Bulletin of the American Physical Society
2015 Joint Fall Meeting of the APS and AAPT New England Sections
Friday–Saturday, November 6–7, 2015; Hanover, New Hampshire
Session B1: Contributed Oral Presentations in Cosmology, Astrophysics & Particles |
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Chair: Marcelo Gleiser, Dartmouth College Room: Wilder Hall 104 |
Saturday, November 7, 2015 8:30AM - 8:42AM |
B1.00001: Do Single-Degenerate Type Ia Supernovae Generally Lead to Normal Type Ia Supernovae? Robert Fisher Type Ia supernovae (SNe Ia) serve as crucial standardizable candles for cosmology, yet we still do not fully understand their origins. Recent observational and theoretical progress has favored merging and helium-accreting sub-Chandrasekhar mass white dwarfs (WDs) in the double-degenerate and the double-detonation channels, long thought to be the underdog models, as the dominant progenitors of normal SNe Ia. Thus the fate of rapidly-accreting Chandrasekhar mass WDs in the single-degenerate channel remains more mysterious then ever. In this talk, I will clarify the nature of ignition in Chandrasekhar-mass single-degenerate SNe Ia and demonstrate that the overwhelming majority of ignition events within Chandrasekhar-mass WDs in the single-degenerate channel are generally expected to be buoyancy-driven, and consequently lack a vigorous deflagration phase. I will show, using both analytic criteria and multidimensional numerical simulations, that the single-degenerate channel is inherently stochastic and leads to a variety of outcomes from failed SN 2002cx-like events through overluminous SN 1991T-like events. I will conclude with a range of observational tests which will either support or strongly constrain the single-degenerate scenario. [Preview Abstract] |
Saturday, November 7, 2015 8:42AM - 8:54AM |
B1.00002: A Framework for the Energy Spectrum of Primary Cosmic Rays. David W. Kraft Although cosmic rays have been the subject of intense observation and research efforts since their discovery in 1912, there remain unanswered questions of a fundamental nature. Among these is the origin of the declining power laws which characterize the energy spectrum of primary cosmic rays, i.e., of nucleons incident upon the Earth's atmosphere. Their flux observed over more than fourteen orders of magnitude of energy varies with energy as $E^{-\gamma }$in which the exponent assumes values between 2.5 and 3.2. We provide herein a framework to account for these values. Our procedure assumes a top-down model in which cosmic rays are produced by the degradation of the energy of initially high-energy particles via collisions with nucleons. It employs the nucleons' kinetic temperature $T$ and introduces a factor $T^{-m}$ to damp the number of collisions that result in high temperatures. It is the presence of the index $m$ which can provide the observed values of $\gamma $. [Preview Abstract] |
Saturday, November 7, 2015 8:54AM - 9:06AM |
B1.00003: Factor Orderings, Vacuum Energy, and Topology in 2-D Quantum Gravity Dhruv Patel The Polyakov action is a generalization of the arc length problem for the motion of free particles along length-minimizing curves. It uses the idea of embedded minimal surfaces to construct a completely geometric model of 2-D gravity. The Polyakov action can be reduced to a quantum mechanics problem by imposing proper time gauge. In this talk, I will construct a propagator for the 2-D gravity quantum mechanical Hamiltonian considering factor ordering ambiguity. I will also discuss some topological issues related to the reduction of the Polyakov action to a finite dimensional action. [Preview Abstract] |
Saturday, November 7, 2015 9:06AM - 9:18AM |
B1.00004: The evolution of galaxies and black holes in the era of precision cosmology Ryan Hickox With the initial parameters of the Universe now exceptionally well constrained, there has been remarkable recent progress in understanding how its components (dark matter halos, galaxies, and black holes) form and evolve over cosmic time. I will give a brief overview of the current picture of galaxy evolution as developed through large-scale surveys, observations of the distant Universe, and cosmological simulations. I will focus on the connections between galaxies and their central supermassive black holes, and will discuss some recent observational advances in this area as well as some current outstanding problems. In particular, I will highlight recent results about the importance of "flickering" nuclear activity in galaxies, and speculate that all star-forming galaxies may host actively growing supermassive black holes. [Preview Abstract] |
Saturday, November 7, 2015 9:18AM - 9:30AM |
B1.00005: Factor ordering and path integral measures in 2d quantum gravity and quantum cosmology Rachel Maitra A central problem in canonical quantum gravity is the selection, from among infinitely many possibilities, of an appropriate ordering for noncommuting factors in the kinetic term of the Wheeler-DeWitt operator. The same issue presents itself in a path integral approach when one seeks to define a measure on a space of histories. This talk examines these two linked problems in the simpler contexts of 2d quantum gravity and quantum cosmology, where the configuration space becomes finite dimensional and the issues quantum mechanical rather than quantum field theoretic. For a range of factor orderings, we investigate the implied domain of physical states for the Hamiltonian, solutions to the Wheeler-DeWitt equation, and associated path integral expressions. [Preview Abstract] |
Saturday, November 7, 2015 9:30AM - 9:42AM |
B1.00006: Laboratory Simulation of Stellar Intensity Interferometry Patricia Bolan, Abigail McBride, Nolan Matthews, David Kieda The field of Stellar Intensity Interferometry (SII) uses large telescopes to track intensity fluctuations from distant stars to create high resolution images of the source. The goal of this project was to explore SII methods using a simulated pseudo-thermal light source in the laboratory. A dynamically scattered laser beam is shone through pinholes, mimicking starlight. This light hits two photomultiplier tubes (PMTs), which convert photons to amplified current, and the spatial cross-correlation between the two signals is recorded over a multitude of baselines by moving one of the PMTs at gradual intervals. Different sized pinholes were experimented with, modelling both single and binary star systems. Information about the sources was retrieved through analysis of cross-correlation data. In the future, this method can be taken to a telescope array, providing a technique to see fine details and brightness distributions in stellar bodies that have been previously unobserved. [Preview Abstract] |
Saturday, November 7, 2015 9:42AM - 9:54AM |
B1.00007: Transverse Structure of the Nucleon in SIDIS Saman Bastami, Peter Schweitzer Transverse momentum-dependent parton distribution functions (TMDs) provide a powerful tool to probe the internal quark-gluon structure beyond what is known about the longitudinal momentum distributions of quarks and gluons from collinear parton distribution functions. Information on TMDs can be accessed in semi-inclusive deep-inelastic scattering and similar reactions, and will shed new light on the transverse structure of the nucleon including transverse spin and transverse momentum distributions. In this talk we discuss the description of SIDIS data in the so-called Wandzura-Wilczek-type approximation. Our predictions will be tested in future experiments at Jefferson Lab. [Preview Abstract] |
Saturday, November 7, 2015 9:54AM - 10:06AM |
B1.00008: Nuclear Lasers as Particle Producers and Accelerators Richard Kriske Nobel gas Lasers such as He-Ne, Ar, Ar-Kr, hold in them a secret. There is a mystery as to how one can take a lower energy photon and produce a higher energy photon, from pumping, electron exchange or particle collision. Consider what would happen if you used the nearby Nuclear states between Xe-135, Xe-136 and Cs 135. At first glance it has the look and feel of yet another Noble Gas Laser. The difference is that it uses Neutron states within the Nucleus. A Gamma or X-ray Laser can be used as the optical pump in order to keep the Neutrons in a state of superposition between the gases. The Neutrons would be emitted with a modulated Gamma or X-ray photon. In essence it may be possible to have a totally new type of Laser---This author calls them "Matter Lasers", where a lower energy photon with fewer Quantum Numbers would be used with a Noble Gas to produce a particle beam with higher energy and more Quantum Numbers. Of course this matter producing beam is already portended by the workings of current Lasers. It may be possible to replace cumbersome particle accelerators with this type of Laser, to make mass from energy, via a Neutron Gas. This would be a great technological advance in Rocket Propulsion as well; low mass photon to high mass particle, such as a Higgs. [Preview Abstract] |
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