Cosmology

n this interview, Stephon Alexander discusses current research into quantum gravity and possible extensions to string theory; work to merge quantum mechanics and general relativity; research into the connection between music and cognitive science; experience as a jazz musician; intersections of philosophy and physics; experience as president of the National Society of Black Physicists (NSBP); challenges and stigmas associated with being a Black academic; growing up in both rural Trinidad and the Bronx; undergraduate experience at Haverford; graduate work at Brown; guidance from Robert Brandenberger into the field of quantum gravity, applying particle physics to astrophysics and cosmology; thesis research on solitons and topological defects and its role in string cosmology and theory; decision to take postdoc at Imperial College London focusing on M-theory and integrating string theory with cosmic inflation; influence of Alan Guth; work on D-brane driven inflation; experience in the underground London music scene; decision to go to SLAC in Stanford and work under Michael Peskin; loop quantum gravity; time as faculty at Penn State; the role and responsibility of the Black academic; recruitment by Brown University; intellectual influence of David Finkelstein; the process of becoming president of NSBP. Toward the end of the interview, Alexander reflects on his books, The Jazz of Physics and Fear of a Black Universe; being an outsider in the field of physics; and revisits his current work on quantum gravity. He emphasizes the importance of in-person collaboration and improvisation. 

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.

Interview with Marc Kamionkowski, William R. Kenan, Jr. Professor of Physics and Astronomy at Johns Hopkins University. He discusses his family heritage of Ashkenazi Jews who left Eastern Europe for Argentina, and his father’s medical research which took the family to Cleveland. Kamionkowski recounts his childhood in Shaker Heights, and he describes his undergraduate work at Washington University, where he switched from pre-med to physics to work with Marty Israel and Joe Klarmann. Despite his lack of preparation, Kamionkowski explains his admission to the University of Chicago, and he describes “the bug” that made him focus on physics and drive to succeed in quantum mechanics and understand quantum field theory. He discusses his thesis research under the direction of Michael Turner on energetic neutrinos from WIMP annihilation in the sun. Kamionkowski discusses his post-doctoral research at the Institute for Advanced Study where he was in Frank Wilczek’s particle theory group. He describes his first faculty appointment at Columbia and how experimental advances had opened up opportunities in cosmology. He explains his decision to move to Caltech because of its strength in theoretical astrophysics and where he became director of the Moore Center. Kamionkowski discusses his subsequent move to Johns Hopkins, and he surveys his recent projects on the Hubble Tension and early dark energy. At the end of the interview, Kamionkowski explains why he has always valued research that bridges the divide between theory and experimentation and why he expects this will continue to inform his broad research agenda.

In this interview, Glennys Farrar, professor at New York University, discusses her career and shifting interests within physics. She details her time as an undergraduate student at University of California, Berkeley. Farrar discusses how she chose to attend Princeton University for graduate school to further her interest in particle theory. She discusses her thesis research which calculated the rate of decay for The Lambda under the mentorship of her advisor Sam Treiman. She describes the social isolation she faced within the physics department as the only woman. Farrar discusses her time as a postdoc at Caltech and details her research on the pion decay constant, as well as pioneering the field of phenomenological supersymmetry. Additionally, she speaks on the sexism she experienced while at Caltech. She details her experience at Rutgers University where she worked on Hadron Physics. Farrar discusses her time at New York University as Chair of the Department of Physics and her efforts putting together a strong faculty. She also details her growing interest in cosmology at this time and describes founding the Center for Cosmology and Particle Physics. She also speaks about her work on the stellar tidal disruption phenomenon. Lastly, Farrar notes her excitement for the increase in computation power in the future and reflects on the merging of different fields of physics.

Interview with Raman Sundrum, distinguished university professor of physics at the University of Maryland. Sundrum recounts his childhood in India, Maryland, and Australia and he describes his life as the child of an international economist with the UN and the World Bank, and a pediatrician. He describes his undergraduate experience at Sydney University where he majored in physics and where he learned that his abilities were in theory. Sundrum discusses his time as a graduate student at Yale, where he was accepted to the math department, and he explains how he immediately shifted over to physics. He explains his initial difficulty settling on a research focus under the direction of Laurence Krauss before he developed a relationship with Mark Soldate and settled on thesis research on particle theory beyond the Standard Model. Sundrum discusses his postdoctoral work at Berkeley, where he spent time at the Lawrence Berkeley Laboratory. He describes being recruited by Howard Georgi to do postdoctoral work at Harvard, and he explains how he collaborated with Lisa Randall and how the Randall-Sundrum papers originated. Sundrum describes the impact of this collaboration on research in supersymmetry, and he explains the events leading to his tenure at Johns Hopkins. He explains how his research focus shifted to cosmology and he discusses his decision to switch to a faculty position at Maryland, where he became director of the Center for Fundamental Physics. At the end of the interview Sundrum explains his longstanding fascination with metaphysical ideas, and he reflects on the importance of developing intellectual maturity over the course of one’s career.

Interview with Mark Trodden, Fay R. and Eugene L. Langberg Professor of Physics, and Co-Director of the Center for Particle Cosmology at the University of Pennsylvania. Trodden describes the overlap between astronomy, astrophysics, and cosmology, and he recounts his working-class upbringing in England. He discusses his undergraduate education at Cambridge, where he focused on mathematics, and he explains his decision to switch to physics for graduate school at Brown, where he worked under the direction of Robert Brandenberger. Trodden describes the impact of the COBE program during this time, and he discusses his work on the microphysics of cosmic strings and topological defects and their effect on baryon asymmetry. He explains his decision to return to Cambridge for his postdoctoral research with Anne Davis and his subsequent postdoctoral appointment at MIT to work with Alan Guth. Trodden discusses his next postdoctoral position at Case Western, which he describes as a tremendously productive period, and he discusses the opportunities that led to his first faculty position at Syracuse. He notes the excellent graduate students he worked with at Syracuse, and he explains what is known and not known with regard to the discovery of the accelerating universe. Trodden describes why the theory of cosmic inflation remains outside the bounds of experimental verification, and he explains the decisions that led to his decision to join the faculty at Penn and his subsequent appointment as chair of the department. He discusses the work that Penn Physics, and STEM in general, needs to do to make diversity and inclusivity more of a top-line agenda, and he describes much of the exciting work his current and former graduate students are involved in. At the end of the interview, Trodden looks to the future and offers ideas on how physicists may ultimately come to understand dark energy and dark matter.

Interview with Steven Weinberg, Jack S. Josey-Welch Foundation Chair in Science and Regental Professor at the University of Texas at Austin. The focus of the interview is on how and when Weinberg became interested in cosmology, and how he defines it as a distinct discipline from astronomy and astrophysics. Weinberg explains that between the intensity of interest in particle physics in the 1950s and the speculative nature of cosmology, he had neither the interest nor the outlet to pursue cosmology in a rigorous way. He discusses some of the theoretical and experimental limitations at the time that kept cosmology in a largely “mystical” realm, and why the discovery of the microwave background by Penzias and Wilson “changed everything.” Weinberg explains what new questions can be considered as a result of evidence for a hot early universe, and he discusses when he first became interested in the formation of galaxies. He describes why the cosmological constant has bothered him for a long time, and he traces this problem back to Einstein and what Weinberg considers Einstein’s incorrect approach to his own theory. Contrasting his own experience as a graduate student, he cites John Preskill as his first student to pursue cosmology, and he explains that while his interests in particle physics and cosmology are generally separate, he always looks for intersecting research opportunities, which is well represented in the relevance of beta decay physics in the first three minutes of the universe. At the end of the interview, Weinberg surveys the value and problems associated with the term “Big Bang,” and he reflects on his career-long effort not to be dogmatic in his views on cosmology.

Interview with Andrei Linde, Harald Trap Friis Professor of Physics at Stanford. This discussion continues from the interview with Linde conducted by Alan Lightman in October 1987. He provides a detailed history on his improvement of Alan Guth’s work on inflation, which Linde dubbed “new inflation” and subsequently “chaotic inflation.” Linde describes the impact of Perestroika on Soviet scientists, and the pressures he felt in preparing for a series of talks in Italy, which contributed to his development of “eternal inflation.” He discusses his formative early communication with American physicists including Lenny Susskind and Norman Coleman, he describes his two-year visit at CERN as the Cold War was winding down, and he explains his decision to accept a faculty appointment at Stanford. Linde describes the alternating feelings of hope and despair in the 1980s regarding the possibility that inflation could be observationally verified. He explains the intellectual origins of self-generating fractals that sprout other inflationary universes and the value of compactification theory, and he explains the cultural relevance of his Russian heritage which compels him to value theoretical notions and not treat them in a throwaway manner that capitalism can encourage. Linde explains how and why multiverses can be testable and he reflects on the obvious philosophical or even spiritual implications of this proposition. He discusses the impact of the discovery of the accelerating universe and dark energy and how WMAP strained the theoretical viability of inflation. Linde explains why many string theorists have moved into investigating theories of quantum information, and at the end of the interview, he reflects on the value of competing theories to inflation and why, ultimately, he wants to see a major convergence of theories so that the origins of the universe are well understood. 

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 John Preskill, Richard P. Feynman Professor of Theoretical Physics at Caltech, and Director of the Institute for Quantum Information and Matter at Caltech. Preskill describes the origins of IQIM as a research pivot from the initial excitement in the 1970s to move beyond Standard Model physics and to understand the origin of electroweak symmetry breaking. He emphasizes the importance of Shor’s algorithm and the significance of bringing Alexei Kitaev into the project. Preskill discusses the support he secured from the NSF and DARPA, and he recounts his childhood in Chicago and his captivation with the Space Race. He describes his undergraduate experience at Princeton and his relationship with Arthur Wightman and John Wheeler. Preskill explains his decision to pursue his thesis research at Harvard with the intention of working with Sidney Coleman, and he explains the circumstances that led to Steve Weinberg becoming his advisor. He discusses the earliest days of particle theorists applying their research to cosmological inquiry, his collaboration with Michael Peskin, and his interest in the connection of topology with particle physics. Preskill describes his research on magnetic monopoles, and the relevance of condensed matter theory for his interests. He explains the opportunities that led to his appointment to the Harvard Society of Fellows and his eventual faculty appointment at Harvard, his thesis work on technicolor, and the excitement surrounding inflation in the early 1980s. Preskill discusses the opportunities that led to his tenure at Caltech and why he started to think seriously about quantum information and questions relating to thermodynamic costs to computing. He explains the meaning of black hole information, the ideas at the foundation of Quantum Supremacy, and he narrates the famous story of the Thorne, Hawking, and Preskill bets. Preskill describes the advances in quantum research which compelled him to add “matter” to the original IQI project which was originally a purely theoretical endeavor. He discusses the fact that end uses for true quantum computing remain open questions, and he surveys IQIM’s developments over the past decade and the strategic partnerships he has pursued across academia, industry, and at the National Labs. Preskill surveys the potential value of quantum computing to help solve major cosmological mysteries, and why his recent students are captivated by machine learning. At the end of the interview, Preskill reflects on his intersecting interests and conveys optimism for future progress in understanding quantum gravity from laboratory experiments using quantum simulators and quantum gravity.