Alberto Calderón (käldārōn´), 1920–98, Argentine mathematician, b. Mendoza, Argentina, grad. Univ. of Buenos Aires (B.S. 1947), Univ. of Chicago (Ph.D. 1950). He is known for his contributions to mathematical analysis and the development of singular integrals, which are crucial to pure mathematics and to the mathematical description of physical functions, such as heat conduction and sound transmission. With his mentor Antoni Zygmund he formulated the Calderón-Zygmund theory of singular integral operators and inspired the Calderón-Zygmund, or Chicago, school of mathematicians devoted to their study. In particular Calderón wanted to describe a calculus for elliptic differential operators; from this beginning in the 1950s, the theory of pseudodifferential operators grew in the 1960s. Calderón's influence on analysis and related areas is due in large part to the many methods that he invented and perfected. Calderón's techniques have been absorbed as standard tools not only of harmonic analysis and but also of nonlinear analysis, partial differential equations, complex analysis, and even signal processing and numerical analysis.