Robert Osserman, professor emeritus of mathematics, died Nov. 30 at his home in Berkeley. He was 84.

He joined the Stanford faculty in 1955 and served as chair of the Department of Mathematics from 1973 to 1979. He was the Andrew W. Mellon Professor of Interdisciplinary Studies from 1987 to 1990.

From 1990 to 1995, he served as the deputy director of the Mathematical Sciences Research Institute in Berkeley, an organization that he helped to found in the early 1980s. He helped it become one of the world’s premier research centers for mathematics and served as its director of special projects until his death.

During his long career, Osserman held visiting appointments at the University of Colorado, the Courant Institute, Harvard and the University of California-Berkeley, and was also the recipient of Fulbright and Guggenheim fellowships. In 1960-61, he was head of the Mathematics Branch of the Office of Naval Research in Washington, D.C.

Osserman received his PhD from Harvard University, where he wrote his thesis under the direction of Lars Ahlfors. He initially worked in the field of Riemann surfaces and complex analysis. Early in his career, he became aware of minimal surfaces – mathematical generalizations of soap films – that minimize area among all surfaces with the same boundary.

As far back as the 18

^{th}century, mathematicians studying minimal surfaces wrestled with questions that were easy to state but stubbornly difficult to solve, until Osserman and Ahlfors made important breakthroughs.

**Mathematical study of minimal surfaces**

Osserman was able to exploit the classical connection between formulas that represent these surfaces and complex analysis. He created far-reaching extensions of this relationship, and then used these insights to resolve many open questions in the field. His monograph

*Survey of Minimal Surfaces*, first published in 1969, with a second edition in 1986, remains a standard reference in the subject and has introduced this beautiful subject to generations of mathematicians.

Minimal surfaces and their generalizations are central to geometric analysis, an area of research that has connections to many areas in physics, the calculus of variations, Riemannian geometry and partial differential equations. During his tenure as chair of Stanford’s math department and for the decade that followed, Osserman played a key role in hiring and nurturing many of the world’s best mathematicians in this area, helping the university to become a world leader in this very important field of mathematics.

Osserman authored or co-authored more than 70 research papers. He was the thesis supervisor for nine graduate students, many of whom have gone on to be successful researchers and professors in geometry, topology and computer science.

"Bob Osserman was my thesis adviser, my colleague and my very dear friend," said Blaine Lawson, who was his first PhD student and is now a professor of mathematics at Stony Brook University and a member of the National Academy of Sciences. "He was a mentor of tremendous influence in my mathematical development and on my outlook on mathematical life. He was a man of immense erudition and personal warmth and charm."