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欣逢杨振宁先生百年诞辰, 已有不少文章总结了杨先生对当代物理学发展的重要科学影响. 笔者认为, 作为当代最伟大的理论物理学家之一, 杨先生不仅以诸多具体的科学贡献推动了当代物理学革命性的进步, 而且其独特的科学风格在国际学术界独树一帜, 其学术思想更是深邃隽永、对中国和世界的物理学发展有长远的启发作用. 笔者将结合学习杨振宁科学思想的体会, 联系自己在理论物理研究方面的科学实践(包括在1992—1994年跟随杨先生对量子开系统、超导相变和冷原子物理方面的探索), 对当代理论物理发展趋势提出一些个人的看法. 文章将通过具体实例, 阐述为什么要做“美或有用”的理论物理; 为什么基本物理的理论在一段时间内可以与直接的实验验证保持距离? 对于后者, 本文还从科学方法论(哲学)的角度就理论预言与实验证实的关系进行较为深入的讨论. 着眼于“有用”的理论物理-应用理论物理, 笔者强调了国家需求驱动的科学研究与自由探索一样, 也会导致基础物理的重要突破.On the occasion of the centennial birthday of Mr. Chen-Ning Yang, many articles have summarized his important scientific influences on the development of contemporary physics. The author thinks that, as one of the greatest theoretical physicists, Mr. Yang in many scientific contributions has promoted the revolutionary progress of physics, and his unique style of science with deep and meaningful thoughts in academia has a long-term inspiration on developments of physics. Learning from Chen-Ning Yang's scientific thoughts, the author will put forward some personal opinions on the development trend of theoretical physics with his own experiences in researching theoretical physics for 30 years, e.g., studies of quantum open system, superconducting phase transition and cold atom physics by following Mr. Yang in Stony Brook from 1992 to 1994. This article will elaborate why it is important to pursue “beautiful or useful” theoretical physics through some concrete illustrations; Why could the good theories in fundamental physics be kept at a distance from experiments for some time? For the latter, this article also argues the relationship between theoretical prediction and experimental confirmation from the perspective of scientific methodology (philosophy). Focusing on “useful” theoretical physics-the applied theoretical physics, the author emphasizes that scientific research driven by the national demand, as well as free exploration, can also lead to important breakthroughs in fundamental physics.
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Keywords:
- Chen-Ning Yang /
- theoretical physics /
- development trend /
- scientific style
[1] 国家自然科学基金委员会, 中国科学院 2009 未来10年中国学科发展战略·物理学 (北京: 科学出版社) 第1−2页
National Natural Science Foundation of China, Chinese Academy of Sciences Chinese 2009 Discipline Development Strategy for the next 10 Years-Physics (Beijing: Science Press) pp1−2 (in Chinese)
[2] 理论物理专款学术领导小组 2013 发展理论物理促进学科交叉—国家自然科学基金理论物理专款20周年纪念文集 (北京: 科学出版社) 第18−54页
Academic leading group of the special funds for theoretical physics in the National Natural Science Foundation of China 2013 Summary and Perspective of the ten-year Work on the Special Funds for Theoretical Physics in the National Natural Science Foundation of China (Beijing: Science Press) pp18−54 (in Chinese)
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Weinberg S (translated by Li Y) 2018 Dreams of a Final Theory (Changsha: Hunan Science & Technology Press) (in Chinese)
[4] S. 温伯格 (黄艳华, 江向东 译) 2004 仰望苍穹: 科学反击文化敌手(上海: 上海科技教育出版社)
Weinberg S (translated by Huang Y H, Jiang X D) 2004 Facing Up: Science and Its Cultural Adversaries (Shanghai: Shanghai Scientific and Technological Education Publishing House) (in Chinese)
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Yang C N 2018 Shu Guang Ji (Beijing: SDX Joint Publishing Company) pp1−7 (in Chinese)
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Yang C N, Weng F 2018 Chen Xi Ji (Beijing: China Commerce and Trade Press) pp3−19 (in Chinese)
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图 1 杨振宁的规范场论通过对称性自发破缺机制 (等价于他的非对角长程序理论), 本质上统一了理论物理学两大方面—还原论和演生论
Fig. 1. By the spontaneous symmetry breaking mechanism (equivalent to his theory of off-diagonal long-range order), Chen-Ning Yang’s gauge field theory essentially unifies the two major aspects of theoretical physics—reductionism and emergence theory.
图 2 数学物理在中国的发展和相关人才的成长
Fig. 2. The development of mathematical physics in China and the growth of relevant talents.
图 3 1957年李-杨的理论预言影响了测量μ子到正负电子衰变的分支比的误差处理: 测量每一次实验的中值都落在前一次实验误差范围内, 10年后逼近预言3/4而稳定
Fig. 3. Li and Yang’s theoretical prediction in 1957 had affected the error processing in measurement about the branching ratio of decays of μ to positron and electron: the median value of each experiment fell within the error range of the previous experiments, and after 10 years, it approached and became stale on the predicted value of 3/4.
图 4 实际纳米线-超导紧邻系统-Kitaev模型与Majorana零模实验观察 (a)实际系统(上)和期望约化到的理想Kitaev模型的相图拓扑结构(下); (b)更高阶微扰论方法预言的相图—随磁场变化由开到闭; (c)微分电导随磁场变化的严格计算
Fig. 4. Experimental observations about Majorana zero modes and the Kitaev model for the practical system of nanowire proximity-coupled superconductor: (a) The practical nanowire-superconductor system (top) and the topological phase diagram determined by the ideal Kitaev model(down); (b) the topological phase diagram predicted by the approach based on higher-order perturbation, which goes from open hyperbolic to closed triangle region as the magnetic field changes from weak to strong; (c) Exact calculation of differential conductance with change of the magnetic field.
图 5 证实“理论”实验的分级(实际物理-模型-实验的“距离”决定了“实验证实”工作的好坏) (a)模型预言覆盖了实际系统的全部物理, 实验正好证实了模型预言; (b)虽然模型预言覆盖了实际系统理论结果的全部, 但实验只是证实了基于模型预言的一部分; (c)模型预言覆盖了关于实际系统理论结果的一部分, 实验也只是证实了“模型预言”; (d)模型预言不能覆盖实际系统物理的全部, 实验也只是符合模型部分不准确预言, 证实与否甚至与实际系统无关
Fig. 5. Ranking of experiments that confirm “theory” (the “distances” between the actual physics and model (experiments) determine how well the “experimental verification” works): (a) The model based prediction covers all the physics of the actual system, and the experiment just confirms the model based prediction; (b) Although the model based prediction covers all the theoretical results about the actual systems, the experiment only confirms part of the model based predictions; (c) The model based prediction covers part of theoretical results about the actual system, and the experiment only confirms “model based predictions”; (d) The model based prediction cannot cover all the physics of the actual system, and the experiment only conforms some inaccurate predictions from the model, and even whether it is confirmed or not even has nothing to do with the actual system.
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[1] 国家自然科学基金委员会, 中国科学院 2009 未来10年中国学科发展战略·物理学 (北京: 科学出版社) 第1−2页
National Natural Science Foundation of China, Chinese Academy of Sciences Chinese 2009 Discipline Development Strategy for the next 10 Years-Physics (Beijing: Science Press) pp1−2 (in Chinese)
[2] 理论物理专款学术领导小组 2013 发展理论物理促进学科交叉—国家自然科学基金理论物理专款20周年纪念文集 (北京: 科学出版社) 第18−54页
Academic leading group of the special funds for theoretical physics in the National Natural Science Foundation of China 2013 Summary and Perspective of the ten-year Work on the Special Funds for Theoretical Physics in the National Natural Science Foundation of China (Beijing: Science Press) pp18−54 (in Chinese)
[3] S. 温伯格(李泳译) 2018 终极理论之梦 (长沙: 湖南科学技术出版社)
Weinberg S (translated by Li Y) 2018 Dreams of a Final Theory (Changsha: Hunan Science & Technology Press) (in Chinese)
[4] S. 温伯格 (黄艳华, 江向东 译) 2004 仰望苍穹: 科学反击文化敌手(上海: 上海科技教育出版社)
Weinberg S (translated by Huang Y H, Jiang X D) 2004 Facing Up: Science and Its Cultural Adversaries (Shanghai: Shanghai Scientific and Technological Education Publishing House) (in Chinese)
[5] Weisskopf V F 1967 Phys. Today 20 23
[6] Anderson P W 1977 Science 177 393
[7] 张广铭, 于渌 2010 物理 39 543
Zhang G M, Yu L 2010 Physics 39 543
[8] 郝柏林 2009 负戟吟啸录 (新加坡: 八方文化创作室) 第98页
Hao B L 2009 Fu Ji Yin Xiao Lu (Singapore: Global Publishing) p98 (in Chinese)
[9] 杨振宁 1997 二十一世纪 40 71
Yang C N 1997 Twenty-First Century 40 71
[10] 杨振宁 2015 中国美术馆 3 34
Yang C N 2015 NAMOC 3 34
[11] Song C D http://www.inewsweek.cn/people/2021-05-31/12699.shtml [2021-10-26]
[12] Yang C N 1962 Rev. Mod. Phys. 34 694
Google Scholar
[13] Yang C N 1947 Phys. Rev. 72 874
Google Scholar
[14] Yang C N 1980 Phys. Today 33 42
[15] 孙昌璞 2021 中国科学院院刊 36 296
Sun C P 2021 Bull. Chin. Academ. Sci. 36 296
[16] 庆承瑞, 何祚庥 1996 现代物理知识 1 29
Qing C R, He Z X 1996 Mod. Phys. 1 29
[17] Everett H 1957 Rev. Mod. Phys. 29 454
Google Scholar
[18] 孙昌璞 2017 物理 46 481
Google Scholar
Sun C P 2017 Physics 46 481
Google Scholar
[19] Li S W, Cai C Y, Liu X F, Sun C P 2018 Found. Phys. 48 654
Google Scholar
[20] Qiao G J, Li S W, Sun C P 2021 arXiv 2112: 13568
[21] [22] 杨振宁 2018 曙光集 (北京: 三联出版社) 第1−7页
Yang C N 2018 Shu Guang Ji (Beijing: SDX Joint Publishing Company) pp1−7 (in Chinese)
[23] 杨振宁, 翁帆 2018 晨曦集 (北京: 商务出版社) 第3−19页
Yang C N, Weng F 2018 Chen Xi Ji (Beijing: China Commerce and Trade Press) pp3−19 (in Chinese)
[24] 张慧琴, 王鑫, 王旭, 孙昌璞 2021 中国工程科学 23 8
Zhang H Q, Wang X, Wang X, Sun C P 2021 Strateg. CAE 23 8
[25] 王旭, 孙昌璞 2019 物理 48 1
Google Scholar
Wang X, Sun C P 2019 Physics 48 1
Google Scholar
[26] http://blog.Science net.cn/blog-528739-1135541.html
[27] Du Y M. Ma Y H, Wei F Y, Guan X F, Sun C P 2020 Phys. Rev. E 101 012106
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