Bulletin of the American Physical Society
2018 Annual Meeting of the APS Four Corners Section
Volume 63, Number 16
Friday–Saturday, October 12–13, 2018; University of Utah, Salt Lake City, Utah
Session L07: Astrophysics: Forces and Particles |
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Chair: Darin Ragozzine, Brigham Young University Room: JFB B-1 |
Saturday, October 13, 2018 11:20AM - 11:44AM |
L07.00001: A Hunt for Dark Matter: a Tale of Sensitivity and Direction Invited Speaker: Dinesh Loomba We are now in the era of precision cosmology, where we know the age of the Universe, the geometry of space, the total energy density and what types of energy and matter contribute to it. Measurements suggest that ordinary matter, composed of protons and neutrons, is a mere 18% of the gravitational mass in the Universe. The rest is dark, and so far we infer its existence only gravitationally. The goal of detecting and identifying dark matter is arguably one of the most important problems in 21st century science. We briefly review some of the observational evidence for dark matter, and describe the experimental efforts to detect a signature critical for its discover. |
Saturday, October 13, 2018 11:44AM - 11:56AM |
L07.00002: Formation of dark energy stars Philip Beltracchi, Paolo Gondolo Dark energy stars are finite size astrophysical objects with an interior equation of state $p=-\rho$. Examples are self gravitating false vacuum bubbles, vacuum non singular black holes, and gravastars. We present a time-dependent solution of Einstein's field equations that describes the collapse of a spherical system from an initial state of positive pressure to a final state with a dark energy core. Our solution has no singularities, no event horizons, and does not violate the weak or null energy conditions. |
Saturday, October 13, 2018 11:56AM - 12:08PM |
L07.00003: Sources for biconformal gravity Davis W Muhwezi, James T Wheeler Biconformal gravity is a 2n-dimensional conformal gauge theory with a curvature linear action that has been shown to reproduce scale invariant general relativity on the cotangent bundle of n-dimensional spacetime. We explore Yang-Mills sources for biconformal gravity. The questions we seek to clarify are whether the augmented field equations reduce the Yang-Mills sector to n-dimensional Yang-Mills theory and yield the appropriate energy-momentum tensor as the gravitational source. |
Saturday, October 13, 2018 12:08PM - 12:20PM |
L07.00004: Probing the Existence of New Particles using Compact Objects Hyun Lim In the next few years, upgraded Advanced LIGO may see gravitational waves from thousands of compact object mergers such as binary black holes and neutron stars. This marks the beginning of a new era of precision measurements in physics. In this work, we explore the possibility that the dynamics of compact objects can be used to probe the existence of new particles including dark matter constituents. With a massive scalar field, a rotating black hole is unstable to a superradiant instability. This process extracts rotational energy from the black hole. We explore this process as a way to look for QCD axions, dark photons, and other ultralight bosons with a Compton wavelength comparable to the black hole’s radius. |
Saturday, October 13, 2018 12:20PM - 12:32PM |
L07.00005: Update on the analysis of near horizontal muons with HAWC Ahron Barber In this talk, I will present an update on the observation of near horizontal muons with the High Altitude Water Cherenkov (HAWC) gamma and cosmic ray observatory. The observatory is located at an altitude of 4100 meters a.s.l. on the Sierra Negra volcano in Mexico. The HAWC detector is composed of 300 large water tanks which are 7.3 m in diameter and 4.5 m tall and positioned over an an area of approximately 22,000 square feet. The positioning and height of the water tanks allows for HAWC to act as a Hodoscope for muons with trajectories very near 90 degrees zenith. This presentation will provide an update on work to obtain the rate of near horizontal muons corresponding to a minimum energy needed to penetrate the rock depth from Pico de Orizaba or Seirra Negra. |
Saturday, October 13, 2018 12:32PM - 12:44PM |
L07.00006: Gamma-rays observed at ground level in coincidence with downward lightning leaders Jackson Remington, John Belz, Rasha Abbasi, Ryan Le Von, William Rison, Mark Stanley, Dan Rodeheffer, Paul Krehbiel The Telescope Array Surface Detector (TASD) is a cosmic ray observatory in western Utah, consisting of over 500 detectors and covering over 700 km2. Between 2014 and 2016, ten bursts of gamma-ray showers were observed in coincidence with downward-propagating negative leaders in lightning flashes by the TASD. For three of the showers, full spatial and temporal structure was recorded using an implementation of the Lightning Mapping Array (LMA). During the other seven events, electric field data was recorded. Information on each of the flashes was also provided by the National Lightning Detection Network (NLDN). Each shower consisted of a burst of 2-5 TASD events during the first 1-2 ms of lightning development. Detector footprints and waveforms suggest the showers were composed primarily of downward-beamed gamma radiation. Every flash began with downward negative leader breakdowns approximately 3-5 km above ground level. We conclude that the showers are terrestrial gamma-ray flashes (TGFs), similar to those observed by satellites. From the ground, however, observations are more sensitive and representative of source activity. |
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