Quantum field theory

Interview with Robert M. Wald, Charles H. Swift Distinguished Service Professor of Physics at the University of Chicago, where he also has appointments with the Kadanoff Center and the Kavli Institute for Cosmological Physics. Wald recounts his childhood in New York, he describes the tragedy of losing his parents in an airplane crash when he very young, and he explains the ongoing legacy of his father Abraham Wald who was a prominent professor of statistics at Columbia. He describes his high school education at Stuyvesant and his decision to pursue a physics degree at Columbia, where he became close with Alan Sachs, who supervised him at Nevis Laboratory. Wald explains his decision to focus on general relativity for graduate school and his interest in working with John Wheeler at Princeton. He describes the excitement surrounding recent advances in approaching astrophysics through relativity, the significance of the discovery of pulsars and the field of black hole uniqueness, and he discusses his postdoctoral research with Charles Misner at the University of Maryland. Wald describes the impact of Saul Teukolsky’s discovery of a variable Weyl tensor component that satisfied a decoupled equation, and he explains the circumstances leading to his faculty position at Chicago, where he was motivated to work with Bob Geroch. He reflects on the experience writing Space, Time, and Gravity, the advances in black hole collapse research, and he explains why he felt the field needed another textbook which motivated him to write General Relativity. Wald discusses his work on the Hawking Effect and his long-term interest in quantum field theory, and he explains the influence of Chandrasekhar on his research. He describes his contributions to the LIGO collaboration, and he explains what is significant about the Event Horizon Telescope’s ability to capture an image of a black hole. Wald explains the state of gravitational radiation research and the accelerating universe, he prognosticates on what advances might allow for a unification of gravity and the Standard Model, and he explains why dark energy is apparently a cosmological constant. At the end of the interview, Wald discusses his recent work on the gravitational memory effect and, looking to the future, he explains his interest to continue working to understand the S-matrix in quantum electrodynamics.

Interview with Juan Maldacena, Carl P. Feinberg Professor at the Institute for Advanced Study. Maldacena recounts his childhood in Buenos Aires, he discusses his undergraduate education at the University of Buenos Aires and his advanced work in physics at Instituto Balseiro where he had his initial exposure to string theory. He explains his decision to pursue a graduate degree at Princeton where he worked with Curt Callan and where he benefited from Ed Witten’s lectures on dualities in quantum field theory and in string theory. Maldacena describes his thesis research on conformal field theories with boundaries and the significance of Joe Polchinski’s discovery of D-branes, and he conveys the importance of his collaboration with Andy Strominger as a postdoctoral researcher at Rutgers. He describes his paper on AdS/CFT while at Harvard and he explains his work on non-gaussianities and his realization that string theory would be useful for cosmology. Maldacena explains his decision to leave the faculty at Harvard to join the Institute, and he describes his subsequent research on space-time and entanglement, the chaos of black holes and the likelihood that they are rapidly thermalizing systems. He explains the contributions of string theory research as offering physics a model for quantum gravity and for the quantum mechanics of spacetime itself, and he shares his perspective on broader debates about how many researchers should or should not be involved in string theory work. At the end of the interview, Maldacena describes his hope in the future to better understand the interiors of black holes.

Interview with David Griffiths, Professor Emeritus of Physics at Reed College. Griffiths discusses his current projects on Sidney Coleman’s lecture series and a completing a fifth edition of his textbook on electrodynamics. He surveys the current interplay between experiment in theory in today’s world of particle physics, and he reflects on his career rooted in small teaching colleges, as opposed to pursuing an alternate path at large research universities. Griffiths recounts his childhood in Berkeley and then in Madison in support of his father’s academic career, and he describes finishing out high school in Vermont before attending Harvard. He laments the poor physics education Harvard offered when he was an undergraduate, and he explains his decision to remain at Harvard for graduate school, where Sidney Coleman and Carl Bender advised his thesis work on massless field theory. Griffiths discusses his postdoctoral appoints at the University of Utah and then the University of Massachusetts, and he explains how the November revolution at SLAC resonated with him. After brief teaching appointments at Mount Holyoke and Trinity Colleges, Griffiths explains his decision to join the faculty at Reed and how he learned to strike the right balance between teaching and research. He describes the origins and his motivations in writing textbooks for physics students and how he has integrated pedagogy into his mentorship of students. Griffiths discusses the influence of Kuhn in his more recent survey of physics in the twentieth century, and at the end of the interview, he explains why including students in his own research is both personally and academically meaningful.

In this interview, David Zierler, Oral Historian for AIP, interviews Cumrun Vafa, Hollis Professor of Mathematicks and Natural Philosophy in the Department of Physics at Harvard. Vafa surveys the current state of the field in string theory, and he recounts his upbringing in Iran and his family’s goal for him to pursue education in the United States. He explains the opportunities that led to his acceptance to MIT, and his intellectual journey from being practical-minded in his study of economics and engineering, to his blossoming love for mathematics and physics. Vafa describes his early difficulties reconciling the formalism of math with the intuition he sensed pervaded concepts in physics, and he explains how this changed as a student of Ed Witten’s at Princeton. He describes his entrée into string theory at the time that Witten had committed himself to learning string theory, and he describes the evolution of the field from the first to the second “revolutions” from 1984 to 1994. Vafa describes his time as a junior fellow at Harvard and some of the tensions that existed in the physics department between senior faculty who were not interested in string theory, and the junior faculty who were. He explains the circumstances that led to his rapid tenure at Harvard and he describes the ideas that became his “Swampland” concept. Vafa discusses his collaborations with Andy Strominger on black holes and with Robert Brandenberger on string gas cosmology and his solo research on F-theory. He talks about the long-term prospects for a truer understanding of quantum gravity, and at the end of the interview, Vafa engages with critics and string theory, and delineates between those who are not interests themselves (which he understands and respects) and those who wish to make it more difficult for others to study string theory (which he finds problematic). Vafa acknowledges the current gap between string theory and experimental verification but asserts that this gap is a function of current technological limitations in observation, and not a shortcoming of string theory itself.

Interview with Stephen Wolfram, Founder and CEO of Wolfram Research. He describes his recent efforts to launch an “assault” on the final theory of physics and he muses on the possibility that the human mind is a quantum mechanical system. Wolfram recounts his family’s German-Jewish heritage and his upbringing in Oxford, where his mother was an academic. He describes his schooling which put him on a trajectory to skip grades and begin college at age fifteen and to complete his PhD at age twenty. Wolfram discusses his early interests in particle theory and computer systems and he describes his summer research visit to Argonne Lab and his visit with David Gross at Princeton. He explains the circumstances that led to his admission at Caltech to work on QCD and his decision to accept a faculty appointment at Caltech thereafter. Wolfram narrates the origins of the SMP program and the intellectual property issues he experienced as a Caltech professor. He explains his intellectual migration away from physics toward the work that would become Mathematica and Wolfram Language, and he describes his time at the Institute for Advanced Study. Wolfram discusses the business model he adopted for Mathematica and his educational motivations that were incorporated into the program from its inception. He discusses his interests in complex system research and his fascination with cellular automata, and he narrates the intellectual process that led to his book A New Kind of Science. Wolfram surveys the reviews, positive and negative, that he has received for this work, and he offers a retrospective look at how NKS has held up as it approaches its twentieth anniversary. He describes the launch of Wolfram Alpha and the promises and limits of quantum computing and why he has returned to physics in recent years. At the end of the interview, Wolfram asserts that he has never taken risk in any of his decisions, and he considers how his approach and the intellectual and business ventures he has pursued will continue to yield solutions for many of the ongoing and seemingly intractable problems in physics.

Interview with Lee Smolin, Founding and Senior Faculty Member at the Perimeter Institute with faculty appointments at the University of Toronto and the University of Waterloo. Smolin narrates the origins of the Perimeter Institute and he describes his unorthodox views on what exactly cosmology is. He describes loop quantum gravity and the notion of a “theory of everything” and why he has much love for string theory despite perceptions of the opposite. Smolin explains the utility and trappings of the Standard Model and he searches for deeper meaning in the origins and societal impact of the pandemic. He recounts his childhood in Cincinnati and his early appreciation for physics and the circumstances that led to his undergraduate education at Hampshire. Smolin explains his attraction in working with Sidney Coleman at Harvard, and why he saw a grand plan in his desire to learn quantum field theory. He describes meeting Abhay Ashtekar and his postdoctoral work at UC Santa Barbara and then at the Institute for Advanced Study. Smolin describes his formative relationship with Chandrasekhar at Chicago, his first faculty appointment at Yale, and his tenure at Syracuse where he found a strong group in relativity and quantum gravity. He explains his reasons for transferring to Penn State and his involvement in loop quantum gravity achieving a mature state amid a rapidly expanding “relativity community” throughout academic physics. He describes his time at Imperial College, where he developed a quantum gravity center with Chris Isham and he historicizes the technical developments that connected his theoretical work with observation. Smolin describes his book "The Life of the Cosmos" and his foray into thinking about biology and why he identifies as a self-conscious Leibnizian who tries to connect cosmology with the concept of a god and the centrality of astrobiology to these issues. At the end of the interview, Smolin explains why he continually returns to quantum gravity, and he conveys his interest in keeping philosophy at the forefront of his research agenda.

In this interview, David Zierler, Oral Historian for AIP, interviews James (BJ) Bjorken, Professor Emeritus of Particle Physics and Astrophysics at SLAC. Bjorken recounts his childhood in Chicago and he explains how parents’ conservative worldview influenced his decision to attend MIT and not the more liberal and nearby University of Chicago for college. He describes the formative influence of Professor Hans Mueller and the fatherly role that Sid Drell played for him, and he discusses his work on the 300 MeV electron synchrotron lab under the direction of Al Wattenberg and Bernie Feld. Bjorken explains his decision to pursue a graduate degree in physics at Stanford, which he remembers as part of a “western exodus” from Harvard, and he describes the origins of the rift between the physics faculty and the “new guard” who supported and created SLAC under Pief Panofsky’s direction. He explains the intellectual tradition from Vicki Weiskopf to Sid Drell and Burt Richter that informed the development of his dissertation analyzing the properties of scattering amplitudes, and he discusses the faculty’s interest in keeping him at Stanford as a postdoc. He describes his early visits to CERN and to the Soviet Union, and he conveys how impressed he was with the level of physics research in Moscow. Bjorken discusses his early work on creating a robust experimental research agenda at SLAC and he reflects on the significance of the “November Revolution” of 1974 and why quark and gluon confinement was of fundamental importance. He explains his decision to move to Fermilab in 1979 to do neutrino experiments and the E137 axion search project, and he contextualizes the major debates in the 1980s about the future of high energy physics. Bjorken recounts his introduction to the internet over the course of the Minimax project, and he explains the freedom he feels in retirement to conduct research that can be simultaneously ambitious and likely to lead nowhere. He explains his contributions to understanding dark energy and the Kasner metric, and at the end of the interview, Bjorken explains the satisfaction of spending a career that spans from the era before the Standard Model to the present, and how the golden age in physics currently has passed from particle physics to astrophysics and cosmology.

In this interview, David Zierler, Oral Historian for AIP, interviews Raymond Sawyer, professor of physics emeritus at the University of California at Santa Barbara.  Sawyer recounts his childhood growing up in many towns in the Midwest as a function of his father’s frequent job transfers. He discusses his undergraduate studies at Swarthmore College, where he developed his interest in physics, and he explains the atmosphere of wide career opportunity in the age of Sputnik. Sawyer describes his graduate research at Harvard, where he worked in Norman Ramsey’s molecular beam lab.  He explains how Julian Schwinger came to be his advisor and he describes his dissertation study on symmetries and the weak interactions of elementary particles. Sawyer discusses his postdoctoral research at CERN where he joined the theory group and where he studied the decay of a charged pion. He describes his second postdoctoral appointment at the University of Wisconsin and his work in quantum field theory at the Institute for Advanced Study which he did at the invitation of Robert Oppenheimer.  Sawyer explains the series of events leading to his decision to join the faculty at UC Santa Barbara, and he discusses his role in the formation of the Institute for Theoretical Physics. He explains his invention of charged pion condensation and he describes his work in university administration. At the end of the interview, Sawyer reflects on his contributions throughout his career, and he explains how he has kept active in the field during retirement.

In this interview, David Zierler, Oral Historian for AIP, interviews John Galayda, Project Director for the NSTXU project at Princeton Plasma Physics Laboratory. Galayda recounts his childhood in New Jersey and his undergraduate experience at Lehigh University. He discusses his research work as a graduate student at Rutgers, where he was interested in applying accelerator physics to energy supply solutions, and where he focused on quantum field theory. Galayda discusses his research at Brookhaven he worked on the NSLS and the Transverse Optical Klystron. He explains his decision to move to Argonne where he conducted research on X-ray beams, and he describes the factors that convinced him to join SLAC in 2001. Galayda describes SLAC’s interest in building a next-generation Linear Collider. He explains some of the major research questions that propelled the LCLS and he describes the recruitment process that led to his current work at PPPL. In the last portion of the interview, Galayda surmises on the future of plasma physics and he emphasizes the importance of working with good people.

In this interview, Klaus Hasselmann discusses topics such as: his family background and how he became interested in physics; getting his PhD from the Max Planck Institute for Fluid Dynamics and Gottingen University; Walter Tollmien; University of California, San Diego Institute for Geophysics and Planetary Physics; Scripps Institute of Oceanography; Walter Munk; Norman Barber; John Miles; Hugh Bradner; George Backus; Klaus Wyrtki; Carl Eckart; Charles David Keeling; researching storms in the south pacific including Hawaii; Frank Snodgrass; Gordon Groves; measuring waves in the North Sea; becoming director of the newly formed Department of Theoretical Geophysics at the University of Hamburg; Donald Menzel; the Max Planck Institute for Meteorology; North Atlantic Treaty Organization (NATO); Woods Hole Oceanographic Institution; Wolfgang Sell; Art Maxwell; Dirk Olbers; Heinz-Hermann Essen; Peter Muller; wave dynamics; Global Atmospheric Research Programme (GARP); Reimar Lust; Kirk Bryan; World Climate Research Programme; European Centre for Medium Range Weather Forecasts (ECMWF); Lennart Bengtsson; El Nino predictions; Intergovernmental Panel on Climate Change (IPCC); carbon dioxide emissions; Hans Hinzpeter; plasma physics; quantum field theory.