Juris Hartmanis

Juris Hartmanis (born July 5, 1928) is a prominent computer scientist and computational theorist who, with Richard E. Stearns, received the 1993 ACM Turing Award "in recognition of their seminal paper which established the foundations for the field of computational complexity theory".
Hartmanis was born in Latvia. He was a son of Mārtiņš Hartmanis, a general in the Latvian Army. After the Soviet Union occupied Latvia in 1940, Mārtiņš Hartmanis was arrested by Soviets and died in a prison. At the end of World War II, the wife and children of Mārtiņš Hartmanis left Latvia as refugees, fearing for their safety if the Soviet Union took over Latvia again.
They first moved to Germany, where Juris Hartmanis received the equivalent of a Master's degree in Physics from the University of Marburg. Then he moved to the United States, where he received Master's degree in Applied Mathematics at the University of Kansas City (now known as the University of Missouri-Kansas City) in 1951 and Ph.D. in Mathematics from Caltech under the supervision of Robert P. Dilworth in 1955. The University of Missouri-Kansas City honored him with Honorary Doctor of Humane Letters in May 1999.
After teaching at Cornell University and Ohio State University, Hartmanis joined the General Electric Research Laboratory in 1958. While at General Electric, he developed many principles of computational complexity theory. In 1965, he became a professor at Cornell University. At Cornell, he was one of founders and the first chairman of its computer science department (which was one of the first computer science departments in the world). Hartmanis is a Fellow of the Association for Computing Machinery and of the American Mathematical Society and a member of the National Academy of Engineering and National Academy of Sciences.
He is best known for his Turing-award winning paper with Richard Stearns, in which he introduced time complexity classes TIME (f(n)) and proved the time hierarchy theorem. Another paper by Hartmanis from 1977, with Leonard Berman, introduced the still-unsolved Berman–Hartmanis conjecture that all NP-complete languages are polynomial time isomorphic.

• Berman, L.; Hartmanis, J. (1977), "On isomorphisms and density of NP and other complete sets", SIAM Journal on Computing, 6 (2): 305–322, doi:10.1137/0206023, MR 0455536 .
• Hartmanis, J.; Stearns, R. E. (1965), "On the computational complexity of algorithms", Transactions of the American Mathematical Society, 117: 285–306, doi:10.2307/1994208, JSTOR 1994208, MR 0170805 .