Llewellyn Thomas

For other people named Llewellyn Thomas, see Llewellyn Thomas (disambiguation).

Llewellyn Hilleth Thomas
Thomas in Copenhagen, 1926
Born	(1903-10-21)21 October 1903 London, United Kingdom
Died	20 April 1992(1992-04-20) (aged 88) Raleigh, North Carolina, USA
Known for	Thomas precession Thomas algorithm Thomas-Fermi model Thomas-Fermi screening Thomas-Fermi equation Spin–orbit interaction
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)

Llewellyn Hilleth Thomas (21 October 1903 – 20 April 1992) was a British physicist and applied mathematician. 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 hydrogenic atom (Thomas precession), creating an approximate theory of $N$-body quantum systems (Thomas-Fermi theory), and devising an efficient method for solving tridiagonal system of linear equations (Thomas algorithm).

Life and education

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. In 1935 he was the master's thesis advisor for Leonard Schiff, whose thesis was published with Thomas as coauthor. 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. He was appointed professor at North Carolina State University in 1968, retiring from this position in 1976. In 1982 he received the Davisson-Germer Prize. He died in Raleigh, North Carolina.

Contributions

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.

Gallery

• 
  Yoshio Nishina, Thomas, and Friedrich Hund in Copenhagen in 1926
• 
  Thomas in Copenhagen in 1963

See also

• Thomas–Fermi approximation

External links

• Guide to the Llewellyn Hilleth Thomas Papers at the North Carolina State University
• NA-Digest on the attribution of the Thomas Algorithm's name