
Summary and outlook The Nucleus is such a unique finite quantum system, presenting intriguing physics RIB facilities provide great opportunities and challenges for nuclear theory The development of modern nuclear theory is closed related to the capability of supercomputers Big collaborations, multi-disciplinary dialogues are very useful How about the future? Thanks for your attention! Advanced Nuclear Theory----J.C. Pei

42 Advanced Nuclear Theory----J.C. Pei


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