Lars Edvard Phragmén
His work focused on elliptic functions and complex analysis. His most famous result is the extension of Liouville's theorem to analytic functions on a sector. A first version was proposed by Phragmén, then improved by the Finnish topologist Ernst Lindelöf. They jointly published this last version, known as the Phragmén–Lindelöf principle.
He left the university in 1903, joining the Royal Inspection of Insurance Companies. He became director the following year. In 1908, he was appointed director of the insurance company Allmänna Lifförsakringsbolaget.
From 1889 until his death, he was an active editor of Acta Mathematica. He is also famous for having pointed out (at 26) an unclear part of Henri Poincaré's preprint on the three body problem. This led Poincaré to discover a major mistake in his own work, paving the way to important developments in chaos theory.
In addition to analysis, Phragmén was interested in the mathematics underlying insurance companies, and voting.
- « Sur une extension d'un principe classique de l'analyse et sur quelques propriétés des fonctions monogènes dans le voisinage d'un point singulier », Acta Math. 31, 1908
- Yngve Domar, « Mathematical research during the first decades of the University of Stockholm », Stockholm University, 1978 (written and translated by H. Troy and H.S. Shapiro)