Bulletin of the American Physical Society
14th Annual Meeting of the Northwest Section of the APS
Volume 57, Number 7
Thursday–Saturday, October 18–20, 2012; Vancouver, British Columbia, Canada
Session C1: Astronomy, Cosmology, and Gravity |
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Chair: Sukanta Bose, Washington State University Room: SFU Harbour Centre 1700 Labatt Hall |
Friday, October 19, 2012 1:30PM - 2:06PM |
C1.00001: Peering through the EoR window with the Murchison Widefield Array Invited Speaker: Miguel Morales Measurement of the spatial distribution of neutral hydrogen via the redshifted 21 cm line promises to transform our knowledge of the Epoch of Reionization (EoR). In my talk I will give an accessible introduction to this new field, discuss how we plan to observe the faint 21 cm fluctuations in the face of strong foregrounds, and show our latest results from prototype and early commissioning observations with the MWA as we start to peer through the EoR window. [Preview Abstract] |
Friday, October 19, 2012 2:06PM - 2:18PM |
C1.00002: Estimates of the Neutrino Dynamics of Black Hole-Neutron Star Mergers M. Brett Deaton, Matthew D. Duez In an attempt to further understand black hole-neutron star systems (BHNS) as potential gamma ray burst central engines we explore the dynamics of BHNS mergers of low mass ratio and high spin. Our simulations include radiative cooling through a leakage approximation. We examine the neutrino signal, the remnant disk dynamics, and the energy deposited by neutrino pair annihilations around the disk. [Preview Abstract] |
Friday, October 19, 2012 2:18PM - 2:30PM |
C1.00003: Status of Advanced LIGO Michael Landry Installation of Advanced LIGO, a second-generation interferometric gravitational wave observatory, began in earnest in October of 2010. Initial LIGO instrumentation was de-installed, vacuum chambers and envelope modified, and the installation of scientific payloads begun. At LIGO Hanford Observatory, optics and suspensions comprising one of two 4km Fabry-Perot arms have been deployed and commissioned, resonating green light in an experiment to test and understand the process of controlling cavity lengths (``lock acquisition''). At LIGO Livingston, cornerstation optic and seismic isolation installation has matured such that the primary infrared laser and a suspended mode cleaner cavity (employed to spacially clean the interferometer input beam) are locked and under commissioning test. In this talk we present the status of Advanced LIGO installation and integration, and sketch the promising future of gravitational wave observation and astronomy. [Preview Abstract] |
Friday, October 19, 2012 2:30PM - 2:42PM |
C1.00004: Real-time Simulation of a Suspended Cavity with the Advanced LIGO Digital Controls System Alexandra Zhdanova LIGO is a collaboration brought together by the goal of detecting gravitational waves sent out by especially massive, quickly-moving objects. An integral part of LIGO's interferometers are the Fabry-Perot cavities in the arms. Modeling them can show us how well we understand the noise in addition to serving as a test of the control system used to keep the interferometer in resonance. While time-domain simulations of the cavity have been done, a real-time model would provide a better comparison point for the noise while accurately simulating the cavity response. This presentation outlines such a real-time model, as well as a comparison between the results of the ``fake'' (or simulated) cavity and the ``real'' cavity. The closer these results are to each other, the more successful we count our model as an accurate representation of the real-life noise and mechanics in a Fabry-Perot cavity. [Preview Abstract] |
Friday, October 19, 2012 2:42PM - 2:54PM |
C1.00005: Heavy Dark Matter and High Energy Cosmic Rays Kyle Lawson Conventional dark matter models assume that the dark matter is composed of new fundamental particles which interact only weakly with visible matter. One alternative to this picture is a model in which the dark matter is actually composed of standard model quarks (or antiquarks) bound into macroscopically large composite objects. If these objects are sufficiently massive they become unobservable due to their correspondingly small number density. For dark matter with very low density experimental searches are limited by detector size rather than sensitivity. I will outline the basic properties of quark nugget dark matter and analyze their interactions with molecules of earth's atmosphere. Depending on the nature of the quark matter involved the total energy deposited can be observably large. In this case the quark nugget will trigger an extensive air shower similar to that initiated by a single ultrahigh energy proton or nucleus. As such, it is possible that large scale cosmic ray experiments are capable of detecting this type of dark matter. A dark matter signal may be seen in both fluorescence and surface detectors as well as in radio detection experiments. I will offer a description of the potential signal in each of these channels and a brief summary of detection potential. [Preview Abstract] |
Friday, October 19, 2012 2:54PM - 3:06PM |
C1.00006: Searching for dark matter axions with ADMX Dmitry Lyapustin Axions are hypothetical elementary particles that may help provide the answer as to why QCD preserves the discrete symmetries P and CP. Light axions also have properties that make them ideal dark-matter candidates. The Axion Dark Matter eXperiment (ADMX) has been at the forefront of the dark-matter axion search for over two decades, and is currently being upgraded to improve its sensitivity to where it will either be able to detect the QCD dark-matter axion, or reject the hypothesis at high confidence. I will motivate the existence of axions, discuss ADMX and its previous results, and highlight the state of the current upgrade. [Preview Abstract] |
Friday, October 19, 2012 3:06PM - 3:18PM |
C1.00007: The ADMX ultra-low noise receiver Christian Boutan Finding axions would finally point to the solution to the ``strong CP problem'' in QCD and uncover the nature of the Mily Way's dark-matter halo. The Axion Dark Matter eXperiment (ADMX) is a sensitive search for such axions. ADMX looks for the exceedingly tiny amount of power that would be released in the very weak conversion of dark-matter axions to photons. The key to the sensitivity of ADMX is a microwave receiver sensitive to sub-yoctowatt electromagnetic power. ADMX is currently being upgraded to a lower noise temperature and a new receiver design that has the sub-Hz spectral resolution necessary for the detection of even exotic non-virialized axion dark-matter halo models. I discuss the simulation nature of the axion signal and the calibration of this receiver using simulated axion signals. [Preview Abstract] |
Friday, October 19, 2012 3:18PM - 3:38PM |
C1.00008: BREAK |
Friday, October 19, 2012 3:38PM - 4:14PM |
C1.00009: Magnetic stars as remote laboratories for magnetic physics Invited Speaker: Jaymie Matthews Understanding the magnetic field of the Sun, its dynamo origin, its evolution with time, and its interactions with the solar corona, solar wind and interstellar medium is important and exciting. But the Sun's field is relatively weak and globally disorganized. There are more massive stars whose magnetic fields are thousands (even tens of thousands) of times stronger, with dipole geometries more reminiscent of the Earth's field than the Sun's. Such fields can help regulate processes like radiative diffusion and gravitational settling in stellar atmospheres, and their Lorentz forces can even modify the spherical harmonics and the frequencies of a star's resonant vibrations. And even in the case of weaker solar-like magnetic fields, there are stars with exoplanets in tight orbits where the planet's magnetospheres is tangled with the star's magnetic field lines, generating activity in the star's atmosphere beneath the planet in its orbit. Examples of all of these types of systems have been studied through ultraprecise time series optical photometry with Canada's space telescope, MOST, often in concert with spectroscopy and spectropolarimetry from earthbound observatories. It'll be hard to cover so much parameter space in only half an hour, but I'll try to give you a glimpse at the surfaces of these stellar magnetic labs, and even a peek inside their normally hidden interiors. [Preview Abstract] |
Friday, October 19, 2012 4:14PM - 4:26PM |
C1.00010: Studies of Galactic Magnetism Jo-Anne Brown Magnetic fields are an important constituent of the interstellar medium, but unlike gas, dust and cosmic rays, they do not radiate, and consequently cannot be observed directly. Instead, observations of the {\it{signatures}} of magnetic fields have allowed researchers to piece together the structure of the magnetic field in our Galaxy and others. In this talk, I will review some of the latest findings in our quest to determine the struture of the magnetic field in our Galaxy, and how this knowledge is shaping our understanding of the origin and evolution of galactic magnetic fields in general. [Preview Abstract] |
Friday, October 19, 2012 4:26PM - 4:38PM |
C1.00011: Cosmological Inflation: Testing Initial Conditions of Inhomogeneous Inflation Fields Auberry Fortuner The cosmological model explains how the expansion of the Universe is determined by the energy density, yet suffers from some limitations that can be overcome only if the Universe began under very specific conditions. The theory of inflation was proposed to solve these problems by introducing a period of rapid expansion in the early Universe. The mechanism that causes inflation is the evolution of a scalar field, which determines the energy density and expansion of the Universe. The evolution of the scalar fields depends on the type of field and the initial conditions we give it. Scalar fields that are flat and smooth generally cause inflation, yet scalar fields that fluctuate may delay or prevent inflation under certain initial conditions by introducing an additional energy density. Our research investigated the range of initial conditions for two models of inhomogeneous scalar fields that allow inflation to occur. The equation of motion of the scalar fields were solved numerically allowing us to determine the amount of expansion that results from each set of initial conditions, and whether or not inflation occurs. [Preview Abstract] |
Friday, October 19, 2012 4:38PM - 4:50PM |
C1.00012: Decay of false vacuum and solar system test of f(R) gravity Jun-Qi Guo, Andrei V. Frolov The scenario of false vacuum decay can describe the nucleation processes of statistical physics. Historically it was also used to build the early theory of inflation. In this talk, we will discuss another application: solar system test of f(R) gravity. f(R) gravity is to interpret the current accelerating expansion of the universe. In solar system, f(R) gravity is required to reduce to general relativity so as to meet the observations. In the ``Chameleon mechanism,'' the scalar field, f'=df/dR, might couple to the matter density both inside and outside of the Sun. Therefore, the field, f', can be regarded to decay from the false vacuum of an effective potential to the true one. We find that, 1) the thin-wall approximation condition derived in the scenario of false vacuum decay can be written in a more intuitive way; 2) compared to the thin-shell condition obtained in Chameleon mechanism, the thin-wall approximation condition is the more proper one for an f(R) model to meet the solar system test. The numerical solutions to the equation of motion of f' for RlnR and Hu-Sawicki models verify the thin-wall approximation condition, and also explain the difficulties that the RlnR model faces in the solar system test. [Preview Abstract] |
Friday, October 19, 2012 4:50PM - 5:02PM |
C1.00013: A Breathing mode for Compactifications Bret Underwood Reducing a higher dimensional theory to a 4-dimensional effective theory results in a number of scalar fields describing, for instance, fluctuations of higher dimensional scalar fields (dilaton) or the volume of the compact space (volume modulus). But the fields in the effective theory must be constructed with care: artifacts from the higher dimensions, such as higher dimensional diffeomorphisms and constraint equations, can affect the identification of the degrees of freedom. The effective theory including these effects resembles in many ways cosmological perturbation theory. In this talk I will briefly outline how constraints and diffeomorphisms generically lead the dilaton and volume modulus to combine into a single degree of freedom in the effective theory, the ``breathing mode.'' [Preview Abstract] |
Friday, October 19, 2012 5:02PM - 5:14PM |
C1.00014: Statistical mechanics of graph models and their implications for emergent manifolds Si Chen, Steven Plotkin Inspired by ``quantum graphity'' models for spacetime, a statistical model of graphs is proposed to explore possible realizations of emergent manifolds. Graphs with a given number of vertices and edges are considered, with a Hamiltonian that favors graphs with near-constant valency and local rotational symmetry. The ratio of vertices to edges controls the dimensionality of the emergent manifold. The model is simulated numerically in the canonical ensemble for a given vertex to edge ratio, where it is found that the low energy states are almost triangulations of two dimensional manifolds. The resulting manifold shows intricate topological structures in a higher dimensional embedding space. The transition is first order, underlying the difficulty of graph models in describing criticality that is independent of the details of the underlying graph. A further perplexing phenomenon is that the entropy of the graphs are super-extensive, a fact known since Erd\"os, which results in a transition temperature of zero in the limit of infinite system size. Aside from a finite-universe as a possible solution, long-range interactions between vertices also resolve the problem and restore a non-zero transition temperature. [Preview Abstract] |
Friday, October 19, 2012 5:14PM - 5:26PM |
C1.00015: The Photon may have mass Richard Kriske The argument for a particle having mass is now days predicated on a Quantum Mechanics. The argument involves the distance that a particular force can be felt, and in the case of the Photon that should be infinity, and if it is infinity then the mass of the Photon has to be zero. This author has some doubts about the distance the Electomagnetic Force can be felt. This author has previously stated that if the Universe has a Horizon wherein there is a three space embedded in four dimensions, where time is perpendicular to the three space dimensions, then if there is curvature, like the curvature of the Earth, then one should see time tilt backward away from the observer at the Horizon (just as a large tower would tilt away from the observer if it where on the other side of an ocean for instance-on the Earth's surface). If this tilting does take place (if Space-Time is not flat, but positively curved), then the Photon redshifts in every direction even if Space-Time is not expanding. This redshift limits the distance of the Electromagnetic Field, and therefore the Photon should have rest mass, as the Horizon acts as a boundary for each observer, but may not be the actual size of Infinity, the Universe may go on for a large distance beyond the Horizon. [Preview Abstract] |
Friday, October 19, 2012 5:26PM - 5:38PM |
C1.00016: Gravity Driven Universe: Energy from a Unified Field Roy Masters One way or another, whether push or pull, we know for sure that gravity is omnidirectional with identical mathematics. With PULL, gravity can be seen as as a property of matter. If so something is wrong. The Moon, lifting the tides twice-daily, should have fallen into orbital decay, with Earth having pulled it down eons ago. It is puzzling that physicists are not troubled by the fact that the Moon not only insists on forever lifting the tides, but, adding insult to injury, \textit{keeps moving it about 4 cm further away} from Earth each year. Now if instead, we consider gravity as driven by an omnidirectional pressure--a PUSH force, another possibility arises. We can consider that it is mysteriously infusing energy into the Earth-Moon system, sustaining the Moon's orbit with the appearance of raising the tides and actually pushing it away from Earth. Here we can show push and pull, while being identical in their mathematics, have different outcomes. With push, gravity is a property of the universe. If this is true, then gravitation is flowing from an everlasting source, and the Earth/Moon system is one example of many other vacuum energy machines in the universe. [Preview Abstract] |
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