William Edward Caswell (June 22, 1947 – September 11, 2001) was an American physicist who died during the

September 11 attacks The September 11 attacks, commonly known as 9/11, were four coordinated suicide terrorist attacks carried out by al-Qaeda against the United States on Tuesday, September 11, 2001. That morning, nineteen terrorists hijacked four commercia ...

, as a passenger aboard

American Airlines Flight 77 American Airlines Flight 77 was a scheduled American Airlines domestic transcontinental passenger flight from Washington Dulles International Airport in Dulles, Virginia, to Los Angeles International Airport in Los Angeles, California. The Boe ...

, which was crashed into the

Pentagon In geometry, a pentagon (from the Greek πέντε ''pente'' meaning ''five'' and γωνία ''gonia'' meaning ''angle'') is any five-sided polygon or 5-gon. The sum of the internal angles in a simple pentagon is 540°. A pentagon may be simpl ...

. Caswell did work in

quantum gauge theory In physics, a gauge theory is a type of field theory in which the Lagrangian (and hence the dynamics of the system itself) does not change (is invariant) under local transformations according to certain smooth families of operations (Lie groups ...

, 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 In mathematics and computer science, computer algebra, also called symbolic computation or algebraic computation, is a scientific area that refers to the study and development of algorithms and software for manipulating mathematical expressions ...

Personal life and background

William Edward Caswell was born on June 22, 1947William E. Caswell
Memorial Guide: National 9/11 Memorial. Retrieved October 28, 2011."Biographies: William E. Caswell"

National 9/11 Pentagon Memorial The Pentagon Memorial, formally the National 9/11 Pentagon Memorial, located just southwest of The Pentagon in Arlington County, Virginia, across the Potomac River from Washington, D.C., is a permanent outdoor memorial to the 184 people who die ...

. Retrieved September 11, 2013. in Boston, Massachusetts, the eldest of six children. He lived most of his life in

Silver Spring, Maryland Silver Spring is a census-designated place (CDP) in southeastern Montgomery County, Maryland, United States, near Washington, D.C. Although officially unincorporated, in practice it is an edge city, with a population of 81,015 at the 2020 censu ...

, residing there until his death. He and his wife, Jean, had a daughter.

Education

Caswell attended the

University of Maryland The University of Maryland, College Park (University of Maryland, UMD, or simply Maryland) is a public land-grant research university in College Park, Maryland. Founded in 1856, UMD is the flagship institution of the University System of M ...

and graduated

Phi Beta Kappa The Phi Beta Kappa Society () is the oldest academic honor society in the United States, and the most prestigious, due in part to its long history and academic selectivity. Phi Beta Kappa aims to promote and advocate excellence in the liberal a ...

in three years with a degree in physics in 1968. He then attended graduate school for physics at

Princeton University Princeton University is a private university, private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial Colleges, fourth-oldest ins ...

. His work at Princeton was delayed when he was drafted into the

Army An army (from Old French ''armee'', itself derived from the Latin verb ''armāre'', meaning "to arm", and related to the Latin noun ''arma'', meaning "arms" or "weapons"), ground force or land force is a fighting force that fights primarily on ...

during the

Vietnam War The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...

, where he came to admire the

drill sergeant A drill instructor is a non-commissioned officer in the armed forces, fire department, or police forces with specific duties that vary by country. Foot drill, military step, and marching are typically taught by drill instructors. Australia Austr ...

to whom he was assigned for

basic training Military recruit training, commonly known as basic training or boot camp, refers to the initial instruction of new military personnel. It is a physically and psychologically intensive process, which resocializes its subjects for the unique deman ...

. 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 Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is consider ...

and

Brown University Brown University is a private research university in Providence, Rhode Island. Brown is the seventh-oldest institution of higher education in the United States, founded in 1764 as the College in the English Colony of Rhode Island and Providenc ...

Career

With his thesis advisor

Curtis Callan Curtis Gove Callan Jr. (born October 11, 1942) is an American theoretical physicist and the James S. McDonnell Distinguished University Professor of Physics at Princeton University. He has conducted research in gauge theory, string theory, inst ...

, Caswell embarked on an ambitious program for the summation of

Feynman loop Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the superflu ...

s in order to calculate

elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include electrons, the fundamental fermions ( quarks, leptons, an ...

properties. His thesis, published in 1974, was groundbreaking work that encouraged and shaped future research. To quote his obituary in ''Physics Today'': "Today the interpretation of many experiments in high-energy physics requires multiloop quantum chromodynamics calculations, and Bill's result is a prime ingredient in every such calculation. It is also a critical ingredient in calculating the running of the coupling constants of the Standard Model's supersymmetric extensions, calculations that are interpreted these days as evidence for both grand unification and low-energy supersymmetry. Thus Bill's work is also crucial to our thinking about physics beyond the Standard Model." Caswell did work in

. His graduate career coincided with the synthesis of

gauge symmetry In physics, a gauge theory is a type of field theory in which the Lagrangian (and hence the dynamics of the system itself) does not change (is invariant) under local transformations according to certain smooth families of operations (Lie groups) ...

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 ''Physics Today'' is the membership magazine of the American Institute of Physics. First published in May 1948, it is issued on a monthly schedule, and is provided to the members of ten physics societies, including the American Physical Society. I ...

'', this effort "required unusual courage and determination, since the calculation simultaneously features all the notorious subtleties of gauge invariance, overlapping divergences, and renormalization." In the age of punchcards, FORTRAN and paper output, Caswell felt that pure hand calculation was excruciating to perform and impractical to check. Looking into the then-uncharted world of machine symbolic calculation, he adapted Tony Hearn's REDUCE program in order to graph out calculations. Today his work is utilized in the multiloop quantum chromodynamics calculations that are used in high-energy physics experiments. Caswell and Peter Lepage did significant work in 1978 to develop new and powerful tools for dealing with bound states such as

positronium Positronium (Ps) is a system consisting of an electron and its antimatter, anti-particle, a positron, bound together into an exotic atom, specifically an onium. Unlike hydrogen, the system has no protons. The system is unstable: the two parti ...

and

charmonium In particle physics, quarkonium (from quark and -onium, pl. quarkonia) is a flavorless meson whose constituents are a heavy quark and its own antiquark, making it both a neutral particle and its own antiparticle. Light quarks Light quarks ( up ...

. Caswell was an assistant professor at Brown University from 1977 to 1979, and an assistant professor at the University of Maryland from 1979 to 1983. In 1983, Caswell left academic work for a position as a civilian scientist in the

Naval Surface Weapons Center * A Naval Surface Warfare Center (NSWC) is part of the Naval Sea Systems Command (NAVSEA) operated by the United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the ...

, first at

White Oak, Maryland White Oak is a census-designated place and an unincorporated area in Montgomery County, Maryland, United States. It had a population of 16,347 in 2020. White Oak was known for its Naval Ordnance Laboratory, which was closed in 1994. The headquar ...

, formerly the

Naval Ordnance Laboratory The Naval Ordnance Laboratory (NOL) was a facility in the White Oak area of Montgomery County, Maryland. It is now used as the headquarters of the U.S. Food and Drug Administration. Origins The U.S. Navy Mine Unit, later the Mine Laboratory at t ...

. In 1985, he joined a major classified defense technology project and rose to a position of technical responsibility, directing a team of more than 100 scientists.

Death and legacy

Caswell was on

which was crashed into the Pentagon on September 11, 2001. At the

National September 11 Memorial The National September 11 Memorial & Museum (also known as the 9/11 Memorial & Museum) is a memorial and museum in New York City commemorating the September 11 attacks of 2001, which killed 2,977 people, and the 1993 World Trade Center bombi ...

, he is memorialized at the South Pool, on Panel S-70. His parents were involved in the design of a memorial to 9/11 victims in

Rockville, Maryland Rockville is a city that serves as the county seat of Montgomery County, Maryland, and is part of the Baltimore–Washington metropolitan area. The 2020 census tabulated Rockville's population at 67,117, making it the fifth-largest community in ...

References

External links

Caswell's thesis work, 1974

Obituary in Physics Today

Washington Post obituary

National Pentagon Memorial
* {{DEFAULTSORT:Caswell, William E. 1947 births 2001 deaths 20th-century American physicists 21st-century American physicists American Airlines Flight 77 Brown University faculty People from Silver Spring, Maryland People murdered in Virginia Princeton University alumni Scientists from Maryland Terrorism deaths in Virginia United States Army personnel of the Vietnam War United States Army soldiers United States Navy civilians University of Maryland, College Park alumni University of Maryland, College Park faculty Victims of the September 11 attacks