(1931- ) Dutch Quantum Field Theorist, Particle Physicist
Martinus J. G. Veltman is a pioneer in the development of the quantum field theoretic gauge theories of particle physics. He shared the 1999 Nobel Prize in physics with his former student, gerard’t hooft, for work they did in 1971, which proved that the quantum field theoretic structure of gauge theories, undergoing spontaneous symmetry breaking interactions with a Higgs scalar field, was renormalizable. Veltman’s development of his “Schoonschip” symbolic manipulation computer program, which alge braically simplified the complicated Feynman diagrammatic equations found in quantum field theories, was the foundation of this work.
Veltman was born on June 27, 1931, in the small town of Waalwijjk, in the south of the Netherlands, the fourth of what would become a six-child family. Veltman considers himself the inheritor of both the practicality of his mother’s family of tradespeople and the stu-diousness of his father’s family of pedagogues. Veltman’s father was head of the local primary school, a comfortable position that exempted his family from the hardships of the Depression years. Veltman saw the German army marching in, as they invaded his country in 1940, and remembers how they requisitioned his father’s school for the billeting of soldiers. He was fond of playing with the ammunition left carelessly about by Allied troops but somehow survived this pastime, as well as the bombing of his hometown; the memory of that carnage would remain with him. Liberated in the fall of 1944, the southern part of the Netherlands escaped the brutal winter of 1944-1945, in which many Dutch people died of hunger.
In the midst of the war, in 1943, Veltman entered high school, where conditions, as he put it, “were marked by irregularities,” such as the substitution of a horse stable for a more conventional classroom. During these years he learned about electronics from the local plumber and became the town radio repairman. But his academic performance declined as a result of his lack of aptitude for foreign languages. In 1948, at the age of 17, he narrowly passed his final examinations.
Through the benevolent intervention of his high school physics teacher, Veltman’s parents were persuaded to send him to the University of Utrecht, a 90-minute commute from his home. He made the round trip regularly for three years, although the teaching of physics there, in the difficult postwar years, when many physicists had been killed or had left the country, was uninspiring. He then moved to Utrecht, supporting himself meagerly by typing lectures notes but generally happy in his life of “mainly bumming around.” He took five years, rather than the usual three, to pass his candidate’s exam.
At this point, a revelation occurred to him in the form of a popular book on the theory of relativity—a subject that had not been touched upon in his physics courses. He obtained a copy of albert einstein’s The Meaning of Relativity, and from then on he was “hooked.” While supporting himself as a part-time teacher at a lower technical school, teaching physics to plumbers, he embarked on graduate studies in physics.
Veltman began studying experimental physics but soon realized that this was not his “real destiny.” He switched to theoretical work with Leon Van Hove in 1955 but was soon interrupted by two years of military service. When he returned to the university in February 1959, Van Hove took him on as his Ph.D. student, despite his “relatively advanced age” of 27. Since Van Hove did statistical mechanics and Veltman wanted to do particle physics, he supplemented his education by attending summer schools in Naples and Edinburgh.
In 1961, he followed Van Hove to the European Center for Nuclear Research (CERN), in Geneva. He had married his wife, Anneke, in 1960, and she remained in the Netherlands for the birth of their daughter, Helene (who would one day do a thesis on particle physics at Berkeley), before joining him. In Geneva, Veltman completed a dissertation on both unstable particles and Coulomb corrections to the production of vector bosons produced by neutrinos, which earned him the Ph.D. from Utrecht in 1963. While at CERN, Veltman became deeply involved with the neutrino experiments being conducted there and was spokesperson for the group at the Brookhaven Conference in 1963. The experience left him with a lasting fascination for experiments.
Veltman’s development of his “Schoonschip” symbolic computer program, while at the Stan ford Linear Accelerator (SLAC) in Stanford in 1963, was a direct response to the frustration he and colleagues had felt at the work involved in doing error-free algebraic calculations for vector boson production. He returned to CERN in 1964 and remained there until just after the birth of his son, Hugo, in 1966, after which he spent a short period at the Brookhaven National Laboratory.
Veltman then returned to the University of Utrecht, where he succeeded Van Hove as professor of theoretical physics and began building up the particle physics group, which thrived under his leadership. Hoping to alleviate his relative isolation, he took over as editor of Physics Letters but quit after two years, oppressed by the large amount of “junk” he received and felt obliged to reject.
In the scholarly quiet of a one-month visit in April 1968 to Rockefeller University, Velt-man began the work he would successfully complete back at Utrecht, in 1971, with his doctoral student, Gerard ‘t Hooft. When “Tini,” as everyone called Veltman, took ‘t Hooft on as his student, the first material he gave him to study was a 1950 paper by chen ning yang and Robert Mills, telling him, “This stuff you must know.” Yang and Mills had shown that the quantum electrodynamic (QED) formalism developed earlier by julian seymour schwinger, richard phillips feynman, and sin-itiro tomonaga could be generalized to include internal dynamic symmetries that were more general than the standard spacetime C (charge), P (parity), and T (time-reversal) symmetries.
In the early 1960s, sheldon lee glashow, abdus salam, and steven weinberg used this new generalization of QED to unify the elec-troweak forces into one quantum field theoretic formalism. At the heart of their quest was the fascinating phenomenon of so-called broken symmetries—asymmetric relations that have spontaneously arisen from the functioning of symmetrical laws (e.g., the asymmetric crystal structure of ice that freezes out from the symmetric liquid structure of water when the temperature becomes low enough)—that seem to permeate matter.
They were aware that in the early 1960s Peter Higgs had published papers demonstrating that spontaneous symmetry breaking events associated with coupling to a scalar field could create new kinds of force-carrying particles, some of them massive. This led them to speculate that if the virtual particles that carry the electromagnetic and weak forces (known collectively as the intermediate vector boson W and Z particles) were related by such a broken symmetry, it might be possible to estimate their masses in terms of the unified, more symmetrical force from which the two forces were thought to have arisen. Working independently, each constructed a unified quantum field theory of electromagnetic and weak interactions (i.e., a quantum electroweak theory) that could make a verifiable prediction of the approximate masses of the triplet W and singlet Z particles needed to describe the weak interactions. However, at first, physicists ignored the electroweak theory, which, when used to calculate the properties of the W and Z particles and other physical quantities, predicted nonsensical infinite results.
Meanwhile, in the Netherlands, Veltman had not given up hope of renormalizing theories like the electroweak theory. Twenty years earlier, Feynman had systematized the calculation problem with his diagrams. Veltman hoped to find a way of renormalizing the theory by using “Schoonschip,” which was capable of performing algebraic simplifications of the complicated expressions that all quantum field theories result in when quantitative calculations are made. When ‘t Hooft chose a topic for his Ph.D. thesis in 1969, he chose to apply himself to the problem Veltman was working on: renormalization of the so-called Yang-Mills non-Abelian gauge field theories, which at the time were being applied to the study of the weak interactions.
In 1971, ‘t Hooft succeeded in this task and published two articles describing his break through. However, it was the second paper, in which he renormalized massless Yang-Mills fields for theories by using Higgs spontaneous symmetry breaking mechanism to generate the masses of the fields, that attracted world attention. After using Veltman’s computer program to verify ‘t Hooft’s results, the two men were able to work out a detailed calculation of the renormal-ization method. Using spontaneous symmetry breaking, the renormalized non-Abelian gauge theory of electroweak interaction was now a functioning theoretical machinery capable of performing precise calculations. They presented their results at a 1971 international particle physics conference in Amsterdam.
The impact was enormous. From 1971 on, all theories for the weak interactions that were proposed were Yang-Mills theories that used spontaneous symmetry breaking, and over the next decade it became clear that the Glashow, Weinberg, and Salam’s model was correct. The decisive experiments were first made by carlo rubbia and his team at CERN in 1981. Two years later, in 1983, they announced the discovery of the triplet W and singlet Z particles, which was based on signals from detectors specially designed for this purpose.
Veltman and ‘t Hooft went on to calculate the mass of the top quark, the heavier of the two quarks in the third family of the Standard Model. Many years later, in 1995, the top quark was observed directly for the first time at the Fermi Laboratory in Batavia, Illinois. Another highly important element of the model is the existence of a massive Higgs particle responsible for the spontaneous symmetry breaking, which has not yet been observed. Physicists hope that the Large Hadron Collider (LHC), to be completed at CERN around 2005, will succeed in finding it.
As Veltman and ‘t Hooft both moved on to different research interests, their collaboration dissolved. Then, in 1981, after spending a sabbatical at the University of Michigan in Ann Arbor, Veltman decided to accept the university’s offer to remain there. From 1981 to 1996, Veltman occupied the John D. and Catherine MacArthur Chair, working on gauge theories and their applications to elementary particle physics. In particular he studied radiative corrections in the Standard Model, the Higgs sector and its relationship to the vacuum structure in quantum field theories, and the implications for phenomenology and for new physics beyond the Standard Model. While in the United States, he served on experiment-planning committees at the big laboratories—SLAC, Brookhaven, and the Fermi Laboratory in Batavia, Illinois.
Upon retiring in 1996, Veltman became professor emeritus at Michigan and retired with his wife to the town of Bilthoven in the Netherlands, where they had previously lived.
Veltman’s landmark achievement made it possible for physicists to use gauge theories to make specific predictions of particle properties capable of experimental verification. Ultimately, it was the tool that validated the Wein-berg-Glashow-Salam electroweak theory.
