Lars Edvard Phragmén

Who was Lars Edvard Phragmén?

Lars Edvard Phragmén was a Swedish mathematician.

The son of a college professor, he studied at Uppsala then Stockholm, graduating from Uppsala in 1889. He became professor at Stockholm in 1892, after Sofia Kovalevskaia.

He left Uppsala less than a year after, becoming professor Mittag-Leffler's assistant at Stockholm. In 1884, he provided a new proof of the Cantor-Bendixson theorem.

His work focused on elliptic functions and complex analysis. His most famous result is the extension of Liouville's theorem to bounded entire functions. 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 an unclear part of Henri Poincaré's preprint on the three body problem.