Shiing-Shen Chern

Shiing-Shen Chern (, ; October 28, 1911 – December 3, 2004) was a Chinese American mathematician and poet.

He made fundamental contributions to differential geometry and topology.

He has been called the "father of modern differential geometry" and is widely regarded as a leader in geometry and one of the greatest mathematicians of the twentieth century, winning numerous awards and recognition including the Wolf Prize and the inaugural Shaw Prize.

Chern was born in Xiushui, Jiaxing, China in 1911.

He graduated from Xiushui Middle School and subsequently moved to Tianjin in 1922 to accompany his father.

In 1926, after spending four years in Tianjin, Chern graduated from Fulun High School.

At age 15, Chern entered the Faculty of Sciences of the Nankai University in Tianjin and was interested in physics, but not so much the laboratory, so he studied mathematics instead.

Chern graduated with a Bachelor of Science degree in 1930.

At Nankai, Chern's mentor was mathematician Jiang Lifu, and Chern was also heavily influenced by Chinese physicist Rao Yutai, considered to be one of the founding fathers of modern Chinese informatics.

Chern went to Beijing to work at the Tsinghua University Department of Mathematics as a teaching assistant.

At the same time he also registered at Tsinghua Graduate School as a student.

He studied projective differential geometry under Sun Guangyuan, a University of Chicago-trained geometer and logician who was also from Zhejiang.

Sun is another mentor of Chern who is considered a founder of modern Chinese mathematics.

In 1932, Chern published his first research article in the Tsinghua University Journal.

In 1932, Wilhelm Blaschke from the University of Hamburg visited Tsinghua and was impressed by Chern and his research.

In the summer of 1934, Chern graduated from Tsinghua with a master's degree, the first ever master's degree in mathematics issued in China.

Yang Chen-Ning's father, Yang Ko-Chuen, another Chicago-trained professor at Tsinghua, but specializing in algebra, also taught Chern.

At the same time, Chern was Chen-Ning Yang's teacher of undergraduate maths at Tsinghua.

At Tsinghua, Hua Luogeng, also a mathematician, was Chern's colleague and roommate.

In 1934, Chern received a scholarship to study in the United States at Princeton and Harvard, but at the time he wanted to study geometry and Europe was the center for the maths and sciences.

He studied with the well-known Austrian geometer Wilhelm Blaschke.

Co-funded by Tsinghua and the Chinese Foundation of Culture and Education, Chern went to continue his study in mathematics in Germany with a scholarship.

Chern studied at the University of Hamburg and worked under Blaschke's guidance first on the geometry of webs then on the Cartan-Kähler theory and invariant theory.

He would often eat lunch and chat in German with fellow colleague Erich Kähler.

He had a three-year scholarship but finished his degree very quickly in two years.

He obtained his Dr. rer.nat. (Doctor of Science, which is equivalent to PhD) degree in February, 1936.

He wrote his thesis in German, and it was titled Eine Invariantentheorie der Dreigewebe aus r-dimensionalen Mannigfaltigkeiten im R_{2r} (English: An invariant theory of 3-webs of r-dimensional manifolds in R_{2r}).

For his third year, Blaschke recommended Chern to study at the University of Paris.

It was at this time that he had to choose between the career of algebra in Germany under Emil Artin and the career of geometry in France under Élie-Joseph Cartan.

Chern was tempted by what he called the "organizational beauty" of Artin's algebra, but in the end, he decided to go to France in September 1936.

He spent one year at the Sorbonne in Paris.

There he met Cartan once a fortnight.

Chern said: "Usually the day after [meeting with Cartan] I would get a letter from him. He would say, “After you left, I thought more about your questions...”—he had some results, and some more questions, and so on. He knew all these papers on simple Lie groups, Lie algebras, all by heart. When you saw him on the street, when a certain issue would come up, he would pull out some old envelope and write something and give you the answer. And sometimes it took me hours or even days to get the same answer... I had to work very hard."In August 1936, Chern watched the Summer Olympics in Berlin together with Chinese mathematician Hua Luogeng who paid Chern a brief visit.

Chern worked at the Institute for Advanced Study (1943–45), spent about a decade at the University of Chicago (1949-1960), and then moved to University of California, Berkeley, where he cofounded the Mathematical Sciences Research Institute in 1982 and was the institute's founding director.

Renowned coauthors with Chern include Jim Simons, an American mathematician and billionaire hedge fund manager.

Chern's work, most notably the Chern-Gauss-Bonnet Theorem, Chern–Simons theory, and Chern classes, are still highly influential in current research in mathematics, including geometry, topology, and knot theory; as well as many branches of physics, including string theory, condensed matter physics, general relativity, and quantum field theory.

Chern's surname (陳) is a common Chinese surname which is conventionally romanized as Chan or Chen.

The spelling "Chern" is from Gwoyeu Romatzyh (GR) romanization’s tonal spelling.

In English, Chern pronounced his own name as "Churn".

In memory of Shiing-Shen Chern, the International Mathematical Union established the Chern Medal in 2010 to recognize "an individual whose accomplishments warrant the highest level of recognition for outstanding achievements in the field of mathematics".