Gerardus "Gerard" 't Hooft (; born July 5, 1946) is a Dutch
theoretical physicist
Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict natural phenomena. This is in contrast to experimental physics, which uses experi ...
and professor at
Utrecht University
Utrecht University (UU; , formerly ''Rijksuniversiteit Utrecht'') is a public university, public research university in Utrecht, Netherlands. Established , it is one of the oldest universities in the Netherlands. In 2023, it had an enrollment of ...
, the Netherlands. He shared the 1999
Nobel Prize in Physics
The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...
with his thesis advisor
Martinus J. G. Veltman "for elucidating the quantum structure of
electroweak interactions".
His work concentrates on
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 under local transformations according to certain smooth families of operations (Lie groups). Formally, t ...
,
black hole
A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...
s,
quantum gravity
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics. It deals with environments in which neither gravitational nor quantum effects can be ignored, such as in the v ...
and fundamental aspects of quantum mechanics. His contributions to physics include: a proof that
gauge theories
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 under local transformations according to certain smooth families of operations (Lie groups). Formally, t ...
are
renormalizable;
dimensional regularization; and the
holographic principle.
Biography
Early life
't Hooft was born in
Den Helder
Den Helder () is a municipality and a city in the Netherlands, in the province of North Holland. Den Helder occupies the northernmost point of the North Holland peninsula. It is home to the country's main naval base.
From here the Royal TESO fe ...
on July 5, 1946, to Hendrik 't Hooft and Margaretha Agnes 'Peggy' van Kampen, but grew up in
The Hague
The Hague ( ) is the capital city of the South Holland province of the Netherlands. With a population of over half a million, it is the third-largest city in the Netherlands. Situated on the west coast facing the North Sea, The Hague is the c ...
. He was the middle child of a family of three. He comes from a family of scholars. His great uncle was Nobel prize laureate
Frits Zernike; his maternal grandfather was
Pieter Nicolaas van Kampen, a professor of
zoology
Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...
at
Leiden University
Leiden University (abbreviated as ''LEI''; ) is a Public university, public research university in Leiden, Netherlands. Established in 1575 by William the Silent, William, Prince of Orange as a Protestantism, Protestant institution, it holds the d ...
; his uncle
Nico van Kampen
Nicolaas 'Nico' Godfried van Kampen (22 June 1921 – 6 October 2013) was a Dutch theoretical physicist, who worked mainly on statistical mechanics and non-equilibrium thermodynamics.
Van Kampen was born in Leiden, and was a nephew of Frits Zer ...
was an (emeritus) professor of theoretical physics at Utrecht University, and his father was a maritime engineer. Following his family's footsteps, he showed interest in science at an early age. When his primary school teacher asked him what he wanted to be when he grew up, he replied, "a man who knows everything."
After primary school Gerard attended the Dalton Lyceum, a school that applied the ideas of the
Dalton Plan, an educational method that suited him well. He excelled at science and mathematics courses. At the age of sixteen he won a silver medal in the second Dutch
Math Olympiad.
[
]
Education
After 't Hooft passed his high school exams in 1964, he enrolled in the physics program at Utrecht University. He opted for Utrecht instead of the much closer Leiden, because his uncle was a professor there and he wanted to attend his lectures. Because he was so focused on science, his father insisted that he join the Utrechtsch Studenten Corps, a student association, in the hope that he would do something else besides studying. This worked to some extent; during his studies he was a
coxswain
The coxswain ( or ) is the person in charge of a boat, particularly its navigation and steering. The etymology of the word gives a literal meaning of "boat servant" since it comes from ''cock'', referring to the wiktionary:cockboat, cockboat, a ...
with their rowing club "Triton" and organized a national congress for science students with their science discussion club "Christiaan Huygens".
In the course of his studies he decided he wanted to go into what he perceived as the heart of theoretical physics,
elementary particles
In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a con ...
. His uncle had grown to dislike the subject and in particular its practitioners, so when it became time to write his ''doctoraalscriptie'' (former name of the Dutch equivalent of a master's
thesis
A thesis (: theses), or dissertation (abbreviated diss.), is a document submitted in support of candidature for an academic degree or professional qualification presenting the author's research and findings.International Standard ISO 7144: D ...
) in 1968, 't Hooft turned to the newly appointed professor
Martinus Veltman, who specialized in
Yang–Mills theory
Yang–Mills theory is a quantum field theory for nuclear binding devised by Chen Ning Yang and Robert Mills in 1953, as well as a generic term for the class of similar theories. The Yang–Mills theory is a gauge theory based on a special un ...
, a relatively fringe subject at the time because it was thought that these could not be
renormalized. His assignment was to study the
Adler–Bell–Jackiw anomaly, a mismatch in the theory of the decay of neutral
pion
In particle physics, a pion (, ) or pi meson, denoted with the Greek alphabet, Greek letter pi (letter), pi (), is any of three subatomic particles: , , and . Each pion consists of a quark and an antiquark and is therefore a meson. Pions are the ...
s; formal arguments forbid the decay into
photon
A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that can ...
s, whereas practical calculations and experiments showed that this was the primary form of decay. The resolution of the problem was completely unknown at the time, and 't Hooft was unable to provide one.
In 1969, 't Hooft started on his doctoral research with Martinus Veltman as his advisor. He would work on the same subject Veltman was working on, the renormalization of Yang–Mills theories. In 1971 his first paper was published. In it he showed how to renormalize massless Yang–Mills fields, and was able to derive relations between amplitudes, which would be generalized by
Andrei Slavnov and
John C. Taylor, and become known as the
Slavnov–Taylor identities.
The world took little notice, but Veltman was excited because he saw that the problem he had been working on was solved. A period of intense collaboration followed in which they developed the technique of
dimensional regularization. Soon 't Hooft's second paper was ready to be published, in which he showed that Yang–Mills theories with massive fields due to spontaneous symmetry breaking could be renormalized. This paper earned them worldwide recognition, and would ultimately earn the pair the 1999 Nobel Prize in Physics.
These two papers formed the basis of 't Hooft's
dissertation, ''The Renormalization procedure for Yang–Mills Fields'', and he obtained his
PhD
A Doctor of Philosophy (PhD, DPhil; or ) is a terminal degree that usually denotes the highest level of academic achievement in a given discipline and is awarded following a course of graduate study and original research. The name of the deg ...
degree in 1972. In the same year he married his wife, Albertha A. Schik, a student of
medicine
Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...
in Utrecht.
[
]
Career
After obtaining his doctorate 't Hooft went to CERN
The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in Meyrin, western suburb of Gene ...
in Geneva
Geneva ( , ; ) ; ; . is the List of cities in Switzerland, second-most populous city in Switzerland and the most populous in French-speaking Romandy. Situated in the southwest of the country, where the Rhône exits Lake Geneva, it is the ca ...
, where he had a fellowship. He further refined his methods for Yang–Mills theories with Veltman (who went back to Geneva). In this time he became interested in the possibility that the strong interaction
In nuclear physics and particle physics, the strong interaction, also called the strong force or strong nuclear force, is one of the four known fundamental interaction, fundamental interactions. It confines Quark, quarks into proton, protons, n ...
could be described as a massless Yang–Mills theory, i.e. one of a type that he had just proved to be renormalizable and hence be susceptible to detailed calculation and comparison with experiment.
According to 't Hooft's calculations, this type of theory possessed just the right kind of scaling properties ( asymptotic freedom) that this theory should have according to deep inelastic scattering experiments. This was contrary to popular perception of Yang–Mills theories at the time, that like gravitation and electrodynamics, their intensity should decrease with increasing distance between the interacting particles; such conventional behaviour with distance was unable to explain the results of deep inelastic scattering, whereas 't Hooft's calculations could.
When 't Hooft mentioned his results at a small conference at Marseilles in 1972, Kurt Symanzik urged him to publish this result;[ but 't Hooft did not, and the result was eventually rediscovered and published by Hugh David Politzer, ]David Gross
David Jonathan Gross (; born February 19, 1941) is an American theoretical physicist and string theorist. Along with Frank Wilczek and David Politzer, he was awarded the 2004 Nobel Prize in Physics for their discovery of asymptotic freedom. ...
, and Frank Wilczek
Frank Anthony Wilczek ( or ; born May 15, 1951) is an American theoretical physicist, mathematician and Nobel laureate. He is the Herman Feshbach Professor of Physics at the Massachusetts Institute of Technology (MIT), Founding Director ...
in 1973, which led to their earning the 2004 Nobel Prize in Physics
The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...
.
In 1974, 't Hooft returned to Utrecht where he became assistant professor. In 1976, he was invited for a guest position at Stanford and a position at Harvard
Harvard University is a private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of higher lear ...
as Morris Loeb lecturer. His eldest daughter, Saskia Anne, was born in Boston
Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...
, while his second daughter, Ellen Marga, was born in 1978 after he returned to Utrecht, where he was made full professor.[ In the academic year 1987–1988 't Hooft spent a sabbatical in the Boston University Physics Department along with Howard Georgi, Robert Jaffe and others arranged by the then new Department chair Lawrence Sulak.
In 2007 't Hooft became editor-in-chief for '']Foundations of Physics
''Foundations of Physics'' is a monthly journal "devoted to the conceptual bases and fundamental theories of modern physics and cosmology, emphasizing the logical, methodological, and philosophical premises of modern physical theories and procedur ...
'', where he sought to distance the journal from the controversy of ECE theory. 't Hooft held the position until 2016.
On July 1, 2011 he was appointed Distinguished professor by Utrecht University.
Personal life
He is married to Albertha Schik (Betteke) and has two daughters.
Honors
In 1999 't Hooft shared the Nobel prize in Physics with his thesis adviser Veltman for "elucidating the quantum structure of the electroweak interactions in physics".[
] Before that time his work had already been recognized by other notable awards. In 1981, he was awarded the Wolf Prize
The Wolf Prize is an international award granted in Israel, that has been presented most years since 1978 to living scientists and artists for "achievements in the interest of mankind and friendly relations among people ... irrespective of natio ...
, possibly the most prestigious prize in physics after the Nobel prize. Five years later he received the Lorentz Medal
Lorentz Medal is a distinction awarded every four years by the Royal Netherlands Academy of Arts and Sciences. It was established in 1925 on the occasion of the 50th anniversary of the doctorate of Hendrik Lorentz. The medal is given for imp ...
, awarded every four years in recognition of the most important contributions in theoretical physics. In 1995, he was one of the first recipients of the Spinozapremie, the highest award available to scientists in the Netherlands. In the same year he was also honoured with a Franklin Medal. In 2000, 't Hooft received the Golden Plate Award of the American Academy of Achievement
The American Academy of Achievement, colloquially known as the Academy of Achievement, is a nonprofit educational organization that recognizes some of the highest-achieving people in diverse fields and gives them the opportunity to meet one ano ...
.
Since his Nobel Prize, 't Hooft has received a slew of awards, honorary doctorates and honorary professorships.[
] He was knighted commander in the Order of the Netherlands Lion
The Order of the Netherlands Lion, also known as the Order of the Lion of the Netherlands (, ) is a Dutch honours system, Dutch order of chivalry founded by William I of the Netherlands on 29 September 1815.
The Order of the Netherlands Lion wa ...
, and officer in the French Legion of Honor. The asteroid 9491 Thooft has been named in his honor, and he has written a constitution for its future inhabitants.
He is a member of the Royal Netherlands Academy of Arts and Sciences (KNAW) since 1982, where he was made academy professor in 2003. He is also a foreign member of many other science academies, including the French Académie des Sciences, the American National Academy of Sciences
The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...
and American Academy of Arts and Sciences
The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...
and the Britain and Ireland based Institute of Physics
The Institute of Physics (IOP) is a UK-based not-for-profit learned society and professional body that works to advance physics education, physics research, research and applied physics, application.
It was founded in 1874 and has a worldwide ...
.
't Hooft has appeared in season 3 of ''Through the Wormhole
''Through the Wormhole'' is an American science Documentary film, documentary television series narrated and hosted by American actor Morgan Freeman. It began airing on Science Channel in the United States on June 9, 2010. The series concluded i ...
'' with Morgan Freeman.
Research
't Hooft's research interest can be divided in three main directions: 'gauge theories in elementary particle physics', 'quantum gravity and black holes', and 'foundational aspects of quantum mechanics'.
Gauge theories in elementary particle physics
't Hooft is most famous for his contributions to the development of gauge theories in particle physics. The best known of these is the proof in his PhD thesis that Yang–Mills theories are renormalizable, for which he shared the 1999 Nobel Prize in Physics. For this proof he introduced (with his adviser Veltman) the technique of dimensional regularization.
After his PhD, he became interested in the role of gauge theories in the strong interaction, the leading theory of which is called quantum chromodynamics
In theoretical physics, quantum chromodynamics (QCD) is the study of the strong interaction between quarks mediated by gluons. Quarks are fundamental particles that make up composite hadrons such as the proton, neutron and pion. QCD is a type of ...
or QCD. Much of his research focused on the problem of color confinement
In quantum chromodynamics (QCD), color confinement, often simply called confinement, is the phenomenon that color-charged particles (such as quarks and gluons) cannot be isolated, and therefore cannot be directly observed in normal conditions b ...
in QCD, i.e. the observational fact that only color neutral particles are observed at low energies. This led him to the discovery that SU(N) gauge theories simplify in the large ''N'' limit, a fact which has proved important in the examination of the conjectured correspondence between string theories in an Anti-de Sitter space
In mathematics and physics, ''n''-dimensional anti-de Sitter space (AdS''n'') is a symmetric_space, maximally symmetric Lorentzian manifold with constant negative scalar curvature. Anti-de Sitter space and de Sitter space are na ...
and conformal field theories in one lower dimension. By solving the theory in one space and one time dimension, 't Hooft was able to derive a formula for the masses of meson
In particle physics, a meson () is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticles, the ...
s.
He also studied the role of so-called instanton contributions in QCD. His calculation showed that these contributions lead to an interaction between light quark
A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nucleus, atomic nuclei ...
s at low energies not present in the normal theory. Studying instanton solutions of Yang–Mills theories, 't Hooft discovered that spontaneously breaking a theory with SU(N) symmetry to a U(1)
In mathematics, the circle group, denoted by \mathbb T or , is the multiplicative group of all complex numbers with absolute value 1, that is, the unit circle in the complex plane or simply the unit complex numbers
\mathbb T = \.
The circle g ...
symmetry will lead to the existence of magnetic monopoles. These monopoles are called 't Hooft–Polyakov monopoles, after Alexander Polyakov, who independently obtained the same result.
As another piece in the color confinement puzzle 't Hooft introduced 't Hooft loops, which are the magnetic dual of Wilson loop
In quantum field theory, Wilson loops are gauge invariant operators arising from the parallel transport of gauge variables around closed loops. They encode all gauge information of the theory, allowing for the construction of loop representati ...
s. Using these operators he was able to classify different phases of QCD, which form the basis of the QCD phase diagram.
In 1986, he was finally able to show that instanton contributions solve the Adler–Bell–Jackiw anomaly, the topic of his master's thesis.
Quantum gravity and black holes
When Veltman and 't Hooft moved to CERN after 't Hooft obtained his PhD, Veltman's attention was drawn to the possibility of using their dimensional regularization techniques to the problem of quantizing gravity. Although it was known that perturbative quantum gravity
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics. It deals with environments in which neither gravitational nor quantum effects can be ignored, such as in the v ...
was not completely renormalizible, they felt important lessons were to be learned by studying the formal renormalization of the theory order by order. This work would be continued by Stanley Deser and another PhD student of Veltman, Peter van Nieuwenhuizen, who later found patterns in the renormalization counter terms, which led to the discovery of supergravity
In theoretical physics, supergravity (supergravity theory; SUGRA for short) is a modern field theory that combines the principles of supersymmetry and general relativity; this is in contrast to non-gravitational supersymmetric theories such as ...
.
In the 1980s, 't Hooft's attention was drawn to the subject of gravity in 3 spacetime dimensions. Together with Deser and Jackiw he published an article in 1984 describing the dynamics of flat space where the only local degrees of freedom were propagating point defects. His attention returned to this model at various points in time, showing that Gott pairs would not cause causality violating timelike loops, and showing how the model could be quantized. More recently he proposed generalizing this piecewise flat model of gravity to 4 spacetime dimensions.
With Stephen Hawking
Stephen William Hawking (8January 194214March 2018) was an English theoretical physics, theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge. Between ...
's discovery of Hawking radiation
Hawking radiation is black-body radiation released outside a black hole's event horizon due to quantum effects according to a model developed by Stephen Hawking in 1974.
The radiation was not predicted by previous models which assumed that onc ...
of black hole
A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...
s, it appeared that the evaporation of these objects violated a fundamental property of quantum mechanics, unitarity. 't Hooft refused to accept this problem, known as the black hole information paradox, and assumed that this must be the result of the semi-classical treatment of Hawking, and that it should not appear in a full theory of quantum gravity. He proposed that it might be possible to study some of the properties of such a theory, by assuming that such a theory was unitary.
Using this approach he has argued that near a black hole, quantum fields could be described by a theory in a lower dimension. This led to the introduction of the holographic principle by him and Leonard Susskind
Leonard Susskind (; born June 16, 1940)his 60th birth anniversary was celebrated with a special symposium at Stanford University.in Geoffrey West's introduction, he gives Suskind's current age as 74 and says his birthday was recent. is an Americ ...
.
Fundamental aspects of quantum mechanics
't Hooft has "deviating views on the physical interpretation of quantum theory". He believes that there could be a deterministic
Determinism is the metaphysical view that all events within the universe (or multiverse) can occur only in one possible way. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes overlapping mo ...
explanation underlying quantum mechanics. Using a speculative model he has argued that such a theory could avoid the usual Bell inequality arguments that would disallow such a local hidden-variable theory. In 2016 he published a book length exposition of his ideas which, according to 't Hooft, has encountered mixed reactions.
Popular publications
*
*
*
Academic publications
*
See also
* Asymptotic freedom
* Center vortex
* Hierarchy problem
* Pauli–Villars regularization
* Slavnov–Taylor identities
* Superdeterminism
* Mars One (Gerard 't Hooft is a main supporter of the project)
References
External links
Gerard 't Hooft
(homepage)
How To Become a Good Theoretical Physicist
* including the Nobel Lecture ''A Confrontation with Infinity''
Publications
from Google Scholar
Google Scholar is a freely accessible web search engine that indexes the full text or metadata of Academic publishing, scholarly literature across an array of publishing formats and disciplines. Released in Beta release, beta in November 2004, th ...
Publications
on the arXiv
arXiv (pronounced as "archive"—the X represents the Chi (letter), Greek letter chi ⟨χ⟩) is an open-access repository of electronic preprints and postprints (known as e-prints) approved for posting after moderation, but not Scholarly pee ...
TVO.org video – Gerard t'Hooft lectures on Science Fiction and Reality
Lecture delivered at the Perimeter Institute in Waterloo, Ontario, Canada on May 7, 2008
*
{{DEFAULTSORT:Hooft, Gerardus t
1946 births
Living people
20th-century Dutch physicists
Members of the Royal Netherlands Academy of Arts and Sciences
Foreign associates of the National Academy of Sciences
Foreign members of the Russian Academy of Sciences
Nobel laureates in Physics
Dutch Nobel laureates
Utrecht University alumni
Academic staff of Utrecht University
Wolf Prize in Physics laureates
Commanders of the Order of the Netherlands Lion
Officers of the Legion of Honour
Lorentz Medal winners
Recipients of the Lomonosov Gold Medal
People from Den Helder
Scientists from Utrecht (city)
Members of the French Academy of Sciences
Institute for Advanced Study visiting scholars
Spinoza Prize winners
Dutch theoretical physicists
Mars One
People associated with CERN
21st-century Dutch physicists
Recipients of Franklin Medal