Llewellyn Hilleth Thomas (21 October 1903 – 20 April 1992) was a British

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

and

applied mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

. 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 In physics, the Thomas precession, named after Llewellyn Thomas, is a relativistic correction that applies to the spin of an elementary particle or the rotation of a macroscopic gyroscope and relates the angular velocity of the spin of a pa ...

), 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 In numerical linear algebra, the tridiagonal matrix algorithm, also known as the Thomas algorithm (named after Llewellyn Thomas), is a simplified form of Gaussian elimination that can be used to solve tridiagonal systems of equations. A tridiagona ...

Life and education

Born in London, he studied at

Cambridge University The University of Cambridge is a Public university, public collegiate university, collegiate research university in Cambridge, England. Founded in 1209 and granted a royal charter by Henry III of England, Henry III in 1231, Cambridge is the world' ...

, 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 The Ohio State University, commonly called Ohio State or OSU, is a public land-grant research university in Columbus, Ohio. A member of the University System of Ohio, it has been ranked by major institutional rankings among the best publ ...

, 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 Aberdeen Proving Ground (APG) (sometimes erroneously called Aberdeen Proving ''Grounds'') is a U.S. Army facility located adjacent to Aberdeen, Harford County, Maryland, United States. More than 7,500 civilians and 5,000 military personnel work a ...

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 Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistr ...

, which takes into account the relativistic

time dilation In physics and relativity, time dilation is the difference in the elapsed time as measured by two clocks. It is either due to a relative velocity between them ( special relativistic "kinetic" time dilation) or to a difference in gravitational ...

between the

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

and the

atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron ...

. The Thomas–Fermi model is a statistical model for electron-

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

interactions, which later formed the basis of

density functional theory Density-functional theory (DFT) is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body ...

. The Thomas collapse is effect in few-body physics, which corresponds to infinite value of the three body

binding energy In physics and chemistry, binding energy is the smallest amount of energy required to remove a particle from a system of particles or to disassemble a system of particles into individual parts. In the former meaning the term is predominantly use ...

for zero-range potentials. In mathematics, his name is frequently attached to an efficient Gaussian elimination method for tridiagonal matrices—the Thomas algorithm.

Notable publications

* ''Thomas L. H.'' The motion of the spinning electron // Nature. — 1926. — Vol. 117. — P. 514. �
doi:10.1038/117514a0
* ''Thomas L. H.'' The calculation of atomic fields // Mathematical Proceedings of the Cambridge Philosophical Society. — 1927. — Vol. 23. — P. 542—548. — do
10.1017/S0305004100011683
* ''Thomas L. H.'' The kinematics of an electron with an axis // Philosophical Magazine. — 1927. — Vol. 3. — P. 1—22. — do
10.1080/14786440108564170
* ''Thomas L. H.'' Radiation field in a fluid in motion // Quarterly Journal of Mathematics. — 1930. — Vol. 1. — P. 239—251. — do
10.1093/qmath/os-1.1.239
* ''Thomas L. H.'' The interaction between a neutron and a proton and the structure of H³ // Physical Review. — 1935. — Vol. 47. — P. 903—909. — do
10.1103/PhysRev.47.903
* ''Thomas L. H.'' The paths of ions in the cyclotron I. Orbits in the magnetic field // Physical Review. — 1938. — Vol. 54. — P. 580—588. — do
10.1103/PhysRev.54.580
* ''Shaffer W. H., Nielsen H. H., Thomas L. H.'' The rotation-vibration energies of tetrahedrally symmetric pentatomic molecules. I // Physical Review. — 1939. — Vol. 56. — P. 895—907. — do
10.1103/PhysRev.56.895
* ''Thomas L. H.'' A Practical Method for the Solution of Certain Problems in Quantum Mechanics by Successive Removal of Terms from the Hamiltonian by Contact Transformations of the Dynamical Variables Part I. General Theory // Journal of Chemical Physics. — 1942. — Vol. 10. — P. 532—537. — do
10.1063/1.1723760
* ''Thomas L. H.'' Note on Becker's Theory of the Shock Front // Journal of Chemical Physics. — 1944. — Vol. 12. — P. 449—453. — do
10.1063/1.1723889
* ''Sheldon J., Thomas L. H.'' The use of large scale computing in physics // Journal of Applied Physics. — 1953. — Vol. 24. — P. 235—242. — do
10.1063/1.1721257
* ''Thomas L. H.'' The stability of plane Poiseuille flow // Physical Review. — 1953. — Vol. 91. — P. 780—783. — doi:10.1103/PhysRev.91.780. * ''Bakamjian B., Thomas L. H.'' Relativistic particle dynamics. II // Physical Review. — 1953. — Vol. 92. — P. 1300—1310. — do
10.1103/PhysRev.92.1300
* ''Thomas L. H.'' Satellite Countermeasures // Time. — 1954, May 3. * ''Thomas L. H., Umeda K.'' Atomic Scattering Factors Calculated from the TFD Atomic Model // Journal of Chemical Physics. — 1957. — Vol. 26. — P. 293—303. — do
10.1063/1.1743287

Gallery

File:Nishina Thomas Hund 1926.jpg, Yoshio Nishina,Thomas and Friedrich Hund in Copenhagen in 1926 File:Thomas,Llewellyn 1963 Kopenhagen.jpg, Thomas in Copenhagen in 1963

References

External links