I’ve been following Professor Yasunori Nomura‘s work this past year with tremendous interest, since he was one of the first theoretical physicists to publish a paper on the topic of the many worlds of quantum mechanics being one and the same as the eternally inflating multiverse. This perspective is one I consider to be extremely promising, both for its elegance and also for its ability to explain much that other theories cannot so easily address.
I was thrilled when attending a screening of the recent documentary film, “Particle Fever,” about the hunt for the Higgs boson to see Yasunori’s name up on the podium. I’d received an invitation to attend this UC Berkeley event through the Physics Department where I’d studied and received my degree many years ago. Dr. Yasunori Nomura was one of the panelists who talked about what we’re learning from the hunt for the Higgs boson after the show, along with Lawrence Hall, Marjorie Shapiro, Walter Murch, Mark Levinson, Petr Horava, Beate Heinemann, and Surjeet Rajendran. Dr. Nomura is a Professor at UC Berkeley at the Berkeley Center for Theoretical Physics, where his work is primarily focused on particle physics and cosmology.
CYNTHIA: Thank you so very much for taking time from your busy schedule to answer a few questions! I also want to thank you for writing such a clear and persuasive paper in the Journal of High Energy Physics, “Physical Theories, Eternal Inflation, and Quantum Universe.” You’ve also developed a new theoretical framework to describe dynamics of quantum gravity in low energy regimes, preserving locality. What’s so wonderfully exciting about bringing these ideas together is that you are presenting us with a view of general relativistic global spacetime being an emerging classical concept that arises from a special relativistic, quantum mechanical description of quantum gravity. When these concepts are applied to the idea of the multiverse, we then have a multiverse with no beginning and no end, but rather time that emerges locally in branches. Is this a fairly good summary of your most current perspective? And in what new directions is your work going next?
YASUNORI: Yes, that is a good summary of my perspective. Our world is quantum mechanical. Quantum mechanics governs how nature works at the deepest level, not just in small subatomic scales but also at the largest scale of the eternally inflating multiverse. At the same time, quantum mechanics is a “weird theory” which predicts many counter-intuitive phenomena, and from which the “normal world” we perceive emerges only in a certain limit. This includes concepts such as space and time. Furthermore, quantum mechanics is an intrinsically probabilistic theory—every prediction you make is probabilistic. My current effort focuses on developing a deeper understanding of these issues. What is the detailed microscopic mechanism underlying the emergence of spacetime? What does the probability really mean? How does understanding of these issues help revealing the so-far elusive quantum theory of gravity?
CYNTHIA: I love the way you describe our world as being quantum mechanical at the deepest level! This conceptualization has not been popularly embraced, perhaps due to the counter-intuitive “weirdness” of quantum mechanics. You make excellent points about quantum mechanics being intrinsically probabilistic, and I appreciate your emphasis on the importance of better understanding what probability really means. In the introduction of your 2011 paper, “Quantum Mechanics, Spacetime Locality, and Gravity,” you point out that, “Quantum mechanics introduced the concept of probability to physics at the fundamental level. This has led to the issue of the quantum-to-classical transition, in particular the measurement problem.” What is needed for us to better understand probability in a quantum world?
YASUNORI: What the probability in quantum mechanics really means is a deep question, with which people have been struggling for a century. At the most naive level, it means that when we prepare an ensemble of a large number of systems all of which are in an identical state, then the records of performing physical measurements on these systems are distributed according to what quantum mechanics predicts. Does this mean that we simply do not know enough details of the systems, and if we do, then we can predict the outcome of measuring each member of the ensemble with certainty? People certainly wondered this possibility in early days in developing quantum mechanics, but we are now almost certain that this is not the case. In quantum mechanical world, the outcome of a measurement is intrinsically probabilistic—the probabilistic nature is not a manifestation of our incomplete knowledge of the system. A question then arises when we ask what happens if we make a “single” measurement on “a” system in our universe. According to quantum mechanics, the result is “probabilistic,” but what does that really mean? Where is the ensemble? Are there many universes which are “distributed” according to the prediction of quantum mechanics? This is where the necessity of considering many universes—or multiverse—comes in. We need to consider cosmology in a deepest sense to really address this problem.
CYNTHIA: This suggests there is a deeper interconnectedness that goes beyond any “single” measurement on “a” system that is occurring everywhere–and not just in the realm of quantum particles, because we cannot assume that any given experiment is closed off from its surrounding environment. We definitely require an understanding of probabilities beyond mere statistical frequencies, since we can’t run experiments on multiple versions of the universe! What are your thoughts about the value of the Bayesian interpretation of probability for quantum cosmology–the idea that before we start measuring probabilities, we must set initial assumptions about the probabilities?
YASUNORI: Yes, the issue is certainly relevant beyond the realm of quantum particles at small scales. Quantum effects are there even at large distances—they are simply hard to recognize for an observer like us living in “a branch” of a complete quantum state. We still do not know exactly what form the physical law that allows us to address this issue will take, but I can certainly imagine that some sort of Bayesian ways of thinking may play an important, and perhaps even crucial, role in formulating such a law. In fact, there are already several hints to move forward, based on consistency of quantum cosmology. (Another obvious clue is that the new rule must reduce to the standard Born rule in situations in which an ensemble is explicitly available to an observer.) Perhaps, explorations of this issue may lead to a new theory beyond quantum mechanics, not just reinterpretation (or reformulation) of the standard quantum mechanics.
CYNTHIA: Quantum cosmology is an especially exciting field right now, as it is becoming clear that multiverse theories can be modeled using computer simulations that can be compared to cosmic background radiation. When you envision a new theory beyond our current conceptualization of quantum mechanics, what ideas do you find most interesting now?
YASUNORI: Yes, quantum cosmology is an especially exciting field right now because of observational and theoretical evidence pointing to the multiverse, gathered in the last decade or two. We are, however, not at a stage in which we can simulate the multiverse as we do for cosmic background radiation. The problems we are struggling are still conceptual: what is the probability in the cosmological context, etc. I am, however, optimistic about near future progress. One idea which I think promising, and which I have been pursuing, is that “time” we perceive emerges only locally in relevant branches (e.g. in our own universe) in the static multiverse state. This would solve many conceptual issues such as what is the beginning or end of the multiverse.
CYNTHIA: Considering time to be more of a variable than a constant in the multiverse is fascinating and mind-bending. We now have measurements from our most accurate strontium atomic clocks showing that time elapses more slowly at lower altitudes, influenced by gravity, so a clock positioned just a few centimeters higher will read a different time. NIST’s chief timekeeper, Tom O’Brian, recently stated in an NPR interview that, “My own personal opinion is that time is a human construct.” Could you describe a little bit more about how might we envision time as being something we perceive locally in relevant branches of the multiverse–is there some way to visualize such a thing?
YASUNORI: What we call time is nothing more than (a very special form of) correlations between physical objects. Consider throwing a baseball. It is usually stated that the baseball then moves (relative to the earth) as “time passes.” What is really happening, however, is that the relative location between the baseball and the earth is correlated with configurations of other physical systems, e.g. the location of the hands of a clock, relative configurations of the Sun, Earth, and Moon (although their changes are minuscule in the timescale of the motion of the baseball), configurations of synapses in your brain, etc. To describe all these correlations, one may introduce some parameter “t” and write the configurations of the systems as functions of this “spurious” parameter t as we describe a curve in a two-dimensional plane using a parametric representation: (x(t), y(t)). This parameter t is precisely what we call time—it does not really “exist” as a physical object!
A real question then is why there exists such a special form of correlations between configurations of various physical systems, more specifically correlations that are described in a simple manner using a single spurious parameter t. This is what really must be explained, which my static quantum multiverse proposal is trying to address. Note that these special corrections (i.e. time) need not exist in all the branches of the multiverse state. We only know experimentally that they exist in the branches corresponding to our universe.
CYNTHIA: You point out that our conceptualization of infinitely large space that we associate with eternal inflation is really just an illusion, and a more accurate way to describe everything is that we exist within an intrinsically probabilistic multiverse. The vastness of eternally inflating space can thus be found in probability–in which an initial state evolves into a superposition of states, with branches occurring whenever bubble universes burst forth. In your “Static Quantum Multiverse” 2012 paper, you explain how the multiverse need not evolve in order to be consistent with an arrow of time–which presents a completely different picture of cosmology than the currently popular sense of infinitely large space. Within this static quantum multiverse, can you envision there being a place for subjective observation with its associated sense of past, present and future—so important to people, as Bernard d’Espagnat’s observes, “Time is at the heart of all that is important to human beings.” For example, when imagining ourselves throwing a baseball, is there anything we can identify as being ‘now’–the present moment?
YASUNORI: You correctly summarize that the vastness of eternally inflating space can be found in probability space. In a sense, the “Static Quantum Multiverse” proposal simply says that the vastness of time should also be found in the probability space. In this picture, the (static) multiverse state contains many “observers,” e.g. myself, at “different times,” each of whom has his/her own sense of past, present and future. In your example, each of these “observers” (which we usually describe as a single observer in different moments) has his/her own sense of now, with the baseball located in the place determined mostly by the Newtonian mechanics. I can’t affirm that the absence of the absolute notion of ‘now’ is not a problem, but I think it is not.
CYNTHIA: I appreciate how your static quantum multiverse model’s inclusion of probability space and time provides such an elegant view of the cosmos while allowing for free will and unique individual experience. Thank you for sharing some of your fascinating ideas and observations about quantum cosmology, time and space! In addition to reading your many publications–which number 111 to date, according to ResearchGate–how best can people follow your work and what you are doing?
YASUNORI: It is my pleasure. ResearchGate is one option. Another possibility is to use an author search in INSPIRE, the High Energy Physics information system built by CERN, DESY, Fermilab and SLAC: http://inspirehep.net/search?ln=en&ln=en&p=author%3AY.Nomura.1&of=hb&action_search=Search&sf=earliestdate&so=d&rm=&rg=250&sc=0/ I will also be updating my homepage: http://physics.berkeley.edu/people/faculty/yasunori-nomura/
Cynthia Sue Larson is the best-selling author of six books, including Quantum Jumps, Reality Shifts, Aura Advantage, High Energy Money, and Karen Kimball and the Dream Weaver’s Web, and the Aura Healing Meditations CD. Cynthia has a degree in Physics from UC Berkeley, and she discusses consciousness and quantum physics on numerous shows including the History Channel, Coast to Coast AM, and BBC. You can subscribe to Cynthia’s free monthly ezine at: http://www.RealityShifters.com