Bulletin of the American Physical Society
2006 73rd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 9–11, 2006; Williamsburg, Virginia
Session HB: Gravity/Astrophysics |
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Chair: Guido Mueller, University of Florida Room: Williamsburg Hospitality House Jamestown |
Friday, November 10, 2006 10:15AM - 10:39AM |
HB.00001: The LISA benchtop simulator at the University of Florida James Thorpe, Rachel Cruz, Sridhar Guntaka, Guido Mueller The Laser Interferometer Space Antenna (LISA) is a joint NASA-ESA mission to detect gravitational radiation in space. The detector is designed to see gravitational waves from various exciting sources in the frequency range of 3$\times $10$^{-5}$ to 1 Hz. LISA consists of three spacecraft forming a triangle with 5$\times $10$^{9}$ m long arms. The spacecraft house proof masses and act to shield the proof masses from external forces so that they act as freely-falling test particles of the gravitational radiation. Laser interferometry is used to monitor the distance between proof masses on different spacecraft and will be designed to see variations on the order of 10 pm. Pre-stabilization, arm-locking, and time delay interferometry (TDI) will be employed to meet this sensitivity. At the University of Florida, we are developing an experimental LISA simulator to test aspects of LISA interferometry. The foundation of the simulator is a pair of cavity-stabilized lasers that provide realistic, LISA-like phase noise for our measurements. The light travel time between spacecraft is recreated in the lab by use of an electronic phase delay technique. Initial tests of the simulator have focused on phasemeter implementation, first-generation TDI, and arm-locking. We will present results from these experiments as well as discuss current and future upgrades in the effort to make the LISA simulator as realistic as possible. [Preview Abstract] |
Friday, November 10, 2006 10:39AM - 10:51AM |
HB.00002: Probing the Universe on the Largest Possible Scales with Remote Cosmic Microwave Background Quadrupole Observations Emory Bunn Observations of cosmic microwave background (CMB) anisotropy suggest the possibility that the Universe is not statistically isotropic --- that is, that it has a preferred direction --- but the statistical significance of these claims is controversial. To settle the question we need an independent data set probing the same physical scales. Scattering of CMB radiation in galaxy clusters may provide the information we need: it produces a polarization signal proportional to the CMB quadrupole anisotropy at the cluster's location and look- back time, thus probing ultra-large-scale perturbations. I will present calculations of the number of independent modes that can be obtained from such a ``remote quadrupole'' survey, along with the length scales probed by these modes. In a sparse survey of a large area of sky, the largest-scale modes probe length scales comparable to the large- angle CMB anisotropy but with much narrower Fourier-space window functions. The formalism presented here is also useful for analyzing smaller-scale surveys to probe the late integrated Sachs-Wolfe effect and hence the properties of dark energy. [Preview Abstract] |
Friday, November 10, 2006 10:51AM - 11:03AM |
HB.00003: Search for Giant Pulses in High Edot Pulsars Melissa Ilardo In order to investigate a possible correlation between the Edot of a pulsar and the presence of giant pulses, we made observations of pulsars J1930+1852, B1951+32 and J1913+1011 using the WAPP (Wideband Arecibo Pulsar Processor) at the Arecibo Observatory. We chose these pulsars because they possess high Edots, a characteristic shared by the Crab Pulsar, PSR B1937+21, PSR B0540-69 and B1821-24; four of the few currently known giant pulse emitters. Although no giant pulses were positively identified, PSR J1913+1011 showed enough possible evidence to warrant further research. [Preview Abstract] |
Friday, November 10, 2006 11:03AM - 11:15AM |
HB.00004: Modeling the Galaxy's Rotation Curve Daniel Serrano, J. Hasbun The orbital speed of material in the Galaxy does not behave according to Kepler's 3$^{rd}$ law. This has led astronomers to postulate the existence of Dark Matter. Dark Matter is a form of missing mass; it is basically undetected matter in the universe that is under luminous and probably quite different from ordinary matter (Comins and Kaufmann 2005). In this paper we investigate the modeling of the Galaxy's rotation curve. Our models make use of a modified version of Newton's universal law of gravitation. The idea is that we employ Gauss' Law as applied to gravitation; i.e., $\oint {g\cdot \hat {n}d\vec {A}=-4\pi G\int {\rho d\tau } } $, to obtain expressions for the orbital velocity of the material within the galaxy. While this formula is capable of obtaining Newton's universal law of gravitation for constant density$\rho $, it is also flexible in that the density can be a variable. The variability in the density $\rho $ is studied to investigate the fluctuations present in the experimental rotation curve. Six models are presented for this purpose: (a) The Exponential model, (b) the Gaussian model, (c) the Spiral model, (d) the Exponential-Cosine model, (e) the Gaussian-Cosine model, and (f) the Harmonic model. The models are listed in order of increasing improvement when compared to the observational curve. [Preview Abstract] |
Friday, November 10, 2006 11:15AM - 11:27AM |
HB.00005: Influence of collapsing matter on the enveloping expanding universe Abdul Choudhury Using a collapsing matter model at the center of an expanding universe as described by Weinberg [1] we assume a special type of generated pressure [2]. This pressure transmits into the surrounding expanding universe. Under certain restriction the ensuing Hubble parameter is positive. The deacceleration parameter fluctuates with time, indicating that the universe accelerates for certain time and decelerates for other time intervals. \newline \newline [1] S. Weinberg : Gravitation and Cosmology, J. Wiley \& Sons, Inc. New York (1972) page 342. \newline [2] A. L. Choudhury, Hadronic J., 23, 581 (2000). [Preview Abstract] |
Friday, November 10, 2006 11:27AM - 11:39AM |
HB.00006: AdS/CFT Correspondence and Heavy Ion Collisions James Alsup, Chad Middleton, George Siopsis We study perturbations of the gravity dual to a perfect fluid model recently found by Janik and Perschanski. We solve the Einstein equations in the bulk Anti-de Sitter space for a metric ansatz which includes off-diagonal terms. Through holographic renormalization, we show that these terms give rise to heat conduction in the corresponding gauge theory on the boundary. Our results might be relevant to understanding experimental results at heavy ion colliders such as RHIC. [Preview Abstract] |
Friday, November 10, 2006 11:39AM - 11:51AM |
HB.00007: $E_6$ grand-unification for a Dark Energy model Paola Mosconi, P.Q. Hung The unification of a recently proposed model for Dark Energy and Dark matter [1], based on an unbroken gauge group $SU(2)_Z$, with the Standard model (SM) is presented. The unifying group is $E_6$ and the symmetry breaking pattern takes the unusual route $E_6\to SU(2)_Z \otimes SU(6)\to SU(2)_Z \otimes SU(3)_c \otimes SU(3)_L \otimes U(1)_6\to SU(2)_Z \otimes SU(3)_c \otimes SU(2)_L \otimes U(1)_{3}\otimes U(1)_6\to SU(2)_Z \otimes SM$. We find that the SM couplings converge into $SU(6)$ at a mass scale $\ord(2 \times 10^{15}\gev)$, corresponding to a proton mean lifetime $\tau_p\sim 9 \times 10^{32}\textrm{yr}$, consistent with the actual lower bound, while the $E_6$ grand-unification occurs below the Planck scale. This scenario implies the existence of heavy mirror fermions with masses $\ord(250 \gev)$. \newline \newline [1] P. Q. Hung, hep-ph/0504060; \textit{ibid.}, Nucl. Phys. B {\textbf{747}}, 55 (2006). [Preview Abstract] |
Friday, November 10, 2006 11:51AM - 12:03PM |
HB.00008: A Classical Complex 4-Wave Foundation of the Cosmic-Quantum Mechanism Mart Gibson A model of a fundamental $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $ spin quantum as a simple harmonic oscillation of an expanding 3-space of variable inertial density and resonant frequency in an underlying 4-continuum is developed. Expansion provides a mechanical analogue of an EMF which drives the neutral quantum. Absent inertial confinement, a differential decrease in inertial density creates a discontinuity, inducing a decrease in frequency to that of the proton, with transmission of the electron. Quantum gravity arises as the derivative of the wave force with respect to the expansion tension stress, and the Planck area as the derivative of the fundamental cross-sectional scale with respect to a change in stress. An exponential Hubble rate is coupled with the differential wave force and thereby beta decay. The nature of matter and anti-matter as inductive and capacitive states, respectively, is straightforward. A quantum mechanism, with animation, modeling the above is developed with the derivation of an inertial constant, $t(tav)=\hbar /c$. A matrix of the wave symmetries, functions, invariants, and their couplings is examined, clearly showing the relationship of the electromagnetic and gravitational interactions. [Preview Abstract] |
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