Herbert B. Keller
1925 – 2008

Herbert B. Keller, professor of applied mathematics, emeritus, and a leader in numerical analysis and scientific computing, died in his Pasadena home on January 26, after his routine morning bicycle ride. He was 82.

The son of a bartender who loved numbers and puzzles, Keller was born in Paterson, New Jersey. He studied electronics at Georgia Tech and joined the Naval Reserve Officers Training Corps. During World War II, he became a fire-control officer in charge of the guns on the USS Mississippi, where he trained future president Jimmy Carter to be a gunnery officer.

Keller later went to New York University and received his PhD in mathematics in 1954. He eventually became a professor of applied mathematics at the Courant Institute of Mathematical Sciences at NYU. In 1965, he came to Caltech as a visiting professor and returned as a full professor two years later, joining the newly formed applied-mathematics group. He later became the executive officer for applied mathematics and director of Caltech’s branch of the Center for Research on Parallel Computation.

Keller made significant contributions toward techniques for solving complex problems with a computer. He was known for developing methods to solve two-point boundary-value problems, which arise in many areas of physics and engineering, from fluid flow to stellar structure. He also made strides in bifurcation theory, which looks at how changes in parameter values influence a system. One simple example is the problem of how changing the number of fishing licenses given out each year affects fish population dynamics. He remained an active researcher even after his retirement in 2000.

Colleagues described him as a mathematician with chutzpah, unafraid to speak his mind and to go after whatever problem interested him—advice that he doled out through the years as an influential mentor to dozens of students and postdocs. His fearless approach to research mirrored his other passion in life: cycling.

His brother recalled a cycling trip they took in the south of France in 1948, when they inadvertently joined the Tour de France after riding through roads lined with cheering spectators. Keller rediscovered the sport in the early 1980s, and despite suffering countless accidents—many with serious injuries—never stopped riding. In one of his most oft-told stories, he said a collision he had with a pile of lumber in Germany fixed his nearsightedness. Typically biking 100 to 150 miles a week, Keller didn’t allow age to slow him down—he finished a 1,250-mile European tour when he was 68. He completed several centuries and double centuries, which are rides stretching 100 or 200 miles; he said he rode his last double century when he was 72.

In addition to serving on numerous committees and councils, he was a fellow of the American Academy of Arts and Sciences, the American Association for the Advancement of Science, and the Guggenheim Foundation. He was the president of the Society of Industrial and Applied Mathematics, and later won their von Kármán Prize. With Eugene Isaacson, he coauthored a textbook that became a classic in numerical analysis.

His brother, Joseph, a retired professor of mathematics and mechanical engineering at Stanford University; his son, Steve; his daughter, Debra; and four grandchildren survive him. —MW