Quantum Gravity, Atom Condensate Analogs, and Beyond

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The grant will support research projects on several aspects of gravitational physics, ranging from astrophysical to laboratory analogs to quantum gravity. These projects are aimed at: 1) learning more about the magnetic physics involved in the powerful processes accelerating particles around black holes and neutron stars, which could assist in the interpretation of observations of such sources made with various sorts of telescopes; 2) exploring a mechanism by which neutron stars might source a hypothetical "axion" field, which is a candidate for solving a theoretical puzzle of nuclear physics and is a candidate for the "missing mass" (a.k.a. "dark matter") in the Universe; 3) working with experimentalists to study close analogies between the physics of ultra cold atomic condensates and the behavior of quantum fields in the expanding universe and the Hawking radiation from black holes. This work can stimulate new insights into the properties of atom condensates, and provide laboratory confirmation and perspectives on otherwise purely theoretical fundamental theory; 4) approach the unsolved problem of reconciling Einstein's curved spacetime theory of gravity with the principles of quantum physics. The first three of these project categories include significant interdisciplinary connections to astrophysics, plasma physics, and atomic physics, which may enhance synergy between different research communities and methods, and therefore stimulate progress in scientific understanding. The results of the proposed research will be disseminated through written articles, as well as seminars, conference talks, and colloquia. The PI will provide instruction and mentoring to graduate and undergraduate students, regarding scientific research, writing, and verbal communication. The PI will design and implement instruction in a University of Maryland summer programs for rising 9th graders and for high school girls interested in physics. All of these activities will contribute to technical training and scientific literacy, as well as understanding and appreciation of the insights of physics.Specific research topics in category 1) above include a sharp formulation of magnetic helicity of twisted magnetic field lines in a general relativistic setting, and in the presence of boundaries such as the surface of a neutron star or the horizon of a black hole, and the impact of cyclotron motion on the stagnation surface, which defines the boundary between the charges that are gravitationally pulled to the black hole or neutron star and the charges that are flung outward along magnetic field lines by centrifugal force. Research under 2) aims to discover new ways of observing or constraining an axion field by studying the consequences of copious axion production sourced outside neutron stars, first analytically, and potentially later in numerical simulations with a computational collaborator. The hypothesis that such axion fields are implicated in fast radio bursts will also be explored. In category 3), one project will quantify the effect of variations in the number of condensate atoms on laboratory measurements of the correlation function associated with Hawking radiation. This is necessary in order to interpret those observations. Another project will analyze the theory and upcoming observations of mode modulation (analog Hubble friction) in expanding Bose-Einstein condensates. A third project in this area will explore approaches to experimental measurement of phonon or magnon creation in analog expanding universes. Observations might be possible within the time frame of the award. Finally, one goal of the research under 4) is to develop understanding of quasi-localized quantum gravity, using exact quantization of the 2+1 dimensional theory with a negative cosmological constant, within a spacetime region that is the causal domain of dependence of a disk with a fixed boundary metric. Another is to learn how to apply perturbative renormalized quantum gravity near horizons, to determine whether, as has long been suspected, gravitational interactions quench two point correlation functions when one of the points approaches a horizon.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.