Jacob David Tamarkin (Russian: Я́ков Дави́дович Тама́ркин, Yakov Davidovich Tamarkin; 11 July 1888 – 18 November 1945) was a Russian-American mathematician best known for his work in mathematical analysis.
Tamarkin was born in Chernigov, Imperial Russia (now Chernihiv, Ukraine) to a wealthy Jewish family. His father, David Tamarkin, was a physician and his mother, Sophie Krassilschikov, was from a family of a landowner. He moved to St Petersburg as a child and grew up there. In his gymnasium he befriended Alexander Friedmann, a cosmologist, with whom he wrote his first mathematics paper in 1906, and remained friends and colleagues until Friedmann's sudden death in 1925. Vladimir Smirnov was his other friend from the same gymnasium. Many years later, they coauthored a popular textbook titled, "A course in higher mathematics".
Tamarkin studied in St Petersburg University where he defended his dissertation in 1917. His advisor was Andrei Markov. After the graduation, Tamarkin worked at Communication Institute and Electrotechnical Institute. In 1919 he temporarily became a professor and a dean at Perm State University, but a year later returned to St Petersburg where he received a professorship at St Petersburg Polytechnical University.
In 1925 he became worried about Russia's stability and decided to emigrate to the United States. His favorite memory was the examination in analytic geometry he had to do with an American consul in Riga, when he tried to prove his identity. In the U.S., he became a lecturer at Dartmouth College. In 1927, Tamarkin received a professorship at Brown University where he remained until his retirement in 1945, after suffering a heart attack. He died later that year in Bethesda, Maryland, a suburb of Washington, D.C.
Tamarkin's work spanned a number of areas, including number theory, integral equations, Fourier series, complex analysis, moment problem, boundary value problem and differential equations. He was a proponent and a founding co-editor of the Mathematical Reviews (which was based at Brown at that time), together with Otto Neugebauer and William Feller. He was also an active supporter of the American Mathematical Society, a member of the council starting 1931, and a vice-president in 1942-43. He had over twenty doctoral students at Brown, including Dorothy Lewis Bernstein, Nelson Dunford, George Forsythe and Derrick Lehmer.