Zassenhaus, Hans Julius (1912–1991)

German mathematician who mainly studied group theory and number theory. Zassenhaus groups form part of the basis for the contemporary development of finite group theory.

Zassenhaus was born in Koblenz and studied at Hamburg. He was professor at Montréal, Canada, 1949–59. Transferring to the USA, he finally became professor at Ohio State in 1964.

Group theory is the study of systems in which the product of any two members of a system results in another member of the same system (for example, even numbers). Zassenhaus's most significant results were obtained in his investigations into finite groups. In group extensions he postulated with Issai Schur (1875–1941) what has become known as the Schur–Zassenhaus theory.

Zassenhaus also made contributions to the study of Lie algebras, the geometry of numbers, and applied mathematics.