Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session K07: PRIZE TALKS Big Bang Nucleosynthesis, Dark Matter, and Astronomical Random Number GeneratorsInvited Prize/Award
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Sponsoring Units: DAP DNP Chair: Dan Kasen, University of California, Berkeley Room: B131-132 |
Sunday, April 15, 2018 3:30PM - 4:00PM |
K07.00001: Hans A. Bethe Prize Talk: Big Bang Nucleosynthesis and probes beyond the Standard Model Invited Speaker: Keith Olive Big bang nucleosynthesis provides a window to the physics of the universe just seconds after the big bang. It predictions of the light element abundances of D, $^4$He, and $^7$Li can be compared with observational determinations. Over the last several years, significant progress has been made in the determinations of deuterium and helium abundances and most importantly results from Planck measurements of the microwave background have provided precise values for the baryon density of the universe, a key input used in abundance predictions. These predictions are also sensitive to the conditions when the temperature of the universe was $\approx 1$ MeV or $\approx 10^{10}$ K. Using inputs from the standard model of cosmology and particle physics yields excellent agreement between theory and experiment. Thus deviations from the standard model such as the number of particle degrees of freedom (often parametrized as the number of neutrino flavors) or the constancy of physical constants can be tested. [Preview Abstract] |
Sunday, April 15, 2018 4:00PM - 4:20PM |
K07.00002: Understanding Charge Exchange through Laboratory Astrophysics Measurements using an Electron Beam Ion Trap Invited Speaker: Gabriele Betancourt-Martinez Charge Exchange (CX) is a process in which a highly charged ion captures one or more electrons from a neutral atom or molecule into an excited quantum state during a close interaction. The electron's subsequent radiative cascade to the ground state produces characteristic line emission, often in the X-ray band. X-ray emission due to CX between solar wind ions and neutrals in comets and planetary atmospheres is ubiquitous in the solar system, and is also a significant foreground in all observations from low-Earth orbit. It is also likely that CX is common astrophysically, in any environment where hot plasma and cold gas interact. High-resolution studies of CX spectra have the potential to be extremely diagnostic of the emitting region, giving information about ion and neutral species, including charge state and abundances, their interaction velocity, and densities. However, in order to both properly identify any CX component in astrophysical spectra and make use of its diagnostic properties, we must be able to correctly model the emission. The most accurate theoretical treatments of CX are often prohibitively computationally expensive, experimental benchmarks at high spectral resolution are fairly scarce, and there is often poor agreement between models and data. We seek to build a better understanding of the atomic physics and spectral signatures of CX through high-resolution experimental data paired with theoretical calculations of CX. In this talk, I will present experimental results from an Electron Beam Ion Trap (EBIT) and an X-ray microcalorimeter which we use to benchmark CX models, and review our progress in understanding CX diagnostics and developing a more comprehensive and accurate CX theory. [Preview Abstract] |
Sunday, April 15, 2018 4:20PM - 4:40PM |
K07.00003: The Hunt for Astrophysical Neutrinos Invited Speaker: Shirley Li Astrophysical neutrinos are excellent probes of neutrino properties, the solar core, and high-energy cosmic accelerators. But their detection suffers from high backgrounds and from uncertainties in how we reconstruct and interpret events. For example, solar neutrino signals in Super-Kamiokande are overwhelmed by beta-decay backgrounds initiated by cosmic-ray muons. Meanwhile, the detection of high-energy astrophysical neutrinos in IceCube opened new ground for studying cosmic accelerators, but IceCube cannot effectively distinguish $\nu_\tau$ from $\nu_e$, as both generate similar-looking events. Using understanding of the common shower physics underlying both problems, I will show new methods to reject spallation backgrounds in Super-Kamiokande, applicable to their solar neutrino analysis, and to improve the measurement of flavors of astrophysical neutrinos in IceCube. [Preview Abstract] |
Sunday, April 15, 2018 4:40PM - 5:00PM |
K07.00004: The Long-Term Outcomes of Double White Dwarf Mergers Invited Speaker: Josiah Schwab Binary star systems composed of two white dwarfs are a natural outcome of stellar evolution. Angular momentum losses from gravitational wave radiation cause the binary system's orbit to shrink until the two white dwarfs merge. The final outcome of the merger depends primarily on the masses of the white dwarfs. Some potential outcomes, such as supernova explosions, may occur during or soon after the merger. Other outcomes, which I will refer to as "long-term" outcomes, occur as the merger remnant cools and its structure adjusts to the new state created during the energetic merger. In this talk, I will focus on the merger of two carbon-oxygen WDs. I will present simulations of the short-lived viscous disk initially present in these remnants and then show calculations that use the state-of-the-art MESA stellar evolution code to follow their thermal evolution. I will discuss the observational properties of these merger remnants and outline the interesting evolutionary process that leads to their final fate, which is likely collapse to a neutron star. The anticipated formation of a degenerate oxygen-neon core during this evolution necessitates an accurate treatment of the weak reactions that can drive its thermal and compositional evolution. I will discuss a series of calculations that use the MESA stellar evolution code to study degenerate oxygen-neon cores. These include previously neglected effects such as Urca-process cooling and are able to reach length-scales that directly connect full-star simulations to past studies of the onset of the collapse process. [Preview Abstract] |
Sunday, April 15, 2018 5:00PM - 5:18PM |
K07.00005: LeRoy Apker Award Talk: Bell's Inequality and Beyond with Astronomical Photons Invited Speaker: Calvin Leung Photons from distant astronomical sources can be used as classical random bits to conduct fundamental tests of quantum nonlocality and wave-particle duality. First, I report on a test of Bell's Inequality in which the measurement basis choices are determined by a pair of Milky Way stars in order to address the locality and freedom-of-choice loopholes. Explaining our 11-sigma Bell violation in a local realist framework would require a classical conspiracy exploiting the freedom-of-choice loophole to have acted 600 years ago. Second, I discuss the demonstration of a next-generation astronomical random number generator which can output 12 billion-year-old random bits generated by distant quasars with redshifts up to 3.9. Finally, I will discuss how I leveraged our instrumentation to obtain a new constraint on violations of the Weak Equivalence Principle, and report an upper bound complementary to existing results in the literature. [Preview Abstract] |
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