Quantum chromodynamics

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 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.

In this interview, David Zierler, Oral Historian for AIP, interviews John Schwarz, Harold Brown Professor of Theoretical Physics, Emeritus, at Caltech. He describes his family background as a childhood of European emigres, both of whom were scientists, and who escaped Nazi persecution at the beginning of World War II. Schwarz recounts his childhood in Rochester and then on Long Island, and he describes his undergraduate experience at Harvard, where he studied mathematics. Schwarz explains how his interests in the “real world” drew him to physics, which he pursued in graduate school at Berkeley and where he worked with Geoffrey Chew on pursuing a theory of the strong nuclear force. He explains Chew’s conclusion that quantum field theory was not relevant toward developing a theory on the strong nuclear force, and he proposed, alternatively, the S-matrix, which in turn was overtaken by the Yang-Mills gauge theory known as quantum chromodynamics. Schwarz explains how Veneziano’s Eular beta function grew out of the S-matrix program, which extended into a new theory called the dual resonance model, which came to be known as string theory because the model was understood as a kind of quantum theory of one-dimensional objects called strings. Schwarz recounts his contributions to these developments during his time at Princeton, where he collaborated with David Gross, André Neveu, and Joël Scherk. He discusses the significance of Claud Lovelace’s work at CERN, where he found that singularities could be made into poles, and he explains how the second string theory came about in 1971 which required ten spacetime dimensions. Schwarz explains why string theory was not part of the work Glashow and Georgi were doing to unify the three forces of electromagnetism, weak interactions, and strong interactions within a larger gauge symmetry. He describes Feynman’s reluctance in accepting QCD but why, in the end, it proved to be the superior way to explain the strong nuclear force. Schwarz describes his decision to join the faculty of Caltech with the encouragement of Gell-Mann, and he explains the ongoing value of string theory even with QCD firmly established, because it gives gauge theory interactions. He recounts the “second revolution” of string theory in 1984 and his work with Michael Green, and he describes the initial optimism that supersymmetry would be discovered with the advent of the LHC. Schwartz describes Ed Witten’s rising stature in the field, and he shares his views on why thousands of people remain captivated by string theory today. He provides a response to the common criticism that string theory is untestable, and he explains the significance of Juan Maldacena’s discovery of the connection between string theory and conformally invariant field theories. At the end of the interview, Schwarz reviews what among the original questions in string theory he feels have been answered, and which remain subjects of inquiry, including his interest in new approaches to quantum gravity.