Georges Henri Halphen

Georges Henri Halphen was a French mathematician, born in Rouen in 1844 and raised in Paris, who worked on the singularity theory of algebraic curves, invariant theory and projective differential geometry. After studying at the Ecole Polytechnique and serving in the army during the Franco-Prussian war, he became a repetiteur there in 1872. His solution in 1873 of a problem of Chasles on families of conics brought him wide notice: he showed that Chasles was essentially correct but that restrictions on the kinds of singularity were needed, and he distinguished proper from improper solutions of an enumerative problem. He also classified singular points of algebraic curves, studied differential invariants in his 1878 doctoral dissertation, and made major contributions to linear differential equations and algebraic space curves. He won the Grand Prix of the Academie des Sciences in 1880 and the Steiner Prize in 1882, was elected to the Academie in 1886, and died in 1889 aged 44.