Inflationary universe

Interview with Robert H. Brandenberger, Canada Research Chair and professor of physics at McGill University. Brandenberger recounts his childhood in Switzerland as the son of organic chemists, and he describes his undergraduate education at the ETH Zurich in physics. He discusses his graduate research at Harvard to work under the direction of Arthur Jaffe, and he describes his first exposure to cosmic inflation. Brandenberger describes his postdoctoral appointment at the ITP in Santa Barbara where he worked with Neil Turok and Andreas Albrecht, and his subsequent postdoctoral work with Stephen Hawking at Cambridge. He explains his initial ideas on cosmic strings as an alternative to inflation and his encounters with Cumrun Vafa and Slava Mukhanov. Brandenberger describes the origins of string gas cosmology, its implications for a multiverse and how it was received among string theorists. He discusses his faculty appointment at Brown and he explains his decision to move to McGill where the opportunity to work with graduate students was stronger. Brandenberger surmises what string theory as a testable proposition would look like, and he reflects on some of the obvious philosophical implications of unknowability in the universe. He explains the difference between a toy model and a proper theory, and he conveys optimism that string gas cosmology will advance research on dark energy. At the end of the interview, Brandenberger reflects on the idea that string theory is "smarter than we are."

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 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.

In this interview, Paul Steinhardt, the Albert Einstein Professor in Science at Princeton, recounts his childhood in Miami and his undergraduate experience at Caltech, where he became interested in theoretical physics and where Feynman played a key influence on his development. He surveys where physics is stuck and compares similar challenges that both string theory and inflation are facing, and he explains his reasons for going to Harvard for his graduate work. Steinhardt describes being a student of Sidney Coleman’s and his focus on gauge theories. He discusses his postgraduate work at IBM Research and as a Junior Fellow at Harvard, and he explains the opportunity that led to his faculty appointment at the University of Pennsylvania. Steinhardt describes his increasing interest in cosmology and the influence of Alan Guth. He explains his dual interest in condensed matter physics and where he saw commonality with his cosmological research. Steinhardt conveys the importance of his collaboration with Dov Levine and he explains why he thinks the notion of a multiverse is nonscientific but not necessarily impossible. He explains his focus on quasicrystals for a time at the exclusion of cosmology, and the circumstances leading to his decision to join the faculty at Princeton which was a central point for research on the cosmic wave background. Steinhardt discusses his work on dark energy and the cosmological constant and his related interactions with Michael Turner. He describes his efforts to link the mystery of the Big Bang with the physics that can be understood after the beginning of the universe, and why the notion of the universe having a clear beginning is problematic. Steinhardt describes his frustration with string theorists who are working on abstract rather than existential research problems, and he surveys the technological advances that could make some of the intractable puzzles in cosmology testable, including the bouncing model of cosmology. He relates an epic story of mineral mining in pursuit of earthly quasicrystals, and at the end of the interview, Steinhardt describes his search for good puzzles as the common thread that connects all of his 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.

In this interview Joseph Silk discusses topics such as: influence of Boy Scouts in childhood; family background; high school education; early interest in mathematics; coaching by high school math teacher; math at Cambridge; influence of Dennis Sciama at Cambridge and decision to go into astronomy; fellow students at Harvard; character of Harvard astronomy department in the 1960s; David Layzer's opposition to the standard big bang model; first interest in the problem of galaxy formation and the union of hydrodynamics, radiative transfer, and cosmology at Woods Hole in summer of 1967; influence of Richard Michie; thesis work on interaction of matter and radiation in galaxy formation; ignorance about the first second of the universe and the origin of the primordial fluctuations; history of the growing confidence in the meaning of the cosmic background radiation; the philosophy of simplicity in physics; the role of the cosmic background rdiation in testing theories of galaxy formation; history of the horizon problem and Silk's attitude toward that problem; change in attitude as a result of the inflationary universe model; attitude toward the inflationary universe model; reasons why the model has become so popular; first introduction to and attitude toward the flatness problem; Silk's acceptance of appropriate initial conditions as explanations of cosmological problems; attitude toward the missing mass required by inflation; reaction to de Lapparent, Geller, and Huchra's work on inhomogeneities; ignorance of nature of inhomogeneities on scales betwen 20 megaparsecs and 2000 megaparsecs; worry over large-scale velocity fields and reported anistropies in the cosmic background radiation as challenges to standard models for the origin of fluctuations; importance of reported distortions in the spectrum of the cosmic background radiation (CBR) and difficulties of explaining such distortions if true; outstanding problems in cosmology: distortions in the CBR, galaxy formation, suitable initial conditions, satisfactory theory of inflation, value of omega; importance of metaphors and good verbal descriptions in scientific communication; interplay of theory and observation in cosmology; ideal design of the universe; question of whether the universe has a point.

Edwin Turner discusses his childhood experiences looking up at the stars; background of parents; encouragement and support of parents; early interest in science fiction and in history; childhood fascination with the scale of the universe; education at Massachusetts Institute of Technology (MIT); influence of Philip Morrison and Irwin Shapiro at MIT; preference for an open universe; dislike of missing mass that is invisible; scientific interests at MIT; graduate education at California Institute of Technology (Caltech); influence of Wallace Sargent; dislike of problem-set approach to education at Caltech; thesis work on dynamics of binary galaxies; influence of Ostriker-Peebles-Yahil work on dark matter and massive haloes in galaxies on Turner's observational thesis to measure masses of galaxies; interaction with Allan Sandage on philosophy of experimental science; Turner's surprise at finding dark matter in galaxies; community reaction to dark matter in 1975; continued belief in an open universe despite dark matter; history of N-body work on structure formation and correlation functions: influence of lecture by James Peebles, history of collaboration with Richard Gott and Sverre Aarseth; inability to measure omega by comparing N-body simulations with observations; reaction to inflationary universe model; reasons why the inflationary universe model has been so popular; Turner's reservations about the model; doing scientific projects because they can be done; introduction to and attitude toward the flatness problem; change in attitude after inflationary universe model; surprise at de Lapparent, Geller, and Huchra's results on large-scale inhomogeneities and its evidence for unknown processes: irrelevance of earlier work on correlation functions and lessening of Turner's expectations for what can be accomplished in cosmology; fear that cosmologists are heading in the wrong direction and underestimating the complexity of reality; use of imagery in science; interplay of theory and observation in cosmology and the divergence of the two; worry that we may have several untestable scenarios for the early universe; possible inability to reconstruct the history of the early universe; ideal design of the universe and desire for a rich and accessible universe; question of whether the universe has a point.

Interview covers Charles Misner's family background and childhood interest in science; influential chemistry teacher in high school; education at Notre Dame and mentorship with Arnold Ross; early interest in mathematics; encouragement of parents to go into science or to become a priest; graduate education at Princeton; work with John Wheeler on relativity and topology; introduction to cosmology by Jim Peebles in 1965; attitude toward the steady state model; Wheeler's preference for a closed universe; history of the flatness problem (the "Dicke paradox"); initial attitude toward the flatness problem; motivation for looking for mechanisms to isotropize the universe; the mixmaster model; history of the horizon problem; Misner's attempt to change the goals of cosmology from describing the universe to explaining it; Russian work on mixmaster type models; reaction of the community to the mixmaster model; change in Misner's view of the flatness problem after the inflationary universe model; attitude toward missing matter; problem of reconciling theory and observations with a flat universe; Misner's attitude toward the inflationary universe model; attitude of the community toward the inflationary universe model; attitude toward recent observations of large-scale structure; nature of the inhomogeneity of the universe; importance of Freeman Dyson's discussion of the fate of an open universe over very long time scales; role of visual pictures in science; relationship of theory and observation in cosmology; outstanding problems in cosmology; inflation, particle physics, quantum cosmology; ideal design of the universe; philosophy, science, and religion; necessity of the laws of physics; question of whether the universe has a point.

More discussion of the reasons why particle physicists began working on cosmology in the 1970s; importance of theoretical work by Kirzhnitz and Linde in 1972 on broken symmetries and phase transitions; current unreality of work on the very early universe; attitude toward the inflationary universe model; successes of the inflationary universe model; aesthetic attraction of a flat universe; acceptability of postulating that we live in a flat universe; introduction to and attitude toward the horizon problem; attitude toward the inflationary universe model; incidences of being worried about scientific problems that no one else is worried about; the anthropic principle and Dirac's large number hypothesis; reaction to de Lapparent, Geller, and Huchra's work on large-scale inhomogeneities; Weinberg worried that perhaps we have misinterpreted the cosmic background radiation; Weinberg's philosophy about strategy in science; the role of consensus in science and the importance of "standard" models; outstanding problems in cosmology: distance scale of the universe, value of the deceleration parameter, origin of structure; failure of theory to explain the observed large-scale structure; possible importance of WIMPs; prematurity of work on the early universe; ideal design of the universe; preference for universes in which initial conditions do not have to be specified; Weinberg's statement in The First Three Minutes about the lack of point to the universe.

Awareness in high school of the Sandage Program to observe the rate of expansion of the universe and awareness of the impending operation of the Mt. Palomar telescope; early reading in cosmology; prejudice toward the steady state model in graduate school because of its definite predictions; the reality of cosmology as a legitimate science; Weinberg's early interest in cosmology: influence of Herman Bondi's book; concern in the early 1960s over limited contact between theory and observations; early work in the 1960s on the neutrino version of Olber's Paradox and the possibility of a degenerate sea of neutrinos; preference for an oscillating universe as the next best thing after a steady state universe because you don't have to specify initial conditions; design of an experiment to search for degenerate neutrinos; Weinberg didn't take seriously his own work in cosmology in the 1960s; the importance of the discovery of the cosmic background radiation for making cosmology a legitimate science; the origin of Weinberg's book Gravitation and Cosmology; Weinberg's regret that he spent 1969-1971 working on a textbook when he should have been working on gauge theories in particle physics; history of the application of particle physics to cosmology.