Gian-Carlo Wick

Gian Carlo Wick (October 15, 1909 – April 20, 1992) was an Italian theoretical physicist who made important contributions to quantum field theory. The Wick rotation, Wick contraction, Wick's theorem, and the Wick product are named after him.

Wick's father was a chemical engineer, and his mother, Barbara Allason (1877–1968), was a well-known Italian writer and anti-fascist. His paternal grandfather had emigrated from Switzerland to Italy and his grandmother from Austria. In 1930 he received his degree in Turin under G. Wataghin with a thesis on the electronic theory of metals, and then went to Göttingen and Leipzig to study physics. One of the professors he got to know there was Werner Heisenberg. Heisenberg liked the young Italian theoretician-they shared a common interest in classic music- and treated him with an affection that Wick never forgot. Once a week, Heisenberg had invited Wick and other students to his home for spirited evenings of talk and Ping-Pong. Back in Turin, he became Enrico Fermi's assistant in Rome in 1932. In 1937 he became professor of theoretical physics in Palermo, then in Padua, before, in 1940, he returned to Rome and became chair of theoretical physics. In 1946 he followed Fermi to the United States, first to the University of Notre Dame, then to Berkeley. Since he refused a required oath during the McCarthy era (he had inherited strong liberal views from his mother), he went to the Carnegie Institute of Technology in Pittsburgh in 1951, where he remained until 1957, interrupted by stays at the Institute for Advanced Study in Princeton and at CERN in Geneva. In 1957 he became chief of the theory department at Brookhaven National Laboratory. In 1965 he became a tenured professor at Columbia University in New York City, where he collaborated with Tsung-Dao Lee; after his retirement from Columbia he worked at the Scuola Normale Superiore in Pisa.

In 1967 he received the Dannie Heineman Prize. In 1968 he received the first Ettore Majorana Prize. He was a member of the United States National Academy of Sciences and the Accademia dei Lincei.

Wick was an avid mountain climber. He was twice married and had two sons.

As a member of Fermi's group in Rome, Wick calculated the magnetic moment of the hydrogen molecule with group-theoretical methods. He extended Fermi's theory of beta decay to positron emission and K-capture, and explained the relationship between the range of a force and the mass of its force carrier particle. He also worked on slowing down of neutrons in matter, and joined a group of Italian physicists led by Gilberto Bernardini which made the first measurement of the lifetime of the muon.

While in the United States, Wick made fundamental contributions to quantum field theory, such as the Wick theorem in 1950, which showed how to express calculations in quantum field theory in terms of normally-ordered products and thus derive Feynman rules. He also introduced the Wick rotation, in which computations are analytically continued from Minkowski space to four-dimensional Euclidean space using a coordinate change to imaginary time He developed the helicity formulation for collisions between particles with arbitrary spin, worked with Geoffrey Chew on the impulse approximation, and worked on meson theory, symmetry principles in physics, and the vacuum structure of quantum field theory.

• Über die Wechselwirkung zwischen Neutronen und Protonen, Zeitschrift für Physik 84, #11–12 (1933), pp. 799–800, doi:10.1007/BF01330504.
• The Evaluation of the Collision Matrix, Physical Review 80 (1950), pp. 268–272, doi:10.1103/PhysRev.80.268.
• Properties of Bethe-Salpeter Wave Functions, Physical Review 96 (1954), pp. 1124–1134, doi:10.1103/PhysRev.96.1124 (introduced the Wick rotation.)
• Introduction to Some Recent Work in Meson Theory, Reviews of Modern Physics 27 (1955), pp. 339–362, doi:10.1103/RevModPhys.27.339.
• (with Maurice Jacob) On the general theory of collisions for particles with spin, Annals of Physics 7, #4 (August 1959), pp. 404–428, doi:10.1016/0003-4916(59)90051-X.
• (with Arthur Strong Wightman and Eugene P. Wigner) Superselection Rule for Charge, Physical Review D 1 (1970), pp. 3267–3269, doi:10.1103/PhysRevD.1.3267.
• (with Tsung-Dao Lee) Vacuum stability and vacuum excitation in a spin-0 field theory, Physical Review D 9 (1974), pp. 2291–2316, doi:10.1103/PhysRevD.9.2291.