Llewellyn Hilleth Thomas (21 October 1903 – 20 April 1992) was a British physicist and applied mathematician.[1] He is best known for his contributions to atomic and molecular physics and solid-state physics. His key achievements include calculating relativistic effects on the spin-orbit interaction in a hydrogen atom (Thomas precession), creating an approximate theory of -body quantum systems (Thomas-Fermi theory), and devising an efficient method for solving tridiagonal system of linear equations (Thomas algorithm).
Llewellyn Hilleth Thomas | |
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Born | London, United Kingdom | 21 October 1903
Died | 20 April 1992 Raleigh, North Carolina, USA | (aged 88)
Known for | Thomas precession Thomas algorithm Thomas-Fermi model Thomas-Fermi screening Thomas-Fermi equation |
Awards | Smith's Prize (1925) |
Scientific career | |
Thesis | Contributions to the theory of the motion of electrified particles through matter and some effects of that motion (1927) |
Born in London, he studied at Cambridge University, receiving his BA, PhD, and MA degrees in 1924, 1927 and 1928 respectively. While on a Traveling Fellowship for the academic year 1925–1926 at Bohr's Institute in Copenhagen, he proposed Thomas precession in 1926, to explain the difference between predictions made by spin-orbit coupling theory and experimental observations.
In 1929 he obtained a job as a professor of physics at the Ohio State University, where he stayed until 1943. He married Naomi Estelle Frech in 1933.[2] In 1935 he was the master's thesis advisor for Leonard Schiff, whose thesis was published with Thomas as coauthor.[3] From 1943 until 1945 Thomas worked on ballistics at the Aberdeen Proving Ground in Maryland. In 1946 he became a member of the staff of the Watson Scientific Computing Laboratory at Columbia University, remaining there until 1968. In 1958 he was elected as a member of the National Academy of Sciences. In 1963, Thomas was appointed as IBM's First Fellow in the Watson Research Center.[4] He was appointed professor at North Carolina State University in 1968, retiring from this position in 1976.[2] In 1982 he received the Davisson-Germer Prize.[5] He died in Raleigh, North Carolina.[2][6]
Thomas was responsible for multiple advances in physics. The Thomas precession is a correction to the atomic spin-orbit interaction in quantum mechanics, which takes into account the relativistic time dilation between the electron and the atomic nucleus. The Thomas–Fermi model is a statistical model for electron-ion interactions, which later formed the basis of density functional theory. The Thomas collapse is effect in few-body physics, which corresponds to infinite value of the three body binding energy for zero-range potentials.
In mathematics, his name is frequently attached to an efficient Gaussian elimination method for tridiagonal matrices—the Thomas algorithm.