Llewellyn Thomas

Llewellyn Hilleth Thomas was a British physicist and applied mathematician, born in London in 1903 and educated at Cambridge, who is best known for work in atomic and molecular physics. He proposed the relativistic correction now called Thomas precession in 1926 and devised the statistical Thomas-Fermi model of many-electron systems. In computing his name survives in the Thomas algorithm, an efficient method for solving tridiagonal systems of linear equations that is a specialised form of Gaussian elimination. After a professorship at Ohio State University he joined the Watson Scientific Computing Laboratory at Columbia University in 1946, and in 1963 he became the first IBM Fellow at the Watson Research Center. He was elected to the National Academy of Sciences in 1958 and later taught at North Carolina State University, where he retired in 1976.