William E. Caswell

William Edward Caswell (June 22, 1947 – September 11, 2001) was an American physicist. He did work in quantum gauge theory, most notably, his 1972 calculation of the beta function to two-loop accuracy. His pioneering work in the days of FORTRAN and punch cards demonstrated the potential of computer algebra. Caswell died during the September 11 attacks as a passenger aboard American Airlines Flight 77, which was crashed into the Pentagon.

Personal life and background William Edward Caswell was born on June 22, 1947, in Boston, Massachusetts, the eldest of six children. He lived most of his life in Silver Spring, Maryland, residing there until his death.

Education Caswell attended the University of Maryland and graduated Phi Beta Kappa in three years with a degree in physics in 1968. He then attended graduate school for physics at Princeton University. His work at Princeton was delayed when he was drafted into the Army during the Vietnam War, where he came to admire the drill sergeant to whom he was assigned for basic training. When Caswell resumed his studies at Princeton, he chose to work in elementary particle theory. He received his Ph.D. in physics in January 1975, and subsequently did postdoctoral work at Stanford University and Brown University.

Caswell did work in quantum gauge theory. His graduate career coincided with the synthesis of gauge symmetry and renormalization group ideas, in which he himself made several pioneering contributions, the highpoint of which was his 1972 calculation of the beta function to two-loop accuracy. According to Physics Today, this effort "required unusual courage and determination, since the calculation simultaneously features all the notorious subtleties of gauge invariance, overlapping divergences, and renormalization."