Sigurður Helgason (mathematician)

Sigurður Helgason (born November 8, 1927, Akureyri, Iceland; died December 25, 2023, Cambridge, Massachusetts, USA) was an Icelandic mathematician whose research focused primarily on harmonic analysis, differential geometry, and Lie group theory.

Helgason obtained his Ph.D. from Princeton University in 1952 under the direction of Salomon Bochner. He held positions at Princeton, the Institute for Advanced Study, Columbia University, and MIT, where he was a professor of mathematics from 1965 until his retirement.

His work is particularly notable for its contributions to integral geometry and representation theory, especially the study of symmetric spaces and their connections to Lie groups. He is the author of numerous influential books on these subjects, including "Differential Geometry, Lie Groups, and Symmetric Spaces," "Groups and Geometric Analysis," and "Geometric Analysis on Symmetric Spaces." These books are considered standard references in the field and have greatly influenced the development of modern harmonic analysis and related areas.

Helgason's research has been recognized with several awards and honors. He was a Guggenheim Fellow and a member of the American Academy of Arts and Sciences. His work has significantly impacted the understanding of the geometry and analysis of homogeneous spaces.