(1789–1857), French mathematician. Augustin-Louis Cauchy was born in Paris on Aug. 21, 1789. He founded the theories of elasticity, of functions of complex variables, and of substitution groups. He studied the concepts of limit and continuity in calculus and contributed to the theory of wave propagation and optics. From 1813 he held professorships in the Faculté des Sciences, the Collège de France, and the École Polytechnique, all in Paris. He went into exile in 1830 rather than swear allegiance to king Louis-Philippe. When the oath was suspended he returned to Paris in 1838 to resume his post at the École Polytechnique. (See also Mathematics.)