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Abstract:
Neutrino physics research is related to nuclear physics in many ways. When we study (anti)neutrinos produced by b decay (whether in supernovae or reactors), the decay rate depends largely on the structure of the parent and daughter nuclei described by the nuclear wave function. When we study neutrino-nuclear reactions, such as in the np process and n process of nucleosynthesis, cross-section calculations require accurate knowledge of the nuclear wave function. When the nuclear wave function is coupled with appropriate quantum mechanical operators, nuclear matrix elements are formed, which are the core physical quantity representing the decay rates and neutrino reaction cross-sections.
Unfortunately, existing nuclear database for neutrino study (such as data of b decay rates and reaction cross-sections) is far from complete and accurate, and theories to extract neutrino spectrum need to be improved. Those used to understand the reactor antineutrino anomaly are such examples.
Theoretical calculation to obtain nuclear wavefunction is a very complicated many-body problem. Traditional nuclear models can be divided into two categories, namely, the spherical shell model (SM) based on diagonalization and the mean field (MF) method based on the variational principle. The former is considered an exact model within the restricted model space. However, space limitations hinder the application of SM in heavy nuclei and highly excited states. The latter is an approximate method, usually study near ground states rather than excited states. Furthermore, MF models are not suitable for computing general observables due to not well-defined wavefunctions.
There is an urgent need for finding breakthroughs in nuclear theory. This talk introduces the Projected Shell Model (PSM) which is currently the only model that takes advantages of both SM and MF. With deformed heavy nuclei as examples, we demonstrate how eigenvalue problems, H |Ψ> = E |Ψ>, can be solved to obtain well-defined wavefunctions. Recent examples in application in nuclear science and astrophysical research and potential future applications will be presented.
About the speaker:
孙扬教授：
上海交通大学物理与天文学院特聘教授，中国物理学会吴有训奖获得者。1985 年获阿登纳基金会资助赴德国留学, 1991 年慕尼黑工业大学理论核物理专业获博士学位；其后多年在欧洲和美国工作, 包括西班牙马德里自治大学、美国橡树岭国家实验室、田纳西大学及圣母大学；2007年起受聘于上海交通大学；兼任中科院兰州近代物理所、北京中国原子能研究院兼职教授。
主要从事原子核结构理论以及与原子核有关的各类交叉研究工作, 是投影壳模型的创始人之一，并独立发展了该模型，使该模型在原子核高激发态、同核异能态、原子核相变、超重元素结构、天体核合成等研究领域发挥了重要应用。近年来的主要兴趣集中在与天体核过程有关的核结构与反应方面，研究内容涉及到高温、高密度、丰质子、丰中子状态下的核结构；天体环境下的核结构和核过程；宇宙中的元素合成机制；核物理、粒子物理、和天体物理中的弱相互作用；强关联多体量子体系的集体运动和相变等。
合作发表学术论文300余篇，其中包括在《自然》、《自然-物理》、《物理评论通讯》等学术刊物上。著有《天文学教程（上、下册）》(上海交通大学出版社)、《Symmetry, Broken Symmetry, and Topology in Modern Physics》(Cambridge University Press)。多次参与国际核物理系列大会如“Nuclear Structure”以及“Captured Gamma-ray Spectroscopy（CGS）”的国际顾问委员会，并曾于2017年在上海交通大学举办了CGS16国际核物理大会。
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