Bulletin of the American Physical Society
2014 Annual Meeting of the Mid-Atlantic Section of the APS
Volume 59, Number 9
Friday–Sunday, October 3–5, 2014; University Park, Pennsylvania
Session C3: Gravitation and Cosmology I |
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Chair: Wolfgang Wieland, Pennsylvania State University Room: Life Sciences Building 005 |
Saturday, October 4, 2014 10:30AM - 11:06AM |
C3.00001: From cosmological observations to fundamental physics: past, present, and future Invited Speaker: Cora Dvorkin . [Preview Abstract] |
Saturday, October 4, 2014 11:06AM - 11:18AM |
C3.00002: Searching for Gravitational Waves from the Coalescence of High Mass Black Hole Binaries Sophia Xiao We search for gravitational waves from the coalescence (inspiral, merger and ringdown) of binary black holes with data from the Laser Interferometer Gravitational-Wave Observatory (LIGO). Provided with well-described waveform models from General Relativity, matched filtering is employed in the GSTLAL analysis pipeline as the optimal detection technique for weak signals in Gaussian noise. The GSTLAL analysis pipeline filters data with waveform template banks, identifies triggers with SNR greater than 4, forms coincident triggers between multiple detectors in the LIGO Scientific Collaboration, and attempts to optimally separate signal from detector background noise fluctuations using a Chi-squared test. We run high-statistics simulations of binary merger waveforms injected into LIGO recolored S6 data to evaluate the pipeline search sensitivity, to test the readiness of the pipeline for Advanced LIGO. With Advanced LIGO fully in operation by 2015 and the upgraded analysis pipelines, the expected detection rate is increased to as much as 100 events/year or more as compared to 0.01-1 events/year in Initial LIGO. Our work will make it possible to detect gravitational waves from binary black hole coalescence in Advanced LIGO data with high confidence. [Preview Abstract] |
Saturday, October 4, 2014 11:18AM - 11:30AM |
C3.00003: Supernova Constraints on Modified Theories of Gravity Nathan Prins, James Overduin, Joohan Lee Most attempts to unify gravitation with the standard model of particle physics involve new fields and/or additional (usually compact) dimensions. The dynamics of these compact extra dimensions can, however, act back on the dynamics of macroscopic space and time. We investigate a particular class of models with $n$ compact dimensions plus a scalar field with negative kinetic energy (``phantom''), and show that they are strongly disfavored by recent data on the magnitudes of Type Ia supernovae. [Preview Abstract] |
Saturday, October 4, 2014 11:30AM - 11:42AM |
C3.00004: Asympotics with a positive cosmological constant I Aruna Kesavan, Abhay Ashtekar, Beatrice Bonga Since observations to date imply that our universe has a positive cosmological constant, one needs an extension of the theory of isolated systems and gravitational radiation in full general relativity from asymptotically flat to asymptotically de Sitter space-times. If one mimics the boundary conditions used in asymptotically anti-de Sitter context, then one concludes that the asymptotic symmetry group is the de Sitter group. However, these conditions severely restrict radiation and in fact rule out non-zero flux of energy, momentum and angular momentum carried by gravitational waves. Therefore, such a definition of asymptotically de Sitter space-times is uninteresting beyond non-radiative space-times. A new proposal is expounded to remedy the situation for non-stationary space-times. [Preview Abstract] |
Saturday, October 4, 2014 11:42AM - 11:54AM |
C3.00005: Asymptotics with a positive cosmological constant II: Illustration with linear fields on de Sitter space-time Beatrice Bonga, Abhay Ashtekar, Aruna Kesavan The framework that allows the study of isolated systems is well-developed for space-times with a vanishing cosmological constant $\Lambda$ and it lies at the foundation of research in diverse areas in gravitational physics. However, the standard extension of this framework to space-times with a positive $\Lambda$ fails for non-stationary space-times. Here, I will outline a new proposal that does allow the study of isolated systems with $\Lambda>0$ in a physically meaningful manner and has the additional benefit of providing a natural comparison with asymptotically flat space-times. This proposal is illustrated by calculations with test fields in de Sitter space-time. The results are contrasted with test fields in Minkowski space-time. It is expected that the results for test fields will share many features with gravitating systems. The linear analysis provides a first step to study the errors one makes by assuming $\Lambda=0$ when studying general relativistic gravitating systems. [Preview Abstract] |
Saturday, October 4, 2014 11:54AM - 12:06PM |
C3.00006: Derivation of the Biot-Savart Law from Coulomb's Law and Implications for Gravity Daniel Zile, James Overduin We explore links between classical electromagnetism and general relativity in the low-velocity, weak-field limit. We confirm that it is possible to derive the Biot-Savart law for magnetism from Coulomb's law for electrostatics by moving to a boosted frame and applying the force transformation law from special relativity. We then apply the same transformation to Newton's law of gravitation, obtaining a gravitational analog of the magnetic field with units of spin. This field turns out to be two-thirds of the geodetic precession predicted by general relativity theory, a prediction that has recently been verified experimentally by the Gravity Probe B satellite. We discuss some physical interpretations and implications of this result. [Preview Abstract] |
Saturday, October 4, 2014 12:06PM - 12:18PM |
C3.00007: Characteristics of Gravitational and Electromagnetic Radiation Maria Babiuc Both gravitational and electromagnetic radiation travel along light rays, which are principal null directions in space-time. They are characteristic surfaces of Einstein and Maxwell equations. We start with the coupled Einstein-Maxwell equations together with the Maxwell equations, for a space-time given by the null Bondi-Sachs line element, and a null electromagnetic gauge field. In this characteristic framework, we deduce analytical expressions describing the gravitational waves and the electromagnetic counterparts at infinity, as well as the nonlinear effects of the interaction between them, such as radiation memory. The source of gravitational and electromagnetic radiation is treated as a black box, and therefore the approach is very flexible, with potentially large applicability. [Preview Abstract] |
Saturday, October 4, 2014 12:18PM - 12:30PM |
C3.00008: The emergence of spacetime from quantum gravity Marc Geiller I will present some recent ideas and developments in non-perturbative quantum gravity, and illustrate how loop gravity and spin foam models could possibly describe the emergence of continuum spacetime from discrete elementary building blocks. [Preview Abstract] |
Saturday, October 4, 2014 12:30PM - 12:42PM |
C3.00009: Cosmological Coincidence without Fine Tunning Joohan Lee, James Overduin, Tae Hoon Lee, Phillial Oh We present a simple cosmological model in which a single, non-minimally coupled scalar field with a quartic potential and a non-canonical kinetic term is responsible for inflation at early times and acceleration at late times. No fine tuning is needed to explain why the present density of dark energy is comparable to that of pressureless matter. Dark energy in this theory originates in the potential energy of the scalar field, which in turn is sourced by the trace of the energy-momentum tensor. This becomes significant when the bulk of the matter content of the universe has decoupled from radiation and become fully non-relativistic, so that $\phi\propto\rho_m^{1/3}\propto\rho_{m,0}^{1/3}(a_0/a)\sim(10^{-120})^{1/3}(10^{10})\sim10^{-30}$ and $V\sim\phi^4\sim10^{-120}$ in Planck units, as observed. [Preview Abstract] |
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