Yang Chen-Ning

Yang Chen-Ning (Template:Zh; (1 October 1922 – 18 October 2025); also known as C. N. Yang, Yang Zhenning,<ref>Template:Cite web</ref> or Franklin Yang<ref name="npbio">Template:Cite web</ref>) was a Chinese-American theoretical physicist who made significant contributions to statistical mechanics, integrable systems, gauge theory, particle physics and condensed matter physics.

Yang is known for his collaboration with Robert Mills in 1954 in developing non-abelian gauge theory, widely known as the Yang–Mills theory, which describes the nuclear forces in the Standard Model of particle physics.

Yang and Tsung-Dao Lee received the 1957 Nobel Prize in Physics<ref name="np">Template:Cite web</ref> for their work on parity non-conservation of the weak interaction, which was confirmed by the Wu experiment in 1956. The two proposed that the conservation of parity, a physical law observed to hold in all other physical processes, is violated in weak nuclear reactions – those nuclear processes that result in the emission of beta or alpha particles.

Early life and education

Yang was born in Hefei, Anhui, China, on 1 October 1922.<ref name="birthdate">Template:Cite web</ref> His mother was Luo Meng-hua and his father, Template:Ill (Template:Lang; 1896–1973), was a mathematician.<ref name=":0">Template:Cite journal</ref><ref>Template:Cite news</ref>

Yang attended elementary school and high school in Beijing, and in the autumn of 1937 his family moved to Hefei after the Japanese invaded China.<ref name="nytimes obit">Template:Cite news</ref> In 1938 they moved to Kunming,<ref name="nytimes obit" /> Yunnan, where National Southwestern Associated University was located. In the same year, as a second-year student, Yang passed the entrance examination and studied at National Southwestern Associated University. He received a Bachelor of Science in 1942,<ref name="npbio" /> with his thesis on the application of group theory to molecular spectra, under the supervision of Ta-You Wu.<ref name=":0" />

Yang continued to study graduate courses there for two years under the supervision of Wang Zhuxi (J.S. Wang), working on statistical mechanics. In 1944, he received a Master of Science from National Tsing Hua University, which had moved to Kunming during the Sino-Japanese War (1937–1945).<ref name="npbio" /> Yang was then awarded a scholarship from the Boxer Indemnity Scholarship Program, set up by the United States government using part of the money China had been forced to pay following the Boxer Rebellion.<ref>Template:Citation</ref> His departure for the United States was delayed for one year, during which time he taught in a middle school as a teacher and studied field theory.<ref name=":0" />

Yang entered the University of Chicago in January 1946 and studied with Edward Teller. He received a Doctor of Philosophy in 1948.<ref name="npbio" />

Career

Yang remained at the University of Chicago for a year as an assistant to Enrico Fermi.<ref name="nytimes obit" /> In 1949 he was invited to do his research at the Institute for Advanced Study in Princeton, New Jersey, where he began a period of fruitful collaboration with Tsung-Dao Lee.<ref name="nytimes obit" /> Lee and Yang published 32 papers together.<ref name="nytimes obit" /> He was made a permanent member of the Institute in 1952, and full professor in 1955. In 1963, Princeton University Press published his textbook, Elementary Particles. In 1965 he moved to Stony Brook University, where he was named the Albert Einstein Professor of Physics and the first director of the newly founded Institute for Theoretical Physics. Today this institute is known as the C. N. Yang Institute for Theoretical Physics.<ref name="npbio" /> Yang retired from Stony Brook University in 1999.<ref>Template:Cite web</ref>

Yang visited the Chinese mainland in 1971 for the first time after the thaw in China–US relations, and subsequently worked to help the Chinese physics community rebuild the research atmosphere,<ref name=":1">Template:Cite book</ref> which later eroded due to political movements during the Cultural Revolution.<ref name=":1" /> After retiring from Stony Brook, he returned to Beijing as an honorary director of Tsinghua University,<ref name=":1" /> where he was the first Huang Jibei-Lu Kaiqun Professor at the Center for Advanced Study (CASTU).<ref>Template:Cite web</ref> He was also one of the two Shaw Prize Founding Members and was a Distinguished Professor-at-Large at the Chinese University of Hong Kong.<ref>Template:Cite web</ref>

Yang helped to establish the Theoretical Physics Division at the Chern Institute of Mathematics in 1986 at the request of Shiing-Shen Chern who was serving as the inaugural director of the Institute at the time.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

Personal life and death

Yang married Tu Chih-li (Template:Zh), a teacher, in 1950; they had two sons and a daughter together. His father-in-law was the Kuomintang general Du Yuming. Tu died in October 2003. In January 2005, Yang married Weng Fan (Template:Zh), a university student. They met in 1995 at a physics seminar; the couple reestablished contact in February 2004. Yang called Weng, who was 54 years his junior, his "final blessing from God".<ref>Template:Cite news</ref>

Yang obtained U.S. citizenship during his research within the country. According to the state-run Xinhua News Agency, Yang said the decision was painful as his father never forgave him for that. According to Xinhua, he formally renounced his American citizenship in late 2015, while acknowledging the U.S. was a beautiful country that gave him good opportunities to study science.<ref>Template:Cite news</ref><ref>Template:Cite news</ref>

His son Guangnuo was a computer scientist.<ref>LA Times, 2022-03-01</ref> His second son Guangyu is an astronomer, and his daughter Youli is a doctor.<ref>Important Events in the Life of Chen Ning Yang (CNY)</ref>

Yang turned 100 on 1 October 2022,<ref>Template:Cite web</ref> and died in Beijing on 18 October 2025, at the age of 103.<ref name="dies">Template:Cite news</ref><ref name="nytimes obit" /> The day after the announcement of his death, people gathered and waited in line at Tsinghua University to pay tributes to Yang.<ref>Template:Cite web</ref>

Views on the CEPC

Yang is known for having opposed the construction of the Circular Electron Positron Collider (CEPC), a 100 km circumference particle collider in China that would study the Higgs boson.<ref name=":7">Template:Cite web</ref> He catalogued the project as "guess" work and without guaranteed results. Yang said that "even if they see something with the machine, it's not going to benefit the life of Chinese people any sooner."<ref name=":7" />

Academic achievements

Yang worked on statistical mechanics, condensed matter theory, particle physics and gauge theory/quantum field theory.

Various Nobel Prizes in Physics are based on Yang's work. At least 10 Nobel laureates in Physics cited Yang's work during their Nobel speech, this includes: Steven Weinberg (1979), Sheldon Glashow (1979), Martinus J. G. Veltman (1999), Gerard 't Hooft (1999), David Gross (1999), Yoichiro Nambu (2008), Makoto Kobayashi (2008), Toshihide Maskawa (2008), François Englert (2013) and Peter Higgs (2013).<ref name=":4" />

Early contributions

His first two papers (1944, 1945) were the result of his master thesis on statistical physics, supervised by J. S. Wang.<ref>Template:Cite journal</ref>

At the University of Chicago, Yang first spent twenty months working in an accelerator lab, but found he was not good at experimental physics and switched back to theory. His doctoral thesis was about an atomic beam apparatus for measuring the nuclear quadrupole resonance of sodium.<ref>Template:Cite book</ref>

Later, Yang worked on particle phenomenology; a well-known work was the Fermi–Yang model of 1949, treating the pion as a bound nucleon–antinucleon pair.<ref>Template:Cite book</ref>

Main contributions

Yang in 1957

Yang is well known for his 1953 collaboration with Robert Mills in developing non-abelian gauge theory, widely known as the Yang–Mills theory.<ref name=":2" /> The idea was generally conceived by Yang while the novice scientist Mills assisted him as Mills explained:<ref>Template:Cite book</ref>

During the academic year 1953–54, Yang was a visitor to Brookhaven National Laboratory ... I was at Brookhaven also ... and was assigned to the same office as Yang. Yang, who demonstrated on a number of occasions his generosity to physicists beginning their careers, told me about his idea of generalizing gauge invariance and we discussed it at some length ... I was able to contribute something to the discussions, especially with regard to the quantization procedures, and to a small degree in working out the formalism; however, the key ideas were Yang's.

The Scientist called Yang–Mills theory:<ref>Template:Cite web</ref>

The foundation for the current understanding of how subatomic particles interact is a contribution which has restructured modern physics and mathematics.

In 1956, he and T. D. Lee analyzed a problem known as the τ–θ puzzle, in which a particle called θ decayed into two pions and a particle τ into three pions, the two decays with different parity symmetry.<ref name=":8" /> However the two particles were not distinguishable.<ref name=":8" /> Lee and Yang proposed that, in the weak interaction, parity symmetry was not conserved and that it was the same particle (now known as the kaon K⁺).<ref name=":8" /> To test if weak interaction conserved parity, Lee contacted Chien-Shiung Wu's team at the National Bureau of Standards in Washington. Wu experiment experimentally verified the theory and the results were announced early in a press conference.<ref name=":8">Template:Cite web</ref> The results were also confirmed by two other independent experiments by Valentine Telegdi and Jerome Isaac Friedman at the University of Chicago and by Richard Garwin and Leon M. Lederman at Columbia University.<ref name=":8" /> All three experiments published their results in early 1957.<ref name=":8" /> That year, Yang and Lee received the 1957 Nobel Prize in Physics for this parity violation theory, which brought revolutionary change to the field of particle physics.<ref name="np" />

In the 1970s, Yang worked on the topological properties of gauge theory, collaborating with Tai Tsun Wu to elucidate the Wu–Yang monopole, a type of magnetic monopole. Unlike the Dirac monopole, it has no singular Dirac string.<ref>Template:Cite book</ref> Their 1975 paper, known as the Wu–Yang dictionary, helped bridge gaps between physics and differential geometry.<ref>Template:Cite web</ref><ref>Template:Cite book</ref>

On Yang's retirement from SUNY in 1999, Freeman Dyson called Yang "the pre-eminent stylist" of 20th-century physics alongside Albert Einstein and Paul Dirac, citing how Yang "turns his least important calculations into miniature works of art, and turns his deeper speculations into masterpieces."<ref name="nytimes obit" /> In 2009, Dyson wrote:<ref name=":4" />

13 seminal contributions

In 2012, there were celebrations for Yang's 90th birthday. The Chinese University of Hong Kong hosted a scientific conference and dinner banquet to announce the creation of the CN Yang archive.<ref>Template:Cite web</ref><ref name=":5">Template:Cite web</ref> Physicist Kenneth Young opened the ceremony.<ref name=":5" /> Yang also received a black cube from Tsinghua University<ref name=":6">Template:Cite book</ref> with 13 of his seminal contributions engraved on the faces of the cube. On the cube is also written "Congratulations on Professor Chen Ning Yang's 90th birthday" in Chinese. The cube also includes an ancient Chinese poem used by Yang in his 2013 Selected Papers and Commentaries; it reads:<ref name=":4" />

The 13 contributions engraved on the cube are:<ref name=":4">Template:Cite journal</ref>

• Statistical mechanics:
  • Phase transitions (1952): for his works with Lee on the Lee–Yang theory and the Lee–Yang theorem, which describe the liquid-gas phase transition based on microscopic properties.<ref name=":3">Template:Cite book</ref><ref name=":4" />
  • Bosons (1957): for Lee–Huang–Yang correction for a weakly interacting Bose gas, in collaboration with Lee and Kerson Huang. It explains the stability of Bose–Einstein condensates and superfluids.<ref>Template:Cite book</ref><ref name=":4" /><ref name=":6" />
  • Yang–Baxter equation (1967): consistent condition for a one-dimensional factorized scattering many-body system, which resurrected the interest in the Bethe ansatz and allowed to better description of 1D fermions.<ref>Template:Cite book</ref><ref name=":4" />
  • Finite temperature (1969): for the Yang–Yang thermodynamics formalism for 1D bosons, in collaboration with his brother Chen-Ping Yang (1930–2018<ref>Template:Cite web</ref>).<ref>Template:Cite web</ref><ref name=":4" /> The predictions of this formalism where demonstrated in 2008 using ultracold atoms.<ref name=":6" />
• Condensed matter physics:
  • Flux quantization (1961): for Byers–Yang theorem in superconductors, in collaboration with Nina Byers. They showed that the magnetic flux trapped in a superconducting ring is given by half of the usual magnetic flux quantum.<ref name=":4" /><ref>Template:Cite journal</ref>
  • OLDRO (1962): for his development of the concept of off-diagonal long-range order (OLDRO) that characterizes macroscopic quantum phenomena like superconductivity and superfluidity.<ref>Template:Cite journal</ref><ref name=":4" />
• Particle physics:
  • Parity non-conservation (1956): for predicting the violation of parity symmetry with Lee, for which they were awarded the Nobel Prize in Physics in 1957.<ref name=":4" />
  • T, C, and P (1957): work on explaining the relation between parity (P), charge (C) and time-reversal (T) symmetries, now known as CPT symmetry. Done in collaboration with Lee and Reinhard Oehme.<ref>Template:Cite journal</ref>
  • Neutrino experiment (1960): for the Lee and Yang paper that proposed to study the weak interaction with high energy neutrinos. This work promoted various neutrino experiments.<ref name=":4" /><ref>Template:Cite journal</ref>
  • CP nonconservation (1964): for his paper on CP violation, in collaboration with T. T. Wu.<ref>Template:Cite journal</ref><ref name=":4" />
• Field theory:
  • Gauge theory (1954): for Yang–Mills theory, in collaboration with Robert Mills.<ref name=":4" />
  • Integral formalism (1974): for giving meaning to the nonintegral phase factor in gauge theories.<ref name=":4" />
  • Fiber bundle (1975): for the Wu–Yang dictionary, in collaboration with T. T. Wu.<ref name=":4" />

Awards and honors

Yang was elected a Fellow of the American Physical Society in 1955,<ref>Template:Cite web</ref> the first foreign-to-domestic member of the Chinese Academy of Sciences,<ref>Template:Cite news</ref> the Academia Sinica in 1958,<ref>Template:Cite web</ref> the Russian Academy of Sciences,<ref>Template:Cite web</ref> and the Royal Society.<ref>Template:Cite web</ref> He was an elected member of the American Academy of Arts and Sciences,<ref>Template:Cite web</ref> the American Philosophical Society,<ref>Template:Cite web</ref> and the United States National Academy of Sciences.<ref>Template:Cite web</ref> He was awarde Princeton University (1958),<ref>Template:Cite web</ref> Moscow State University (1992),<ref>Template:Cite web</ref> and the Chinese University of Hong Kong (1997).<ref name=":2">Template:Cite web</ref>

List of awards

• Ten Outstanding Young Americans (1957)<ref>Template:Cite web</ref>
• Nobel Prize in Physics (1957) with T. D. Lee.
• Rumford Prize (1980), with Robert Mills.<ref>Template:Cite web</ref>
• National Medal of Science (1986)<ref>Template:Cite web</ref>
• First laureate of the Oskar Klein Memorial Lecture and Medal (1988)<ref>Template:Cite web</ref>
• Benjamin Franklin Medal for Distinguished Achievement in the Sciences of the American Philosophical Society (1993)<ref name="franklinscience_recipients">Template:Cite web</ref>
• Bower Award (1994)<ref>Template:Cite web</ref>
• Albert Einstein Medal (1995)<ref>Template:Cite web</ref>
• Lars Onsager Prize (1999)<ref>Template:Cite web</ref>
• King Faisal International Prize (2001)<ref>Template:Cite web</ref>
• Marcel Grossmann Awards (2015), "for deepening Einstein's geometrical approach to physics in the best tradition of Paul Dirac and Hermann Weyl"<ref>MG14, Marcel Grossmann Awards, Rome 2015 ICRANet and ICRA Template:Webarchive. Retrieved 28 April 2024.</ref>
• Asian Scientist 100, Asian Scientist (2016 and 2020)<ref>Template:Cite web</ref>

Awards and places named after him

Yang was the first president of the Association of Asia Pacific Physical Societies (AAPPS) when it was established in 1989.<ref>Template:Cite web</ref> In 1997, the AAPPS created the C. N. Yang Award in his honor to highlight young researchers.<ref>Template:Cite web</ref>

In 1998, after his retirement, the Institute of Theoretical Physics of Stony Brook University was renamed C. N. Yang Institute for Theoretical Physics.<ref>Template:Citation</ref> The C. N. Yang Hall, a residence hall and activity center at Stony Brook University, was dedicated in 2010.<ref>Template:Cite news</ref>

Selected publications

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See also

• List of Chinese Nobel laureates
• List of theoretical physicists

References

Sources

• Lee, T. D. and Yang, C. N. "Elementary Particles and Weak Interactions Template:Webarchive", Brookhaven National Laboratory (BNL), United States Department of Energy (through predecessor agency the Atomic Energy Commission), (1957).
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• Yang, C. N. "The Many Body Problem. Physics Monographs No. 6 Template:Webarchive," Rio de Janeiro. Centro Brasileiro de Pesquisas Fisicas, 1960.
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• Yang, C. N. "Mathematical Deductions from Some Rules Concerning High-Energy Total Cross Sections Template:Webarchive," Brookhaven National Laboratory (BNL), United States Department of Energy (through predecessor agency the Atomic Energy Commission), (1962).
• Yang, C. N. "Symmetry Principles In Physics. Brookhaven Lecture Series Number 50 Template:Webarchive," Brookhaven National Laboratory (BNL), United States Department of Energy (through predecessor agency the Atomic Energy Commission), 13 October 1965.
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External links

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• Interview of Chen Ning Yang by John Israel and Larry Schneider on 1980 November 1, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA
• Professor Chen Ning Yang (homepage – Institute for Advanced Study, Tsinghua University)
• Chen Ning Yang (homepage – Stony Brook University)
• Template:Nobelprize including the Nobel Lecture, 11 December 1957 The Law of Parity Conservation and Other Symmetry Laws of Physics
• The Shaw Prize, Structure Template:Webarchive (homepage – Shaw Prize)
• Symmetries and Reflections (C.N. Yang retirement symposium at Stony Brook University)
• The CN Yang Scholars Programme Template:Webarchive at Nanyang Technological University Template:Webarchive, Singapore
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