Obituary: Alberto CalderonUniversity Professor Emeritus in Mathematics Alberto Calderon (Ph.D.'50), widely regarded as one of the most influential mathematicians of the 20th century, died April 16 at Northwestern Memorial Hospital after a brief illness. He was 77.Calderon, University Professor Emeritus in Mathematics, is best known for his contributions to mathematical analysis, the large branch of mathematics that includes calculus, infinite series and the analysis of functions. Together with his mentor, Antoni Zygmund, he founded the "Chicago school of analysis," the most influential school in that branch of mathematics in the 20th century. "He was one of the most original and profound mathematical analysts of the past 50 years," said Felix Browder, the Max Mason Distinguished Service Professor Emeritus in Mathematics and former vicepresident of Rutgers University. "Calderon was one of the central links between two major areas of mathematical analysis, namely Fourier analysis and partial differential equations. He made outstanding contributions to both fields and laid much of the groundwork for other people's work in these areas." Browder added, "Calderon was also a man of really remarkable upright character. He was universally respected and admired because of his extreme probity and generosity." Calderon's many honors include the 1991 National Medal of Science; the 1989 Wolf Prize; the 1989 Steele Prize from the American Mathematical Society; Argentina's Consagracion Nacional Prize, awarded in 1989; and the 1979 Bocher Memorial Prize from the American Mathematical Society. In pioneering work with his mentor, Calderon formulated a theory, now known as the CalderonZygmund theory, of what are called singular integrals. "These singular integrals have tremendous applications within pure mathematics, as well as very important applications in industrial problems," said Robert Fefferman, Louis Block Professor and Chairman of Mathematics. "It is unquestionably one of the most important developments in analysis in the 20th century." Singular integrals are mathematical objects that look infinite, but when interpreted properly are finite and wellbehaved. Calderon later showed how these singular integrals could be used to obtain estimates of solutions to equations in geometry and to analyze functions of complex variables. He also showed how singular integrals could provide entirely new ways to study partial differential equations, which are widely used to solve problems in physics and engineering. After receiving his Ph.D. from Chicago, Calderon served as a visiting associate professor at Ohio State University, a visiting member of the Institute for Advanced Study and then as associate professor at M.I.T. He returned to Chicago as Professor in Mathematics in 1959, and aside from brief periods in which he returned to M.I.T. and to Argentina, his birthplace, has been at Chicago ever since. He also had been an honorary professor at the University of Buenos Aires since 1975. Calderon was a member of the National Academy of Sciences and the American Academy of Arts and Sciences, as well as numerous other such academies around the world. He is survived by his wife, noted mathematician Alexandra Bellow, recently retired from Northwestern University, whom he married in 1989; and two children from his first marriage, Mary Josephine, of St. Charles, Ill., and Pablo, of New York, N.Y. His first wife, Mabel, to whom he was married for 35 years, died in 1985.
