Renormalization (Physics)

In this interview, David Zierler, Oral Historian for AIP, interviews Thomas Appelquist, Eugene Higgins Professor of Physics at Yale University. Appelquist recounts his upbringing in rural Iowa and then Indiana, where he attended Catholic high school. He describes his undergraduate experience at Illinois Benedictine College and explains his attraction to attend a small school for college. Appelquist discusses his decision to attend Cornell for his PhD, and recalls that, relative to others in his cohort who went to larger schools, he had the most catching up to do in quantum mechanics. He explains the development of his thesis topic under the direction of Don Yennie, which focused on aspects of renormalization theory using the Feynman parametric approach. Appelquist contextualizes some of the broader questions in quantum field theory and quantum electrodynamics at this time, and he describes the opportunities that led him to SLAC for his postdoctoral research. He describes his interests there as focused on theories of the weak interactions, and he describes his initial faculty appointment at Harvard where he joined the particle theory group led by Shelly Glashow and Sidney Coleman. Appelquist discusses his close collaboration with Helen Quinn on how to renormalize Yang-Mills theories, and he explains his decision to take a tenured position at Yale in consideration of the culture at Harvard, where the prospects of tenure were minimal. He describes the revolutionary discoveries of asymptotic freedom, QCD, and the “November Revolution” at SLAC and Brookhaven at the time. Appelquist describes his research and administrative activities to advance the particle theory group at Yale, and his overall efforts to improve the department as chair and in particular building up the condensed matter theory group. He discusses his tenure as Dean of the Graduate School and his long-term involvement with the Aspen Center. At the end of the interview, Appelquist describes his current interests in lattice gauge theory and explains why he expects that physics will see double beta decay in the next generation of experiments.

Interview with Arthur Jaffe, the Landon Clay Professor of Mathematics and Theoretical Science at Harvard University. Jaffe discusses his childhood in New York, where his father was a physician. He shares memories of life during World War II and his affinity for building model airplanes and radios. Jaffe recalls the factors that led him to pursue his undergraduate degree at Princeton, where he began as a chemistry major but switched to physics. He recounts how he learned about the work of Arthur Wightman, leading him to continue at Princeton for his graduate studies. Jaffe describes his work on bosonic field theories and his time at a summer program in Montenegro. He discusses his move to Stanford and his work in the theory group at SLAC under Sidney Drell. Jaffe recalls the beginnings of his collaboration with James Glimm, as well as his move to Harvard. He explains his role in forming the Clay Mathematics Institute at Harvard and discusses his involvement in the International Association of Mathematical Physics and the American Mathematical Society. Jaffe shares his take on topics such as superstring theory, supersymmetry, and the four-dimensional problem, and reflects more broadly on changes he has seen in the field of mathematics over the years. 

Interview with David Gross, Chancellor’s Chair Professor of Physics at University of California in Santa Barbara and a permanent member of the Kavli Institute of Theoretical Physics (KITP). Gross begins by describing his childhood in Arlington, Virginia and his family’s later move to Israel. This led to his decision to enroll at the Hebrew University of Jerusalem for his undergraduate studies in physics and mathematics. Gross recalls his acceptance at Berkeley for his graduate studies, where Geoffrey Chew became his advisor. He explains his early interests in strong interactions, quantum field theory, and S-matrix theory. Gross then describes taking a fellowship at Harvard after completing his PhD, where he recalls his early involvement in string theory. He speaks about his subsequent move to join the faculty at Princeton, as well as his introduction to Frank Wilczek, one of his first graduate students with whom he later shared the Nobel Prize. Gross takes us through the discovery of asymptotic freedom, the development of quantum chromodynamics, and the impact these had on the Standard Model. He discusses his decision to leave Princeton for UCSB, where he focused on growing the KITP and securing funding. Gross describes how his research interests have shifted over the years across topics such as confinement, quantum gravity, and more recently back to string theory. Toward the end of the interview, Gross speaks about his work to develop institutes similar to KITP in other countries, as well as his term as President of the American Physical Society in 2019.

Interview with William Marciano, Senior Physicist at Brookhaven National Laboratory. Marciano recounts his upbringing in Brooklyn and his early interests in science, and he describes his undergraduate work at RPI and then NYU. He explains his decision to remain at NYU for his graduate research to study under the direction of Alberto Sirlin, and his thesis research on dimensional regularization. Marciano discusses his postdoctoral appointment at Rockefeller University where he worked on the SU(5) model of Grand Unification, and the opportunities that led to his promotion there to a faculty position. He explains his short tenure at Northwestern before joining Brookhaven, where kaon physics was taking center stage, and where ISABELLE was being built. Marciano discusses the origins of the Lab's g-2 experiment, and he compares the demise of ISABELLE to that of the SSC, for which he served on the program advisory committee. He describes the success of RHIC, and he discusses his research focus on muon and neutrino physics for the Lab's AGS program. Marciano explains his proposal that led to DUNE at Fermilab and he surveys his long record of advisory work for the HEPAP community and how the United States has contributed to the LHC. He reflects on winning the Sakurai prize and his contributions in establishing the validity of the Standard Model at the level of its quantum corrections. Marciano describes his recent work in dark physics, and he surveys the current state of play in muon physics and the Intensity Frontier. At the end of the interview, Marciano compares the diffuse network of the U.S. National Lab system to the centrality of CERN in Europe, and he explains why his work on DUNE and CP violation has been so personally meaningful.

Interview with Toichiro Kinoshita, a Japanese-born physicist who is best known for pioneering the value of muon g-2, the anomalous magnetic moment of the muon. Kinoshita describes his education—Daiichi High School, Tokyo University—how he avoided military service during World War II, and meeting and marrying his wife, Masako Matsuoka. He describes his introduction to quantum electrodynamics and renormalization through papers by Dyson and Feynman. His early research also involved work on the C-meson theory developed by Sakata. After the war, Kinoshita came to the United States to the Institute for Advanced Study, then as a postdoc at Columbia in 1954. In 1955 Kinoshita moved to Cornell. He became particularly interested in making calculations to test the theory of quantum electrodynamics. He describes his introduction to computers at Princeton, using von Neumann’s computer. The interview covers how he became interested in calculating g-2 at CERN in 1966, and his subsequent efforts, the first being the sixth order calculation, where the light-by-light diagram enters for the first time. He describes his efforts doing the eighth order calculation, and his collaboration with Makiko Nio, as well as his calculations of the tenth order. Physicists whom he describes more than briefly include Kodaira, Tomonaga, Nambu, and Nio. Near the end, Kinoshita describes the importance of g-2 experiments, and his recent work. 

Interview with Peter Lepage, Tisch Family Distinguished University Professor of Physics at Cornell. He recounts his childhood in Montreal and his decision to pursue an undergraduate degree in physics at McGill. Lepage discusses his Master’s work at Cambridge University and his decision to do his thesis research in particle physics at Stanford. He describes the fundamental advances happening at SLAC during his graduate years and his work on bound states of electrons and muons under the direction of Stanley Brodsky. Lepage discusses his postdoctoral appointment at Cornell and his work in high-precision QED calculations in atoms, and he describes the foundational impact of Ken Wilson’s work on lattice QCD and the intellectual revolution of renormalization. He describes this period as his entrée into QCD research, and he emphasizes the beauty of Ithaca and the supportive culture of the Physics Department as his main reasons to accept a faculty position at Cornell. Lepage explains how and when computers became central to Lattice QCD research and why effective field theory was an area of specialization that was broadly useful in other subfields. He describes the ongoing stubbornness of the Standard Model, and he discusses his tenure as chair of the department, then as Dean of the College of Arts and Sciences, and his work on PCAST in the Obama administration. Lepage explains his longstanding interest in physics pedagogy, and he discusses his current work on the numerical integration program called VEGAS. In the last part of the interview, Lepage emphasizes that the most fundamental advances in physics are in astrophysics and cosmology and that lattice QCD should be “kept alive” because it’s unclear where it is going until physics goes beyond the Standard Model.

Interview with Michael Kosterlitz, Harrison E. Farnsworth Professor of Physics at Brown University. He recounts his family background in Germany and his upbringing in Aberdeen, Scotland, and he explains that opportunities that led to his undergraduate admission at Cambridge University where he developed his life-long passion for rock climbing. He describes his early interest in high-energy physics and his decision to pursue a graduate degree at Oxford where he worked on the Veneziano and dual resonance models under the direction of John Taylor. Kosterlitz discusses his postdoctoral work first in Torino and then at Birmingham where he met David Thouless and where he developed his initial interest in condensed matter and his subsequent expertise in phase transitions and superfluidity. He explains the revolutionary advances of Ken Wilson’s renormalization group and his decision to go Cornell where he enjoyed a foundational collaboration with David Nelson and Michael Fisher on crossover problems in critical phenomena. Kosterlitz discusses his decision to join the faculty at Brown, and he provides an overview in the advances in superfluidity in the 1970s and 1980s. He discusses the research that was eventually recognized by the Nobel prize committee and the experiments that bore out the theoretical predictions which were an essential prerequisite to the award. Kosterlitz describes the many benefits conferred as a result of winning the Nobel, and he provides perspective on how he has coped with his diagnosis of multiple sclerosis over the years. At the end of the interview, Kosterlitz explains his reluctance to prognosticate on future trends in the field because his experiences have proved to him that one can never know such things and that research breakthroughs are often unforeseen.

Interview with Gerard 't Hooft, University Professor of Physics (Emeritus) at Utrecht University in the Netherlands. 't Hooft considers the possibility that the g-2 muon anomaly experiment at Fermilab is suggestive of new physics, and he reflects broadly on the current shortcomings in our understanding of quantum mechanics and general relativity. 't Hooft recounts his childhood in postwar Holland and the influence of his great uncle, the Nobel Prize winner Frits Zernike and his uncle, the theoretical physicist Nico van Kampen. He describes his undergraduate education at Utrecht University where he got to know Martinus Veltman, with whom he would pursue a graduate degree and ultimately share the Nobel Prize. 't Hooft explains the origins of what would become the Standard Model and the significance of Yang-Mills fields and Ken Wilson’s theory of renormalization. He describes Veltman’s pioneering use of computers to calculate algebraic manipulations and why questions of scaling were able to be raised for the first time. 't Hooft discusses his postdoctoral appointment at CERN, his ideas about grouping Feynman diagrams together, and how he became involved in quantum gravity research and Bose condensation. He explains the value in studying instantons for broader questions in QCD, the significance of Hawking’s work on the black hole information paradox, the holographic principle, and why he has diverged with string theorists. 't Hooft describes being present at the start of supersymmetry, and the growing “buzz” that culminated in winning the Nobel Prize. He describes his overall interest in the past twenty years in thinking more deeply about quantum mechanics and he places the foundational disagreement between Einstein and Bohr in historical context. At the end of the interview, 't Hooft surveys the limitations that prevent us from understanding how to merge quantum mechanics and general relativity and why this will require an understanding of how to relate the set of all integer numbers to phenomena of the universe.

Interview with Michael Creutz, Senior Physicist Emeritus at Brookhaven National Laboratory. Creutz surveys where lattice gauge theory is “stuck” and where there are promises for breakthroughs in the field. He recounts his birthplace in Los Alamos, where his father was a physicist, and his upbringing in Pittsburgh and then San Diego. Creutz describes his undergraduate education at Caltech and his graduate research at Stanford, where Sid Drell supervised his work on deep inelastic scattering. He explains his decision to take a postdoctoral position at the University of Maryland, and he discusses becoming involved in lattice gauge theory following his exposure to Ken Wilson’s work on renormalization. Creutz describes Brookhaven’s focus on proton scattering when he joined the Lab, and he explains his work during the discovery of the J/psi. He explains his motivation for writing a textbook on lattices, and the value of ever-more powerful computers for lattice gauge research. Creutz explains his “controversial” approach to staggered fermions, and his work on topology in lattice theory. At the end of the interview, Creutz discusses his current interests in chiral symmetry, he reflects on the burst of intellectual activity at the dawn of lattice gauge theory, and he explains why parity violation in neutrinos continues to confound theorists.

Interview with Stanley Brodsky, Professor Emeritus at SLAC. Brodsky surveys his current projects after his retirement last year following 54 years of service to SLAC; they include new initiatives on hadron physics and his interest in the muon G-2 experiment at Fermilab. He recounts his upbringing in St. Paul, his early interests in electrical engineering, and his decision to stay close to home and attend the University of Minnesota for his undergraduate education. He explains his decision to remain at Minnesota for his thesis research, where he worked under the supervision of Donald Yennie on computing atomic levels from first principles in quantum electrodynamics. Brodsky describes his postdoctoral appointment at Columbia, where he worked with Sam Ting at DESY computing the QED radiative corrections for Bethe-Heitler pair production. He recalls his original contact with Sid Drell and his decision to come to SLAC to join the theory group in support of the many experimental programs in train, and he recounts the November Revolution and Sam Ting’s visits to SLAC. Brodsky describes some of the key differences in East Coast and West Coast physics in the 1970s, and he discusses his collaboration with Peter Lepage at the beginning of QCD’s development. He highlights the importance of thinking beyond conventional wisdom and he references his work on intrinsic heavy quarks to illustrate the point. Brodksy discusses his research on the Higgs VEV and the long range value of the Brodsky-Lepage-Mackenzie procedure, and he reflects on the many surprises in QCD color confinement that he has encountered. He explains the value of supersymmetry in his research and he considers why it has not been seen yet and why Maldacena’s work on AdS/CFT has been revolutionary. Brodsky describes SLAC’s increasing involvement in astrophysics and how he has managed his research agenda by working on many different projects at the same time. At the end of the interview, Brodsky emphasizes the significance of Bjorken scaling, he historicizes the first work in physics that explored beyond the Standard Model, and he reflects on the importance that luck has played in his career, simply by finding himself, at so many junctures, in being at the right place at the right time.