Augustin-Louis Cauchy
Augustin-Louis Cauchy (Paris, August 21 1789 – Sceaux, May 23, 1857) was one of the most prominent mathematicians of the first half of the 19th century. He was the first to give a rigorous basis to the concept of limits. He established a convergence criterion for sequences of the type that are now called Cauchy sequences. The Cauchy condition for the convergence of series can be found in any present-day textbook on calculus. Probably Cauchy is most famous for his singlehanded development of complex function theory, with Cauchy's residue theorem as the fundamental result.
Cauchy was a prolific writer, he wrote more than 800 research articles and five complete textbooks. He was a devout Roman Catholic, strict (Bourbon) royalist, and a close associate of the Jesuit order.
Biography
Cauchy's father (Louis-François Cauchy) was a high official in the Parisian Police of the Old Régime. He lost his position because of the French Revolution (July 14, 1789) that broke out one month before Augustin-Louis was born. This fact is sometimes seen as the cause of the deep hatred of the French Revolution that Cauchy felt all through his life. The Cauchy family survived the revolution and the following Reign of Terror (1794) by escaping to Arcueil, where Cauchy jr. got his first education from his father. After the death of Robespierre (1794) it was safe for the family to return to Paris, where Cauchy sr. found himself a new bureaucratic job and where he quickly moved up the ranks. When Napoleon Bonaparte came to power (1799) Cauchy sr. made further promotion to Secretary-General of the Senate working directly under Laplace, who is now better known for his work on mathematical physics. Also the famous mathematician Lagrange was no stranger to the Cauchy family.
On Lagrange's advice Augustin-Louis was enrolled in the École Central du Panthéon in the fall of 1802. This was the best secondary school of Paris at that time. Most of the curriculum consisted of classical languages and the young ambitious Cauchy, being a brilliant student, won many prizes in Latin and Humanities. In spite of these successes, Augustin-Louis decided for an engineering career and prepared himself for the entrance examination to the École Polytechnique. In 1805 he became second out of 293 applicants on this examination, and was, of course, admitted. This school gave future civil and military engineers a high-level scientific and mathematical education, but functioned under military discipline, which caused the young pious Cauchy some problems in adapting. Nevertheless, he finished the Polytechnique in 1807 at the age of 18 and went on to the École des Ponts et Chaussées (School for Bridges and Highways). He graduated as a civil engineer in 1810 with the highest honors and accepted a job as junior engineer in Cherbourg, where Napoleon intended to build a naval port.
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Reference
Bruno Belhoste, Augustin-Louis Cauchy: a biography, translated from the French by F. Ragland, Springer, New York (1991). ISBN 0-387-97220-X