HELGASON, Sigurdur
Professor of Mathematics
Age 96, of Belmont, Massachusetts, passed away on December 3, 2023. He was born in Akureyri in 1927, the largest town in northern Iceland with a population of 3100. During his life, he traveled and lived in many parts of the world, but he remained a “boy from Akureyri”.
From a very early age, Sigurdur was enthralled with mathematics. As a child, he enjoyed measuring circular objects around his home to calculate
Pi. In 1940, Akureyri was occupied by the British, an event he remembered keenly. During these years, he sold newspapers (“War News”) to British soldiers. His summers were spent working on a farm, or working in a herring factory north of Akureyri. He finished secondary school in
1945, then studied at the University of Iceland in Reykjavík, before moving to Denmark in 1946 to study mathematics at the University of Copenhagen. In Copenhagen, he developed a love of Denmark and made many friends, with whom he remained close to until the end of his life.
In 1952, he came to the United
States on a Fulbright grant to pursue a doctorate in mathematics at Princeton University, earning his PhD in 1954. He met his future wife, Artie, in 1953 at a dance at Bryn Mawr College, where she was earning her masters in social work. They married four years later on June 9, 1957.
Following teaching positions at Massachusetts Institute of Technology (MIT), Princeton, University of Chicago and Columbia University, he took a faculty position at MIT where he remained for over 60 years, apart from several sabbaticals at the Institute for Advanced Study, the Swedish Institute Mittag-Leffler, and the University of Copenhagen.
Sigurdur’s contributions to the field of mathematics are considerable. In 1962, he wrote “Differential Geometry and Symmetric Spaces”, a text that influenced many mathematicians. This was followed by the equally influential “Differential Geometry”, “Lie Groups” and “Symmetric Spaces” in 1978. His own research contributions included the Plancherel and Paley-Wiener theorems for Riemannian symmetric spaces. Later, he helped create the modern theory of Radon Transforms. During his career, he advised 17 doctoral students and mentored many more.
He held honorary doctorates from the University of Copenhagen, the University of Iceland and Uppsala University and received numerous awards, including the American Mathematical Society’s Steele Prize in 1988. In 1970, he became a fellow of the American Academy of Arts and Sciences and in 2012, a fellow of the American Mathematical Society.
A self-taught pianist, Sigurdur played almost daily up until the day before he died. An avid and skilled chess player, he was an early adopter of computer chess, starting with the (now-obsolete) “Chess Challenger”. He particularly enjoyed playing chess with his grandson during the many family gatherings held at his home. He was also an enthusiastic photographer, capturing images of the unique and beautiful parts of Iceland, as well as the more prosaic close-ups of the resident cardinal on his bird feeder in Belmont.
Countless Icelandic students and musicians who came to study in Boston knew Sigurdur as the unofficial “consulate”. He extended remarkable hospitality to them and his home in Belmont was the “home away from home” for many Icelanders. It was a rare Thanksgiving, Christmas or Easter without at least one Icelandic student joining the celebration.
He remained very close to his family and friends in Iceland, and made many extended visits. On his 80th birthday in 2007, he chaired a conference in Reykjavik entitled “International Conference on Integral Geometry, Harmonic Analysis and Representation Theory”. During breaks in the conference, he enjoyed bringing his colleagues to see the beautiful sights in his home country.
He is survived by his wife of 66 years, Artie Helgason (Gianopulos); son, Thor Helgason and daughterin-law, Lisa Helgason (Johnson); daughter, Dr. Anna Loa Helgason and son-in-law, Mike Jones; and grandchildren, Anders and Brandon Helgason and Ruby and Molly Jones. He was predeceased by his parents, Helgi Skúlason (1892-1983) and Kara Briem (1900-1982); his brother, Skúli Helgason (1926-1973); and his sister, Sigridur Helgadóttir (1933-2003).
Friends are cordially invited to a remembrance of his life, which will be held at 4 pm on January 20, 2024 at the Scandinavian Living Center, in Newton, Massachusetts. swdfuneralhome.com