Keith Allen Brueckner (born 1924) is a theoretical physicist who has given important contributions in several areas of physics, including many-body theory in condensed matter physics, and laser fusion. He was born in Minneapolis on March 19, 1924. He earned a B.A. and M.A. in mathematics from the University of Minnesota in 1945 and 1947 and a Ph.D. in physics from the University of California, Berkeley, in 1950. After completing his Ph.D. he joined the physics faculty at Indiana University (1951–1955) and then at the University of Pennsylvania (1956–1959). In 1959, Brueckner was recruited by Roger Revelle to come to University of California, San Diego, where he became one of founders the Department of Physics. As Dean of the faculty during the early years of UCSD he was influential in recruiting several of the founding academics of the university.
In a collaboration with Murray Gell-Mann they showed that the random phase approximation (RPA) can be derived by summing up a series of Feynmann diagrams.[1] This was a seminal result at the time, since the relevance and correctness of RPA was heavily debated. This result is often considered to be the first major result of modern quantum many-particle theory and has been important inspiration for an entire field.