Bryce Seligman DeWitt, professor emeritus in the physics department
of The University of Texas at Austin, died on September 23, 2004.
His career was marked by major contributions to classical and
quantum field theories and in particular to the theory of gravitation.
DeWitt was born Carl Bryce Seligman on January 8, 1923, in Dinuba,
California, the eldest of four boys. His paternal grandfather,
Emil Seligman, left Germany around 1875 at the age of 17, and
emigrated to California, where he and his brother established
a general store in Traver. Emil married Anna Frey, a young woman
who had emigrated from Switzerland at about the same time. They
had eleven children, whom Anna raised in the Methodist church.
In 1921, DeWitt's father, who had become a country doctor, married
the local high school teacher of Latin and mathematics. Her ancestors
were French Huguenots and Scottish Presbyterians. DeWitt was
raised in the Presbyterian Church, and the only Jewish elements
in his early life were the matzos that his grandfather bought
around the time of Passover. DeWitt described his early exposure
to religion as a boy in California in a moving memoir, "God's
Rays," published posthumously in Physics Today.
His grandmother told him that Armageddon would come in the summer
of 1997, and she hounded his grandfather to his deathbed, trying
to make him give up his belief in Darwinian evolution. Looking
back in his memoir, DeWitt came to the conclusion that it was
love that gave Christianity its overwhelming impact, but that
love "needs no religious framework whatever to exert its
power."
DeWitt's mother chafed at her rural surroundings and determined
that her sons would live elsewhere. At the age of 12, DeWitt
entered Middlesex School in Concord, Massachusetts. The headmaster
at Middlesex had initiated a national scholarship program similar
to the one at Harvard, and DeWitt had taken (at his mother's
insistence) the competitive examination in which he earned his
admission.
He graduated from Middlesex at the age of 16 and was admitted
to Harvard and Caltech. He chose Harvard because he had become
passionate about rowing while at Middlesex, and Harvard had "crew." He
eventually stroked the Harvard Varsity. As a physics major, he
was deferred from military service, but he always felt guilty
about it. Upon graduation in 1943, he went to work on the Calutron
at Berkeley, the accelerator used in the Manhattan Project for
the final separation of U235 from U238. (This had been recommended
to him by Robert Oppenheimer when, because DeWitt wanted to get
back to California, he had turned down Oppenheimer's invitation
to join a secret research project in an undisclosed location.)
He spent seven months at the Berkeley branch of the Manhattan
Project and then asked to be released. He reasoned that any bright
youngster could do what he was doing (hard soldering, reading
meters, general gofer work), and he didn’t see that his
physics degree was relevant. In January 1944, he enlisted in
the Navy and became a naval aviator, but World War II ended before
he saw combat.
DeWitt came back to Harvard in January 1946. In 1947, he began
his thesis work under the nominal supervision of Julian Schwinger.
The topic he chose – the quantization of the gravitational
field – became his life's work. In 1949, he began his first
postdoctoral year at the Institute for Advanced Study. When Wolfgang
Pauli, in November of that year, learned what he was working
on, he remained silent for several seconds, alternately nodding
and shaking his head (a well-known Pauli trademark), and then
said, "That is a very important problem. But it will take
somebody really smart!"
In 1950, two major but totally unrelated developments occurred
in his life. First, he became engaged to be married to Cecile
Morette, a young French physicist who was in her second postdoctoral
year at the Institute. Second, at the urging of their father,
he and his three brothers began the legal procedures for changing
their surname to a name from their mother's side of the family.
The younger boys were, or had been, at school in the eastern
U.S., and all had encountered repeated misunderstandings and
false assumptions based solely on their surname – something
that had seldom occurred in California.
From June to December 1950, DeWitt was with Pauli at the ETH
in Zurich, and afterward he went to Bombay to spend a postdoctoral
year at the Tata Institute of Fundamental Research. This sojourn
did not make good professional sense, but it suited his roving
spirit. Unfortunately, it ended in an abrupt and serious illness,
which forced his return to Europe. In May 1951, he and Cecile
were married in Paris, and in July they were in Les Houches where
the famous Ecole d'Ete de Physique Theorique was starting its
first year. This school had been created by Cecile as a penance
for marrying a foreigner, but she also saw it as something potentially
valuable in its own right. It was certainly valuable to DeWitt
who, during the summers he was there, was exposed to a very broad
range of topics in theoretical physics. That the school was also
valuable to others is attested by the fact that at its jubilee
in 2001 it numbered among its past students and lecturers 26
who later became Nobel laureates and two who became Fields medalists.
In September 1951, DeWitt, this time accompanied by Cecile,
returned to the Tata Institute (he being determined to complete
his postdoctoral year). Their eldest daughter was born in Bombay
in April 1952. Three other daughters were born during the following
decade. In the summer of 1952, Cecile was back at Les Houches
while DeWitt was looking for a job in the U.S. His years abroad
had kept him out of the market for academic appointments so he
accepted a job at the nuclear weapons laboratory at Livermore,
where he remained for three and a half years. During his stay
at Livermore, in addition to writing a treatise on The Operator
Formalism in Quantum Perturbation Theory, he became the lab's
expert on (2+1)-dimensional hydrodynamical computations (impelled
by NATO's desire to possess nuclear artillery shells). This expertise
was applied by him years later in computations of the behavior
of colliding black holes and by his students in a variety of
astrophysical problems.
Through the efforts of John Wheeler, who had become aware of
his work on quantum gravity, DeWitt was offered and accepted
the directorship of the Institute of Field Physics at the University
of North Carolina (UNC) in Chapel Hill. His initial title at
UNC was visiting research professor, which enabled him to teach,
or not, as he chose, and to have students. With his very first
student, and with the aid of the book of Jacques Hadamard on
the Cauchy problem, he discovered the basic properties of Green's
functions in curved spacetime. He was also led to the beginnings
of a manifestly covariant quantum theory of gravity in which,
unlike the usual approach to quantum mechanics, the Hamiltonian
has no role to play. In quantum mechanics, the commutator AB-BA
of any two quantities A and B is inferred from a quantity known
as the Poisson bracket, which is calculated on the basis of classical
mechanics. DeWitt came upon the 1952 paper of Rudolf Peierls,
which gave a global definition of the Poisson bracket in terms
of these Green's functions. Peierls' definition yields a completely
unambiguous Poisson bracket for any pair of quantities, whose
definition does not depend on the choice of coordinate system.
The problem now addressed by DeWitt was to extend these classical
results to the quantum theory with all its infinities.
In January 1957, Cecile, who had also been given the title of
visiting research professor, organized the first of the General
Relativity and Gravitation (GRG) conferences: "On the Role
of Gravitation in Physics." The participants included Christian
Møller, Leon Rosenfeld, Andre Lichnerowicz, Hermann Bondi,
Thomas Gold, Dennis Sciama, Peter Bergman, John Wheeler, and
Richard Feynman. Samuel Goudsmit had recently threatened to ban
all papers on gravitation from the Physical Review and Physical
Review Letters because he and most American physicists felt
that gravity research was a waste of time. The conference aimed
to point out the shallowness of this view. In those early years,
arguments were often put forward that gravity should not be quantized.
Feynman vigorously disagreed and himself became interested in
the problem while visiting Chapel Hill. Four years later, at
the GRG conference in Warsaw, Feynman gave the first correct
statement of how to quantize gravity (and also the non-Abelian
gauge field) in the one-loop order of perturbation theory. He
was the inventor of what are known as "ghosts" in non-Abelian
gauge theories. These theories, invented in 1954 by Chen-Ning
Yang and Robert Mills, became the subject of much of DeWitt's
future work and later turned out to furnish the basis of successful
theories of all of the observed interactions of elementary particles
except gravitation.
DeWitt, who had followed Feynman's work closely, extended it
to two-loop order in 1964. In the meantime he had pushed forward
on several other fronts. On three occasions, he had presented
courses of lectures at Les Houches. In 1963, he gave his most
famous course, "The Dynamical Theory of Groups and Fields," which
was published as a book the following year. In it, he introduced
a condensed notation applicable to all field theories, extended
Schwinger's heat kernel methods to curved spacetime and other
non-constant backgrounds, and gave the first (and now standard)
nonperturbative definition of the effective action as a Legendre
transform of the logarithm of the vacuum persistence amplitude.
By the end of 1965, he had found the rules for quantizing the
gravitational and non-Abelian gauge fields to all orders; however,
this work did not get published until late 1967 for two reasons.
First, his Air Force grant was terminated, and he could not pay
the page charges that the Physical Review had begun
levying. Second, there seemed to be no rush. The standard model
of electroweak interactions had not yet been worked out, and
the fundamental importance of the non-Abelian gauge field was
not fully understood. Dimensional regularization, which would
make renormalization easy, had not yet been invented. And, he
was momentarily sidetracked by John Wheeler's eagerness to develop
a canonical approach to quantum gravity based on Dirac's theory
of constraints. The application of Dirac's methods to gravity
had some interesting features of its own. DeWitt was led to what
subsequently became known as the Wheeler-DeWitt equation, which
has since been applied many times to problems in quantum cosmology.
DeWitt's paper on the non-Abelian Feynman rules finally appeared
two weeks before a paper by Fad'deev and Popov deriving the same
rules. These rules were seized upon by 't Hooft and Veltmann
who, apparently unaware of DeWitt's contributions, proceeded
to call Feynman's ghosts "Fad'deev-Popov ghosts," a
name that has stuck.
In the summer of 1968, DeWitt was visited by Max Jammer who
was thinking of writing a book on the interpretation of quantum
mechanics and its history. DeWitt was astonished to learn that
Jammer had never heard of Hugh Everett III, who had published
a paper on this topic in the same issue of the Reviews of
Modern Physics in which contributions from the 1957 Chapel
Hill conference had appeared. In fact, Everett's paper, which
proposed that one should regard the formalism of quantum mechanics
as providing a representation of reality in exactly the same
sense as the formalism of classical mechanics was once thought
to do, had been totally ignored by the physics community during
the intervening years. DeWitt resolved to correct this situation
and, in 1970, wrote a popular article in Physics Today expounding
Everett's views. These views, although almost totally rejected
at first, have little by little gained increasing numbers of
adherents. The assumption that the formalism of quantum mechanics
provides a direct representation of reality implies the existence
of what from the point of view of classical physics would appear
as many "realities." Everett's interpretation consequently
became known as the "many worlds" interpretation. DeWitt,
who found Everett's ideas liberating, in the sense that they
lead one to ask questions that might not occur to one otherwise,
became regarded as one of the foremost champions of the many
worlds interpretation although it was always peripheral to his
main interests.
By 1970, the DeWitts had begun to think of leaving Chapel Hill.
Several years earlier Bryce's title had been changed to professor
while Cecile had been demoted to lecturer. In addition, upon
the death of Agnew Bahnson Jr., the Winston-Salem industrialist
who had founded and provided financial security for the Institute
of Field Physics, and upon his widow's transfer of its backup
funds to the university, the status of the Institute underwent
an abrupt change. No longer was it possible to offer postdoctoral
positions with the assurance that funds would be available even
if grant money failed to materialize. The postdocs of earlier
years had included Felix Pirani, Ryoyu Utiyama, Peter Higgs,
and Heinz Pagels. This stream of talented people had now come
to an end.
In the fall of 1971, DeWitt accepted a visiting professorship
at Stanford. The physics department was looking for a replacement
for Leonard Schiff, who had died the year before. Stanford indeed
looked promising, not least because the mathematics department
expressed an interest in hiring Cecile. The members of the physics
department were sufficiently pleased by Bruce's visit that they
made preparations to offer him a professorship. This, however,
was vetoed by Felix Bloch who, upon learning that Bryce had changed
his surname 20 years earlier, refused to allow the offer to proceed.
An alternative then appeared at The University of Texas at Austin.
A few years earlier, Alfred Schild had secured the University's
agreement to establish a well-funded Center for Relativity. Schild,
as its director, brought to Austin such people as Roy Kerr, Robert
Geroch, and Roger Penrose. In a short time, these gifted young
people were snapped up by other more prestigious institutions.
There was always a vacancy at the Center for Relativity, and
Schild was determined to get the not-so-young DeWitts. He arranged
that they would both be offered full professorships, Cecile half
time at first in the astronomy department and then later full-time
in the physics department.
Mixing astronomy and relativity, the DeWitts became co-leaders
of an NSF-funded eclipse expedition to Mauritania in 1973. The
aim of the expedition was to repeat, with modern technology,
the light-deflection observations of bygone years. This effort
would not have been possible without warm cooperation between
the astronomy department and the Center for Relativity.
The DeWitts were instrumental in attracting to Austin John Wheeler,
who was facing compulsory retirement at Princeton. Texas gave
him a center of his own to which he invited people such as David
Deutsch and Philip Candelas, with whom DeWitt had become acquainted
during a Guggenheim year as visiting fellow at All Souls College,
Oxford, in 1975-76.
DeWitt's early years at Texas were devoted to the colliding
black hole problem and to the problems of quantum field theory
in curved spacetime, including the problem of the conformal or
Weyl anomaly and the description of Hawking radiation. He also
continued to develop his Hamiltonian-free approach to quantum
field theory. By 1983, when he again lectured at Les Houches,
he was able to set the theory of conservation laws, tree theorems,
and dimensional and zeta-function regularizations completely
within this framework.
In the late 1980s, he wrote his book, Supermanifolds.
Supermanifolds are spaces that have coordinates that anticommute
(in the sense that xy=-yx) as well as having the ordinary sort
of commuting coordinates (for which xy=yx). The book brought
together in a systematic way a number of related but never-before
united topics, such as supertraces, superdeterminants, Berezin
integration, super Lie groups, and path-integral derivation of
index theorems. A useful topology that he introduced for integration
on supermanifolds is now known by mathematicians as the DeWitt
topology. A second edition of Supermanifolds appeared
in 1991.
In 1992, he and his associates completed a lattice quantum field
theory study of the O(1,2) nonlinear sigma model in four dimensions.
This model, which bears some similarities to quantum gravity,
proved to be trivial in the continuum limit.
His last book, The Global Approach to Quantum Field Theory (1042
pages), was published in 2003, when he was 80 years old. It effectively
sets forth his special viewpoint on theoretical physics and includes
the following unique contents:
- A derivation of the Feynman functional integral from the
Schwinger variational principle and a derivation of the latter
from the Peierls bracket.
- Proofs of the classical and quantum tree theorems.
- A careful statement of the many worlds interpretation of
quantum mechanics in the context of both measurement theory
and the localization-decoherence of macroscopic systems, which
leads to the emergence of the classical world.
- A display of the many roles of the measure functional in
the Feynman integral, from its relation to the VanVleck-Morette
determinant in semiclassical approximations, to its justification
of the Wick rotation procedure in renormalization theory.
- Repeated use of the heat kernel in a wide variety of contexts,
including a zeta-function computation of the chiral anomaly
in curved spacetime.
- An exhaustive analysis of linear systems, both bosonic and
fermionic, and their behavior as described through Bogoliubov
coefficients.
- A novel approach to ghosts in non-Abelian gauge theories.
Use of the Vilkovisky connection to eliminate the
ghosts in the closed-time-path formalism that is used to calculate "in-in" expectation
values.
- A proof of the integrability of the Batalin-Vilkovisky "master" equation.
DeWitt's obituary in
Physics Today notes,
As a scientist, Bryce was bold and extraordinarily clear thinking. He eschewed bandwagons and the common trend of trying to maximize one's publication list. Most of his papers are long masterpieces of thought and exposition. Indeed, Bryce had a rare, perfect combination of physical and mathematical intuition and raw intellectual power that was very rarely surpassed.
To this, we would add that he was a fount of wisdom about theoretical physics for his colleagues at The University of Texas. His death has left a gap in our working lives that time does not seem to cure.
For his many contributions to physics, DeWitt received the Dirac Medal of the Abdus Salam International Centre for Theoretical Physics (Trieste), the Pomeranchuk Prize of the Institute of Theoretical and Experimental Physics (Moscow), and the Marcel Grossmann Prize with Cecile. Shortly before his death, he was named the recipient of the American Physical Society's Einstein Prize for 2005. He was a member of the National Academy of Sciences and the American Academy of Arts and Sciences. DeWitt was an indefatigable trekker and mountain climber, traveled widely, and lectured in many parts of the world. He is survived by his wife, Cecile, and four daughters.
<signed>
William Powers Jr., President
The University of Texas at Austin
<signed>
Sue Alexander Greninger, Secretary
The General Faculty
This memorial resolution was prepared by a special committee consisting of
Steven Weinberg (chair), Austin M. Gleeson, and Richard A. Matzner.
