Dark matter

In this interview, Saul Perlmutter, Professor of Physics at UC Berkeley and Staff Scientist and senior faculty member at Lawrence Berkeley National Laboratory, discusses his life and career. Perlmutter shares that his research has not been slowed down by the pandemic by happy coincidence that he is currently focused on remote data analysis, and he recounts his childhood in Philadelphia where he was educated in Quaker schools. He discusses his early fascination with quantum mechanics and his decision to go to Harvard for his undergraduate education, where he cemented his interests in experimental physics. Perlmutter explains his decision to go to Berkeley for graduate school, where he worked in Buford Price’s group before Richard Muller became his graduate advisor. He discusses his early awareness of the cosmic microwave background and how he became involved with robotic searches for supernovae. Perlmutter describes the importance of NASA’s BITNET program as a way to connect observatory data worldwide to the computer systems at Berkeley, and he explains the intellectual and observational connections between the inflation, expansion, and acceleration of the universe. He discusses his postdoctoral research at Berkeley, and the circumstances leading to him becoming leader of the supernova group and how the DOE became more involved in astrophysics funding. Perlmutter explains the group’s focus on deceleration and he conveys the difficulties in scheduling telescope time to demonstrate spectroscopy proof of type Ia supernovae. He describes the origins of the SNAP satellite project, some of the early theoretical discussions on the nature of dark energy, and when, finally, his group secured long-term support from the Lab. Perlmutter narrates his first interactions with Brian Schmidt and Adam Riess and he describes the batch technique that could predict the discovery of supernovae, which vastly improved the efficiency of scheduling time on large telescopes. He explains the role of dark matter in speeding up the universe’s expansion, and he narrates the celebration with his team when he won the Nobel Prize and how he has chosen the use the political platform that comes with this recognition. Perlmutter discusses his interest in studying climate change, and at the end of the interview, he conveys his excitement about future observational discovery in astrophysics and cosmology.

Interview with Sarah Demers, Horace D. Taft Associate Professor of Physics at Yale University. Demers explains her academic lineage connection to Taft, and she surveys the challenges of remote work in the pandemic. She recounts her Vermont childhood growing up in the church as the daughter of a United Methodist minister and how her family discussed the compatibility of science and religion. Demers discusses her undergraduate experience at Harvard and her early struggles with physics. She describes her relationship with Melissa Franklin and her first experiences with the CDF detector project at Fermilab. Demers explains her decision to go to the University of Rochester for graduate school where she studied under the direction of Kevin McFarland, and she describes plotting the Z boson at Fermilab. She describes her first job teaching at Roberts Wesleyan College and her subsequent appointment as part of SLAC’s team for ATLAS at CERN, where she developed an infinity for the triggers of experiments. Demers explains the opportunities that led to her faculty appointment at Yale, and she describes the interests that led to her book on physics and dance. She discusses her ongoing collaboration with ATLAS, the tenure process at Yale, and her work on Mu2e. Demers describes the “aesthetic hints” that may prove to be physics beyond the Standard Model, and she explains why the LHC can play a pivotal role in the search for dark matter. At the end of the interview, Demers discusses her current interest in tau leptons, she describes the issue of bias as a blockage to improving diversity in the field, and she reflects on the technological improvements that have propelled her field forward. 

Interview with Phillip James Edwin Peebles, Albert Einstein Professor of Science, Emeritus, at Princeton University. Peebles describes his enjoyment in pursuing the issues in cosmology that are most interesting to him in retirement and he explains his appreciation for the importance of taking a sociological perspective to science. He describes his first exposure to cosmology as a field to specialize in during graduate school and he surveys some of the experiments and observational advances that have propelled theoretical cosmology. Peebles recounts his childhood in Manitoba, and he discusses his undergraduate education at the University of Manitoba. He describes arriving at Princeton in 1958 and how he became a student of Bob Dicke's. Peebles discusses his thesis research on the possibility that the fine-structure constant might be evolving. He describes staying at (and never leaving) Princeton for his postdoctoral work, and some of the exciting promises of infrared astronomy and radio astronomy. Peebles conveys the simple process of joining the faculty, and he describes the developments leading to the prediction of the cosmic microwave background. He discusses the trend of particle theorists pursuing questions in cosmology, and he reflects on the impact of the Vietnam era on Princeton. Peebles conveys the significance of the introduction of cold dark matter and his perspective on the inflationary theory of the universe. He explains why LambdaCDM has become standard in the field and why COBE was so important. Peebles surveys the many observational projects that are currently being planned, and he reflects on the "buzz" that he felt in advance of winning the Nobel Prize. He describes how his life has been affected by this honor, and he reflects on how the Department of Physics has changed over the course of his long career. At the end of the interview, Peebles emphasizes his interest in remaining close both to theory and experimentation, and he shares his sense of curiosity at what clues might be found from the epoch of light element production in the very early universe.

Interview with Elena Aprile, Centennial Professor of Physics at Columbia University. Aprile describes the feeling of just having been elected to the National Academy of Science and she describes how the XENON Dark Matter search has continued despite the pandemic. She explains why so much of physics is devoted to try to understand dark matter and where she sees the interplay of theory and experiment toward that end. Aprile describes why finding dark matter will mean finding new physics beyond the Standard Model, and she recounts her upbringing in Milan and her developing interests in physics during high school. She describes her first visit to CERN when she was a student at the University of Naples and what it was like to meet Carlo Rubbia. Aprile discusses her graduate work at the University of Geneva where she worked on scattering protons to study time violation effects. She explains her interest in the UA1 and UA2 experiments at CERN and her work on noble liquid detectors, her appointment at Harvard, and her first involvement with radiation spectroscopy. Aprile narrates her realization that xenon would be valuable for astrophysics and dark matter specifically, and she describes the origins of the LXeGRIT telescope project. She explains why Gran Sasso was chosen on the site of the XENON experiment and some of the technical and economic challenges in dealing with xenon on the scale required to search for dark matter. Aprile reflects on the difficulties she has faced as a woman in her field, and she describes the competitive value in having the LZ experiment and its search for dark matter. She explains how one goes about searching for dark matter without knowing what dark matter is. At the end of the interview, Aprile imagines what it will mean to find dark matter, what mysteries it will solve, and why she will remain steadfastly cautious before confirming the discovery. 

Interview with John Ellis, Clerk Maxwell Professor of Theoretical Physics at King’s College London, and Visiting Scientist at CERN. Ellis discusses the g-2 experiment at Fermilab and where he sees current efforts geared toward understanding physics within the Standard Model, and pursuing new physics beyond it. He recounts his childhood in a small town north of London and his innate interest in physics before he understood that it was a proper field of study. Ellis discusses his education at Cambridge and the department’s strength in particle physics, general relativity, and cosmology, and he explains the relevance of the deep inelastic scattering research at SLAC for his thesis on approximate symmetries of hadrons. He describes the intellectual influence of Bruno Zumino and his decision to go to SLAC for his postdoctoral research to work on scale invariance. Ellis discusses his subsequent research at Caltech and he explains why he would have appreciated more the significance of asymptotic freedom had he better understood field theory at that point. He discusses his subsequent position at CERN and is collaboration with Mary Gaillard on semileptonic decays of charm. Ellis narrates the famous “penguin diagram” that he developed with Melissa Franklin and his interest in grand unification and how it differs from the so-called “theory of everything.” He describes the optimism in the 1980s that supersymmetry would be found and its possible utility in the search for dark matter. Ellis discusses his involvement with LEP and axion physics, and he reflects on the spirit of competition and collaboration between ATLAS and CMS in the run up to the Higgs discovery. He explains the new questions that became feasible as a result of the discovery and his interests in both gravitational waves and supernovae. Ellis describes the AION experiment, the important physics research currently in the works in China, and key recent developments in quantum gravity. At the end of the interview, Ellis conveys his belief in the importance of science communication, he minimizes the importance of the h-index as a measure of excellence, and in reflecting on his own career, he cautions against younger physicists becoming overly-specialized. 

Interview with Hiranya Peiris, Professor of Astrophysics at University College London and Director of the Oscar Klein Centre and Professor of Cosmo-Particle Physics at Stockholm University. Peiris describes her dual affiliation, she discusses diversity in STEM over the past year, and she surveys the current interplay between theory and observation in her field. She recounts her childhood and family heritage in Sri Lanka and the circumstances that led her family to relocate to the United Kingdom. Peiris describes her interests in math and science the opportunities that led to her enrollment at Cambridge as an undergraduate and a formative experience at JPL in California. She explains her decision to pursue a PhD at Princeton, where she worked with David Spergel on WMAP. Peiris discusses her postdoctoral appointment as a Hubble fellow at the University of Chicago to continue to work on WMAP, and her subsequent work as a Halliday fellow at Cambridge. Peiris discusses her work on the Lyman-alpha forest and her faculty appointment at UCL where cosmology was just coming into maturity. She conveys the excitement as WMAP results were becoming available and her contributions to the search for dark matter. Peiris explains why the LSST project is so significant, what it was like to win the Breakthrough Prize, and the gratitude she feels by having eminent physicists as mentors. At the end of the interview, Peiris emphasizes the importance of following inquiry into the most fundamental questions surrounding gravity and space time, and why Stephen Hawking remains an intellectual inspiration to her.

Interview with Sylvester James Gates, Jr., Ford Foundation Professor of Physics and Director of the Theoretical Physics Center at Brown University. Gates discusses his preparations to lead the APS and the value of his service for PCAST for this new role. Gates recounts his family heritage and he discusses his father’s military service and the death of his mother. He explains how his family navigated racist challenges during his upbringing in El Paso and then in Orlando and how he navigated his own intellectual abilities in school. Gates explains his interest in physics in high school and the opportunities that led to his admission at MIT for his undergraduate work. He recounts the many mentors who made a positive impression on him and he explains his realization that his specialty would be at the boundary between math and physics. Gates describes his earliest interactions with string theory and he explains his decision to remain at MIT for his graduate work to work with Jim Young on supersymmetry. He paints a broader picture of supergravity research at this time and the rising importance of computers for this work. Gates describes his postdoctoral research at Harvard as a Junior Fellow, where he worked closely with Warren Siegel, and he describes his decision to join the faculty at MIT after a subsequent postdoctoral position at Caltech. He addresses Shelly Glashow’s criticism of string theory, and he explains his decision to leave MIT for a faculty position at the University of Maryland. Gates reflects on his teaching and mentoring career at Maryland, he describes his time at Howard University, and he discusses the broader issue of diversity in physics and AIP’s TEAM-UP Report. He describes his more recent interests in graph theory and the broader effort to unify gravity with the other forces. Gates reflects on how he became an advisor to President Obama for PCAST and how he worked with John Holdren to translate reports into policy changes. He explains his decision to go emeritus at Maryland and to take a new position at Brown, and why joining the Watson Institute was an attractive part of the offer. Gates reflects on assuming leadership at APS during the twin crises of Covid and racial strife, he surveys the state of string theory and high energy physics, and he explains why supersymmetry might offer a path to understanding dark matter. At the end of the interview, Jim conveys his hope that his work in math will yield deep insights into nature, and he considers the possibility of pursuing an autobiographical project.

Interview with Kevin Lesko, Senior Physicist at Lawrence Berkeley National Lab and former Spokesperson for LUX-ZEPLIN (LZ), an international collaboration searching for dark matter. Lesko explains why so many different kinds of physicists are involved in dark matter searches and how theorists have provided guidance for experimental and observational work to understand dark matter. He recounts his upbringing in northern California, the scientific influence of his parents and older siblings, and his decision to attend Stanford, where he worked on a tandem Van De Graaff in the nuclear physics lab. Lesko discusses his graduate work at the University of Washington, where he worked under the direction of Bob Vandenbosch on nuclear fission research, and he describes his postdoctoral appointment at Argonne, where he pursued experiments in nuclear fusion and neutrino physics. He explains his decision to join the staff at Berkeley Lab and how his interests centered increasingly on astrophysics with the Sudbury Neutrino Observatory. Lesko discusses his collaborations in Japan and KamLAND’s discovery of the absolute measurement of neutrino oscillations and the origins of the Homestake collaboration. He describes the transition of support for Homestake from the NSF to the DOE and he explains his entrée to the LUX collaboration and the reasons for the merger with ZEPLIN. Lesko explains how LZ needs to be ready to detect dark matter either as a singularity or is comprised of multiple components, and he considers what it might look like for dark matter to be detected. He recounts LZ’s success in ruling out dark matter candidates and he reflects on LBNL serving as a home base while his collaborative research has always been far-flung. At the end of the interview, Lesko considers what we have learned about the universe as a result of LZ, and why mystery and curiosity will continue to drive the field forward.

Philip Pincus is a Distinguished Professor of Materials, Physics, and Biomolecular Science at UC Santa Barbara. In this interview, he explains the origin of his nickname “Fyl,” he recounts his childhood in San Francisco, as well as his decision to study physics at Berkeley and his mentorship by Charlie Kittel. Pincus describes his thesis research on temperature dependence of anisotropy energy, and nuclear spin relaxation in magnetic materials. He describes his postdoctoral work at Saclay and his faculty appointment at UCLA, and he describes working with de Gennes and Alan Heeger. Pincus describes his contributions to dirty type II superconductors and the excitement surrounding early research on liquid crystals. He explains his decision to join the research lab at Exxon Mobil and he describes the basic science research culture there and his increasing focus on soft matter physics, which he continued to pursue at UC Santa Barbara in the Chemical Engineering Department. Pincus discusses his current interests in water and cohesive energy, and at the end of the interview, he reflects on the growth of soft matter physics out of his original interest in solid state physics, and he explains why condensed matter theorists might have something to offer dark matter research.

Edward “Rocky” Kolb is the Director of the Kavli Institute for Cosmological Physics at the University of Chicago and the Arthur Holly Compton Distinguished Service Professor of Astronomy at the University of Chicago. In this interview, Kolb explains how he acquired his nickname and he recounts his upbringing in New Orleans and his habit of spending time in the local library, where he developed his interest in science. He describes the financial constraints that compelled him to attend the University of New Orleans for college, and he characterizes his education there as broad but not deep, which caused him to consider a wide range of specialties for his graduate research at the University of Texas. Kolb describes working with his graduate advisor Duane Dicus in applying particle physics to cosmological questions, and he summarizes his dissertation research on the effects of axions in stars. He discusses his postdoctoral research with Willy Fowler at Caltech, and he emphasizes the influence of Allan Sandage on his decision to focus on cosmology.  Kolb describes his second postdoctoral fellowship at Los Alamos where he joined the burgeoning astrophysics group in the Theoretical Division to work on Big Bang nucleosynthesis.  He explains his decision to join the astrophysics group at Fermilab, where he collaborated closely with Michael Turner and benefited from the support of Leon Lederman. He describes his developing interest in supersymmetry and neutrino oscillations, he describes the impact of Alan Guth’s lectures on inflation, and he explains his increasing involvement with the astronomy and astrophysics department at the University of Chicago culminating with an offer for him to become chair of the department.  He describes his objectives and achievements in that position, he explains how he maintained research interest in creating particles from the vacuum, and he describes how this research could be of value in the ongoing quest to understand dark matter. At the end of the interview, Kolb reflects on the different approaches that religion and science take to understanding reality, and he explains why he is most optimistic that understanding dark matter is the most likely major future breakthrough in his field.