Quantum chromodynamics

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.

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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.

In this interview, Junko Shigemitsu, Professor Emerita in the Department of Physics at the Ohio State University, surveys the field of lattice gauge theory over the course of her career, and she recounts her childhood moving around the world because her father was a diplomat for Japan’s foreign ministry. She explains the circumstances that led her family back to Japan, and her decision to pursue a degree in physics at Sophia University in Tokyo. Shigemitsu discusses her interest in attending Cornell for graduate school, where she studied under the direction John Kogut. She discusses Ken Wilson’s revolutionary work on renormalization, and her thesis work on QCD. Shigemitsu describes her postdoctoral work at the Institute for Advanced Study at a time when lattice gauge theory was beginning to mature, and she discusses her subsequent postdoctoral position at Brown. She explains that opportunities that led to her faculty position at Ohio State and her subsequent research on QCD at non-zero temperatures. Shigemitsu discusses the international HPQCD collaboration and more recent advances in understanding subatomic particles in partnership with SLAC and KEK in Japan. She places the greatest excitement in finding physics beyond the Standard Model in the period starting in 2009, and she explains the increasing utility of computers as their power has grown over the decades. At the end of the interview, Shigemitsu conveys her excitement that the field will yield new discoveries, perhaps including new physics, and that quantum computing will likely be central to these prospects. 

Interview with Pierre Sikivie, Distinguished Professor of Physics at the University of Florida. Sikivie explains how the social isolation imposed by the pandemic has been beneficial for his research, and he recounts his childhood in Belgium and his family’s experiences during World War II. He discusses his undergraduate work and his natural inclination toward theoretical physics, and the opportunities that led to his graduate work at Yale under the mentorship of Feza Gürsey. Sikivie explains that his initial interests were in elementary particle physics which was the topic of his research on Grand Unification and the E6 group. He describes his postdoctoral research at the University of Maryland where he worked on CP violation, and he explains his decision to pursue his next postdoctoral position at SLAC to work on non-Abelian classical theories. Sikivie explains that his interests in cosmology and astrophysics only developed during his subsequent work at CERN, and the circumstances that led to axion research becoming his academic focal point. He describes his appointment to the faculty at the University of Florida and when he became sure that axions would prove to be a career-long pursuit. He narrates his invention of the axion haloscope and how this research evolved into the ADMX collaboration. Sikivie explains why he was, and remains, optimistic about the centrality of axion research to the discovery of dark matter, and he discusses the import of QCD on axion physics over the past thirty years. At the end, Sikivie surveys some of the challenges working in a field whose promise remains in some way hypothetical but which nonetheless holds promise for fundamental discovery.

In this interview, David Zierler, Oral Historian for AIP, interviews Laurence Yaffe, chair of the department of physics at the University of Washington. Yaffe recounts his childhood in northern California and his early interests in science and the influence of his mother, who was a chemist. He discusses his undergraduate experience at Caltech, where he became absorbed in physics even as he continued in his major in chemistry. Yaffe explains his graduate offer from John Wheeler to pursue a Ph.D. in physics at Princeton. He describes the intellectual benefits of going back and forth between the Institute and the department, and he discusses his relationship with his graduate advisor, David Gross. Yaffe explains why he believes string theory should continue to be pursued, particularly in light of developments related to AdS/CFT duality. He describes his decision to return to Caltech for his postdoctoral research, and he recounts his considerations with competing faculty offers from Caltech and Princeton. Yaffe discusses his early faculty career at Princeton and his work on quark and lepton masses and the large-N limit of QCD or Yang-Mills theory. He describes the events leading to his decision to join the faculty at UW and his ongoing interests in QCD. Yaffe explains the evolution of quantum field theory over the course of his career, and he describes how advances in computers have revolutionized theory. He discusses some of the challenges inherent in the current state of the field, and he discusses his advisory work for the Department of Energy. At the end of the interview, Yaffe reflects on the overall and historic excellence of the department of physics at UW, and he explains why he will remain interested in quantum entanglement for the foreseeable future.

In this interview, David Coward reflects on his time at Stanford University and the formation of SLAC. Coward discusses his time as an undergraduate student at Cornell University. He describes how his desire to study under Pief Panofsky influenced his decision to attend Stanford University for graduate school and how Panofsky later encouraged him to work for SLAC. Additionally, he continually reflects upon the role of Panofsky throughout his life and his leadership in the formation of SLAC. Coward details how his engineering background helped him construct a spectrometer facility at SLAC. He details his various sabbaticals at CERN and reflects upon the different work cultures that existed at different labs. He discusses his contributions to a study on quarks that later earned a Nobel Prize in 1990. Coward Reflects on the development of the Spectrometer Facilities Group and his role in putting the team together. He discusses a paper the group published in 1975 on polarized electron-electron scattering at GeV energies that proved the quark model of the proton. Lastly, Coward discusses his experience living in Palo Alto and the progress made in the area during his time there, such as the installation of bike paths and the undergrounding of power lines.

Interview with Phiala Shanahan, assistant professor of physics in the Center for Theoretical Physics at MIT. Shanahan explains the administrative relationship between the department and the Center, and she recounts her childhood in Adelaide, Australia, her experiences at an all-girls school and the benefits this conferred in nurturing her interest in science. She discusses her concentration in computational physics and the mass of the H-dibaryon at the University of Adelaide and her decision to stay on with her undergraduate advisors, Anthony Thomas and Ross Young, for graduate school. Shanahan describes her interest in the proton radius puzzle as a research entry point for her thesis work and why she was interested in how particle physics can be connected more rigorously to quarks, gluons, and ultimately chemistry. She describes the opportunities leading to her postdoctoral research at MIT and some of the cultural adjustments she had to make coming from Australia. Shanahan discusses her collaboration with Will Detmold and she describes her contributions to the NPL-QCD research project and she discusses her first faculty appointment at William & Mary before returning to MIT where she remains in her current appointment and where she is pursuing work on proton structures and in creating ever-faster algorithms. She describes the potential benefits that would be conferred with the availability of true quantum computing for her field, and she describes some of the difficulties she has faced as a woman in getting recognized for her accomplishments in her field of research. At the end of the interview, she emphasizes why her long-term goal is to bridge nuclear physics and chemistry, and why she wants to keep an open mind about pursuing other areas that are both interesting and offer the opportunity to push forward discovery in foundational ways.

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.