# Gerard T. Hooft

Wolf Prize Laureate in Physics 1981

**Gerard T. Hooft**

#### Affiliation at the time of the award:

**University of Utrecht, The Netherlands**

#### Award citation:

**“for their outstanding contributions to theoretical physics, especially in the development and application of the quantum theory of, fields”.**

#### Prize share:

**Gerard T. Hooft**

**Victor J. Weisskopf**

**Freeman J. Dyson**

Professor Gerard T. Hooft has made a major contribution to the revival of quantum field theory as an essential part of our understanding of elementary particle interactions. Following earlier work by his thesis advisor, M. Veltman, in 1971 T. Hooft showed that infinities could be eliminated by renormalization in theories with spontaneously broken gauge symmetries, such as the electroweak theory of Weinberg and Salam. Together with Veltman, he then systematically developed the mathematical background for calculations in such theories, including especially the method of dimensional regularization, which has been of great value in many areas; including even quantum gravity. T. Hooft also showed how dimensional regularization could serve as the basis for renormalization group calculations, by the so-called “minimum substraction” technique. He then went on to do ground breaking work on a number of topics. He laid the foundation for systematic calculations of instanton effects, including the striking effect of baryon nonconservation. He revived interest in magnetic monopoles by showing that these particles are necessary consequences of a wide variety of gauge theories. He initiated a new approach to the calculation of physical quantities in gauge theories of strong interactions, by the “large N” approximation. Most recently, he has developed methods for deciding what sorts of, massless bound states may be expected to occur in various gauge theories, providing a mathematical basis for speculations about composite particle models of quarks and leptons. A large part of the theoretical physics of the 1970´s has been based on the seminal papers of T. Hooft.