December 7, 2004
Shiing-Shen Chern, 93, Innovator in New Geometry, Is Dead
By KENNETH CHANG
r. Shiing-Shen Chern, a mathematician whose seemingly purely abstract discoveries about the twistings of geometric surfaces have found wide use in physics and mathematics, died Friday at his home in Tianjin, China. He was 93.
Dr. Chern also helped set up three mathematics institutes, two in China and one at the University of California, Berkeley. Nankai University, where Dr. Chern established an institute in 1985, reported his death.
"He's a towering figure in 20th-century mathematics," said Dr. Calvin C. Moore, a professor of mathematics at the University of California, Berkeley.
Dr. Chern's work in a field called differential geometry looked at the way the curvature of a surface can tell something about the overall shape. For example, someone standing on a sphere will see the surface dropping off in all directions. But on other shapes, like that of a doughnut, there must be places - around the hole, in particular - where the surface is shaped like a saddle, curving upward in some directions.
The field was pioneered in the 19th century by Carl Friedrich Gauss, who wanted to know how to accurately survey the landscape of a curved planet, but interest had waned by the 1930's, Studying the curvature of surfaces in spaces greater than three dimensions, Dr. Chern devised mathematical quantities, which he called characteristic classes, that differentiated different types of surfaces. "Everyone else in the world called them Chern classes," Dr. Moore said.
For example, a strip of paper whose ends are glued together as a ring is in a different Chern class than one that has been twisted into a Möbius strip. "Chern classes measure the degree of twisting in different dimensions," said Dr. Jeff Cheeger, a professor of mathematics at New York University.
Chern classes and later advances in differential geometry have now found applications in fields as diverse as string theory in theoretical physics and computer graphics. "I think that he, more than anyone, was the founder of one of the central areas of modern mathematics," said Dr. Phillip A. Griffiths, a professor at the Institute for Advanced Study in Princeton, N.J.
Born in 1911 in Jiaxing, China, Shiing-Shen Chern started college at Nankai University in Tianjin at 15. He finished his doctorate in just a year and a half at the University of Hamburg in Germany.
He accepted a professorship at Qinghua University in Beijing, but World War II disrupted those plans. After teaching for several years at temporary campuses, Dr. Chern fled China - a circuitous westward journey on a series of military flights, through India, Africa, Brazil, Central America and Miami - to pursue his research at the Institute for Advanced Study.
He returned to China after World War II and helped found a mathematics institute for Academia Sinica. The civil war in China led Dr. Chern to leave China again and return to the Institute for Advanced Study. He became a professor at the University of Chicago in 1949, then moved to Berkeley in 1960. He became an American citizen in 1961.
Dr. Chern retired in 1979, but two years later returned to full-time work when he founded Berkeley's Mathematical Sciences Research Institute with Dr. Moore and Dr. Isadore Singer, now at M.I.T. Dr. Chern was the director of the institute, which offers postdoctoral research positions, from 1981 to 1984.
"He took great pleasure in getting know and working with and helping to guide young mathematicians," Dr. Griffiths said. "I was one of them."
Dr. Chern received a United States National Medal of Science in 1975 and the Wolf Prize, one of the most prestigious honors in mathematics, in 1983. He was a member of the National Academy of Sciences.
In 1995, Robert G. Uomini, who had taken Dr. Chern's class on differential geometry as an undergraduate, won $22 million in a lottery and donated part of his winnings to establish a chair for his former professor.
Four years ago, after his wife of 61 years, Shih-ning Chern, died, Dr. Chern returned to China. He helped bring the International Congress of Mathematicians, a major conference, to Beijing in 2002.
Dr. Griffiths recalled a meeting that he and Dr. Chern attended with Jiang Zemin, then China's president, to persuade him to attend the congress's opening ceremony.
"It was clear Jiang Zemin revered this man," Dr. Griffiths said.
Dr. Chern is survived by a son, Paul, of Needham, Mass., and a daughter, May Chu, of Houston.
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