Augustin-Louis Cauchy: brilliant mathematician, stubborn royalist, dreadful tutor
More concepts and theorems carry Cauchy's name than any other mathematician's, sixteen in elasticity alone. Yet he spent five years in exile tutoring a teenage prince who hated maths and gleefully told everyone that his teacher had begun his career in the sewers of Paris.
Cauchy was born on 21 August 1789, a month after the storming of the Bastille cost his father a senior post in the Paris police. The family rode out the Terror in Arcueil, returned to Paris, and prospered under Napoleon, when his father became Secretary-General of the Senate under Laplace. Lagrange, a family friend, advised sending the boy to the École Centrale du Panthéon, where he collected prizes in Latin. In 1805 he placed second of 293 candidates for the École Polytechnique, then trained as a civil engineer and in 1810 went to Cherbourg to work on Napoleon's planned naval base.
Overwork and a growing love of pure mathematics brought him back to Paris in 1812. On largely unpaid sick leave he studied symmetric functions and higher algebraic equations and proved Fermat's polygonal number theorem. After Waterloo, the restored monarchy reorganized the Académie des Sciences in 1816, expelled Lazare Carnot and Gaspard Monge for political reasons, and installed Cauchy in one of the vacated seats. Colleagues were outraged, and he made lasting enemies. He became a full professor at the Polytechnique, where students found him a notoriously poor lecturer who crammed in far too much.
His output was immense: roughly eight hundred research articles and five complete textbooks. He was among the first to state and prove the core theorems of calculus rigorously, effectively founding real analysis, and he pioneered complex analysis, the theory of permutation groups and continuum mechanics. He married Aloïse de Bure, whose family of printers published most of his work, in 1818 at Saint-Sulpice, and they had two daughters.
Politics then derailed him. After the July Revolution of 1830 he refused to swear allegiance to Louis Philippe and lost every post except his academy seat. He held a chair of theoretical physics in Turin created for him by the King of Sardinia, then from 1833 tutored Henri d'Artois, grandson of the deposed Charles X, in Prague, producing almost no research. He was made a baron, a title he prized. Back in Paris in 1838 he was elected to the Bureau des Longitudes but, still refusing the oath, was never approved, and was replaced by Louis Poinsot at the end of 1843. He died on 23 May 1857.
Source: Augustin-Louis Cauchy
