A native of France, Gerard Debreu spent most of his professional life at the University of California at Berkeley. He started as a professor of economics in 1962 and was appointed professor of mathematics in 1975. Before his almost 30-year tenure at UC Berkeley, Debreu worked from 1950 to 1960 at the University of Chicago and Yale University for the Cowles Commission for Research in Economics, and at Stanford 's Center for Advanced Study in the Behavioral Sciences from 1960 to 1961.

In a famous paper coauthored with Kenneth Arrow and published in 1954, Debreu proved that prices exist that bring markets into equilibrium. In his 1959 book, The Theory of Value, Debreu introduced more general equilibrium theory, using complex analytic tools from mathematics—set theory and topology—to prove his theorems.  In 1983 he was awarded the Nobel Prize “for having incorporated new analytical methods into economic theory and for his rigorous reformulation of the theory of general equilibrium.”

Gerard Debreu was an important contributor to the development of formal mathematical models within economics. He brought to economics a mathematical rigor that had not been seen before. This mathematical rigor made lasting changes to the field of economics, making it a more formal science, especially in the field of general equilibrium modeling.

http://www.nobelprize.org/nobel_prizes/economics/laureates/1983/debreu.html

http://www.berkeley.edu/news/media/releases/2005/01/05_debreu.shtml