Daniel Quillen (born 1940) is an American mathematician. He received his Phd from Havard University under the direction of Raoul Bott. He is the main architect of higher algebraic K-theory?. He received the Fields Medal in 1978.
In 1967, he introduced model structures? for abstract homotopical algebra?, an extension of homological algebra. In 1969, he showed that the coefficient ring of complex cobordism? is isomorphic to the Lazard ring? of the universal formal group law?. In 1971, he solved the Adams conjecture on the image of the J-homomorphism?. Quillen is the first architech of rational homotopy theory?, followed by Denis Sullivan?.