Axions

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Interview with Katherine Freese, Director of the Weinberg Institute for Theoretical Physics, the Jeff and Gail Kodosky Endowed Chair in Physics at UT Austin, and the Director of the Texas Center for Cosmology and Astroparticle Physics (TCCAP). Freese begins the interview with an overview of terminology, such as cosmology, astrophysics, and astroparticle physics and the delineation between these fields. Then she describes her childhood in Bethesda, Maryland where both her parents were scientists. Freese recalls beginning college at age 16, starting at MIT and then transferring to Princeton. She recounts taking time off after her undergraduate studies, before deciding to pursue graduate studies. Freese began grad school at Columbia but switched to the University of Chicago to work on neutrino physics with David Schramm. She discusses her first post-doc at Harvard, working on WIMPs and dark matter, and then her second post-doc at Santa Barbara with Frank Wilczek. Freese then recalls returning to MIT as a professor where she worked with Alan Guth and Josh Frieman on cosmic inflation. She talks about her transition to the University of Michigan and the exciting developments in cosmology at the time, as well as her introduction to dark energy. Freese describes her more recent involvement with NASA’s SPIDER experiment, as well as the honor of being named to the National Academy of Sciences. Freese discusses the amazing opportunity of being the Director at the Nordic Institute for Theoretical Physics and ends the interview with her hopes for the future of cosmology, namely her hope for finding dark matter.

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.

Elliott Bloom, Professor Emeritus of Particle Physics and Astrophysics at SLAC, recounts his childhood in Brooklyn and then in Los Angeles, and he describes his early interests in physics. He discusses his undergraduate experience at Pomona College where he became interested in particle physics and cyclotrons. Bloom describes his graduate work at Caltech, where he worked under the direction of R.L. Walker and did his thesis experiment on studying gamma ray production of charged pions from hydrogen or deuterium. He discusses his postdoctoral research at SLAC to work with Richard Taylor, who was building spectrometers in End Station A at the end of the linear electron accelerator. Bloom discusses his early interests in online computing and he describes the origins of the Parton model and his collaboration with Joe Ballam on BC-42. He explains his original involvement with axion research and the significance of the DORIS-II storage ring at DESY. Bloom discusses his subsequent work at the SLAC B-factory on PEP-II, he describes his interests in the COBE satellite, and he explains SLAC's entrée into astrophysics. He discusses the collaborative effort with NASA on the GLAST experiment and his focus with DOE support to understand dark matter. At the end of the interview, Bloom reflects on his career trajectory as part of a larger narrative of particle physicists who became engaged in astrophysics later in their careers, and why it is important for physicists to remain open to new avenues of inquiry.