| Ciprian Foias | |
| Birth Name: | Ciprian Ilie Foiaș |
| Birth Date: | 20 July 1933 |
| Birth Place: | Reșița, Caraș County, Kingdom of Romania |
| Death Place: | Tempe, Arizona, United States of America |
| Nationality: | Romanian |
| Fields: | Mathematics |
| Workplaces: | University of Bucharest Institute of Mathematics of the Romanian Academy Paris-Sud University Indiana University Texas A&M University |
| Alma Mater: | University of Bucharest Institute of Mathematics of the Romanian Academy |
| Doctoral Advisor: | Miron Nicolescu |
| Doctoral Students: | Zoia Ceaușescu Adrian Ocneanu Dan-Virgil Voiculescu |
| Known For: | Commutant lifting theorem Foias constant |
| Awards: | Wiener Prize (1995) |
Ciprian Ilie Foiaș (20 July 1933 – 22 March 2020) was a Romanian-American mathematician. He was awarded the Norbert Wiener Prize in Applied Mathematics in 1995, for his contributions in operator theory.
Born in Reșița, Romania, Foiaș studied mathematics at the University of Bucharest. He completed his dissertation in 1957,[1] but was not allowed to defend his thesis by the Communist government until 1962[2] because his father, a respected physician, had been sent to a forced labor camp after the communists came to power.[3] He received his doctorate in 1962 from the Institute of Mathematics of the Romanian Academy (IMAR) under supervision of Miron Nicolescu.
Foias began teaching at the University of Bucharest in 1954.[1] From 1958 to 1978 he was a researcher at IMAR, and from 1966 to 1978 he was a professor in the Faculty of Mathematics at the University of Bucharest.[1] [4] In recognition of his growing international reputation, he was named doctor docent in 1968.
Foias was an invited speaker at the International Congress of Mathematicians (ICM) in Nice in 1970, and again at the ICM in Helsinki in 1978. Following his lecture in Helsinki, he defected to France, and then taught at the University of Paris — XI from 1979 to 1983. He later emigrated to the United States, where he was a professor at Indiana University from 1983 until retirement. Beginning in 2000, he was a teacher and researcher at Texas A&M University, where he was a Distinguished Professor.[1]
Together with Béla Szőkefalvi-Nagy, Foias proved the celebrated commutant lifting theorem. The Foias constant is named after him. Foias is listed as an ISI highly cited researcher.[5] In 1994 he was elected honorary member of the Romanian Academy.[4] [6]
He died in Tempe, Arizona on March 22, 2020.[7] That year, the American Mathematical Society established the Ciprian Foias Prize in Operator Theory, which is awarded every three years.[8]