Chen Ning Yang, a Nobel Prize-winning theoretical physicist whose feel for mathematical aesthetics helped reveal a surprising kink in the weave of nature, died on Saturday in Beijing. He was 103.
His death was announced by Tsinghua University in Beijing, where Dr. Yang taught for many years.
他去世的消息由位于北京的清华大学宣布，杨振宁博士曾在该校任教多年。
Dr. Yang and a colleague, the physicist Tsung-Dao Lee, created a sensation in 1956 by proposing that one of the four forces of nature might violate a seemingly ironclad principle called conservation of parity — a way of saying that a phenomenon and its mirror image should behave precisely the same. Their prediction was quickly borne out by experiment, and they shared the Nobel Prize in Physics.
When Dr. Yang retired from the State University of New York at Stony Brook (now Stony Brook University) in 1999, a colleague, the distinguished physicist Freeman Dyson, called him “the pre-eminent stylist” of 20th-century physics, exceeded only by Albert Einstein and Paul Dirac.
Dr. Yang’s sense of mathematical beauty, Dr. Dyson said, “turns his least important calculations into miniature works of art, and turns his deeper speculations into masterpieces.”
In later years Dr. Yang became well known in China, where he helped lead the effort to promote basic research. His fame only increased when in 2004, at age 82, he married Weng Fan, a 28-year-old graduate student at the Guangdong University of Foreign Studies, whom he had met in 1995 when she served as an interpreter at an international physics seminar. She was, he was quoted as saying in the newspaper The China Daily, his “final blessing from God.”
Dr. Yang — he called himself Frank, after Benjamin Franklin — was part of a generation of young theorists who, after World War II, were confronted with strange new particles bombarding the earth as cosmic rays, begging for explanation. In 1956, he and Dr. Lee took on one of the strangest: a particle, now called the K meson or kaon, that was first revealed by the tracks it left in detectors lofted in balloons and placed on mountaintops.
Sometimes a kaon broke into two smaller pieces, called pions, and sometimes it broke into three. That in itself was not so bad, but they decayed in a way that appeared to violate parity conservation, the mirror symmetry long thought to pervade the physical world.
Rather than accept that the principle didn’t apply to these nuclear decays, physicists were forced to posit the existence of two kinds of kaons, christened the theta and the tau. Identical in other respects, they disintegrated in different ways.
Like many theorists, Dr. Yang and Dr. Lee wondered whether the explanation was merely a contrivance — an ad hoc way to get around an awkward experimental result. On a spring day in 1956, Dr. Yang — who was based at the Institute for Advanced Study in Princeton, N.J., and spending time at the Brookhaven National Laboratory on Long Island — came to New York City for a regular visit with Dr. Lee, who was at Columbia University.
At lunch at a nearby Chinese restaurant, the two scientists confronted the possibility that the weak force — the engine of nuclear disintegration — ignored mirror symmetry. In a landmark paper published that fall in The Physical Review, they suggested how to find out.
The Columbia physicist Chien-Shiung Wu took on the challenge and showed in an experiment at the National Bureau of Standards (now the National Institute of Standards and Technology) in Washington that parity was indeed violated by the weak force. As they decayed, atomic nuclei emitted more electrons in one direction than in the other. The symmetry didn’t hold.
The slow gears of Stockholm shifted into high, and in 1957 the two physicists were awarded perhaps the quickest Nobel Prize ever. They were the first Chinese-born laureates. People began to speak of “Lee and Yang” or “Yang and Lee” as if they were a single person, unaware that their relationship was already becoming frayed.
Chen Ning Yang was born on Oct. 1, 1922 (although some published sources give the date as Sept. 22), in Hefei, China, about 300 miles west of Shanghai, the eldest of five children of Yang Wu-zhi and Luo Meng-hua. His father was a professor of mathematics.
Dr. Yang’s family lived in Beijing during much of his childhood and early teens, but with the outbreak of war with Japan the family fled to Kunming, in the south. In 1940, the courtyard of the family home was bombed as part of the Japanese effort to shut down the Burma Road, the British supply line to the Chinese nationalists, which terminated in Kunming. After the bombing, the family moved to a suburb.
Shortly after earning a master’s degree in 1944 from Tsinghua University, which during the war had been relocated to Kunming from Beijing, Dr. Yang went to the United States on a fellowship, hoping to study at Columbia with Enrico Fermi, the Italian-born physicist who had overseen the first successful nuclear chain reaction.
Surprised to find that Dr. Fermi was headed for the University of Chicago to work on the Manhattan Project, which developed the atomic bomb, Dr. Yang followed him there. It was Dr. Fermi, he later wrote, who taught him that abstractions must be tethered to experiment, that “physics is to be built from the ground up, brick by brick, layer by layer.”
At Chicago, Dr. Yang met up with Dr. Lee, an acquaintance from his student days in China. Completing his thesis under Edward Teller, the Hungarian-born architect of the hydrogen bomb, Dr. Yang received his doctorate in 1948 and, after teaching for a year at Chicago, moved to the Institute for Advanced Study to work for Robert Oppenheimer, who was then its director.
Dr. Yang would recall one encounter he had with the institute’s most famous faculty member, Dr. Einstein. Dr. Yang had just published a paper in the The Physical Review, and Dr. Einstein wanted to discuss it with him. They spoke for an hour and a half, Dr. Yang said, but he “did not get very much out of that conversation.”
“He spoke very softly,” he said, “and I found it difficult to concentrate on his words, being quite overwhelmed by the nearness of a great physicist whom I had admired for so long.”
Once established in Princeton, Dr. Yang began spending his summers at Brookhaven, where he and an officemate, Robert L. Mills, collaborated on what became known as the Yang-Mills theory, the scaffolding on which much of modern particle physics has been built. Using an idea called gauge theory that had been developed by the German mathematician Herman Wyl, they created the gauge principle, which explains the interactions and, importantly, the self-interactions, of electromagnetic, weak and strong forces at the heart of quantum physics.
“At the time that we wrote it down,” Dr. Yang said of the theory in a 2006 interview at Stony Brook, “nobody believed that it was important and we didn’t know that it was that important, but we said that this is a beautiful idea and the mathematical structure is very elegant, so we published that paper about it. And then 20 years later, various experiments showed that that was approximately the right direction. Then after struggling for another five years, it became clear that it is not just approximately right, it is exactly right.”
He was also collaborating with Dr. Lee, who moved to Columbia after a stint at the Institute for Advanced Study. Beginning in 1956, they published 32 papers together.
But tensions were emerging in the partnership, and the two parted ways in 1962. To Dr. Lee’s consternation, Dr. Yang would sometimes pull rank, insisting that his name come first because he was four years older. For this and other reasons, Dr. Lee wrote in a remembrance in 1986, “The delicate symmetry between Yang and myself was disturbed.”
Long after, in an interview published in Newsday in 2000, Dr. Yang called the split “a tragedy.”
多年以后，杨振宁2000年在《新闻日报》刊登的一次采访中称这次分裂为“一场悲剧”。
Dr. Yang was not always modest about his accomplishments. As he approached his 60th birthday, some admiring colleagues offered to contribute papers to a celebratory volume, known as a Festschrift, honoring his legacy. Dr. Yang concluded that a collection of his own papers with commentaries would be more interesting.
In that anthology, he described the origins of the Nobel-winning work on parity, giving himself most of the credit. Dr. Lee later published a very different account.
Dr. Yang left the Institute for Advanced Study in 1966 to become Stony Brook’s Albert Einstein professor of physics and the director of what is now the C.N. Yang Institute for Theoretical Physics.
杨振宁于2009年在香港出席邵逸夫奖的颁奖典礼并发表讲话。 Mike Clarke/Agence France-Presse — Getty Images
After a visit to China in 1971, Dr. Yang began reforging old ties. He would later serve as director of the Institute of Mathematical Sciences at the Chinese University of Hong Kong and as a professor at his alma mater, Tsinghua University. In 2015, he gave up his United States citizenship to become a citizen of China.
Dr. Yang’s wife of 53 years, Chih Li Tu, whom he had met in China when he was teaching middle school and she was a student, died in 2003. In addition to his second wife, Weng Fan, his survivors include three children from his first marriage, Franklin, Gilbert and Eulee Yang; and two grandchildren.
In the interview with Newsday, Dr. Yang said he doubted that physicists would ever converge on a theory of everything.
在接受《新闻日报》采访时，杨振宁表示，他怀疑物理学家们是否有朝一日能够对“万有理论”达成共识。
“Nature is extremely subtle,” he said. “I happen to think that the depth of natural substances cannot be fathomed by mankind. Because after all we only have, let’s say, 100 billion neurons. How can you match that with the infinite depth of nature?”
杨振宁（左），1957年他与李政道（中）共同获得诺贝尔物理学奖。获奖后，人们开始将他们合称为“李杨”或“杨李”，仿佛他们是同一个人。