Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session L6: Tests of General Relativity and Gravitation |
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Sponsoring Units: GGR Chair: Nicholas Yunes, Montana State University Room: Embassy C |
Sunday, April 1, 2012 3:30PM - 4:06PM |
L6.00001: Probing the Strong-Field with Compact Binaries Invited Speaker: Nicolas Yunes Einstein's theory of General Relativity has passed all tests to date in the quasi-stationary weak-field, where the gravitational force is weak and velocities are small. In the near future, new electromagnetic and gravitational wave data will allow us to test Einstein's theory to new, exciting levels in the strong-field regime, such as in the neighborhood of black holes and neutron stars or when such compact binaries coalesce. In this talk, I will review recent work aimed at understanding what types of new General Relativity tests can be performed in the strong field, using gravitational wave instruments and electromagnetic observations. [Preview Abstract] |
Sunday, April 1, 2012 4:06PM - 4:18PM |
L6.00002: Towards a practical approach for testing General Relativity with gravitational wave detections Laura Sampson, Neil Cornish, Nicolas Yunes The detection of gravitational waves in the advanced detector era will allow us to perform the first tests Einsteins's theory of gravity in the dynamical, strong-field regime. The parameterized post-Einsteinian waveform model provides a framework in which to develop powerful tests that can be applied to the signals from compact binary systems. We describe a practical implementation of such a testing scheme that optimally combines the information from multiple detections. [Preview Abstract] |
Sunday, April 1, 2012 4:18PM - 4:30PM |
L6.00003: Modified gravity and scalar fields: where should we look? Emanuele Berti I will discuss how strong-field modifications of Einstein's general relativity can affect the structure of compact stars. I will also argue that generic scalar-tensor theories may have characteristic signatures in the gravitational-wave signal from compact binaries, that could be observable by Earth- and space-based gravitational-wave detectors. [Preview Abstract] |
Sunday, April 1, 2012 4:30PM - 4:42PM |
L6.00004: ABSTRACT WITHDRAWN |
Sunday, April 1, 2012 4:42PM - 4:54PM |
L6.00005: Correlations Between Cosmological Parameters and Modified Gravity Parameters when Testing Gravity at Cosmological Scales Jason Dossett, Mustapha Ishak, Jacob Moldenhauer Motivated not only by the pressing question of cosmic acceleration but also by the proposals of some extensions to general relativity that would manifest themselves at large scales of distance, the testing of general relativity at cosmological scales has become a possible and timely endeavor. Here, we analyze correlations between modified gravity growth parameters and some core cosmological parameters using the latest cosmological data sets. We use known functional and binning approaches, and a new hybrid approach to evolve the modified gravity parameters in redshift (time) and scale. The hybrid approach combines a binned redshift dependence and a smooth evolution in scale avoiding a jump in the matter power spectrum. The formalism developed to test the consistency of current and future data with general relativity is implemented in a publicly available package \texttt{ISiTGR} ({\it Integrated Software in Testing General Relativity}). We find for all evolution methods that modified gravity parameters are significantly correlated with $\sigma_8$ and mildly correlated with $\Omega_m$. These degeneracies will need to be taken into consideration when using future high precision data. [Preview Abstract] |
Sunday, April 1, 2012 4:54PM - 5:06PM |
L6.00006: Experimental search for violations of Newtonian gravity at short ranges Josh Long, Simon Kelly, Evan Weisman, Trevor Leslie, Andrew Peckat We report on our ongoing experimental search for deviations from the Newtonian gravitational inverse-square law at short ranges (50 microns). This experiment permits us to place constraints on theories predicting new forces at sub-millimeter range, including models with compact extra dimensions and gravitationally-coupled scalar fields. The experiment is performed by measuring the force between a planar source mass oscillating at a frequency (1 kHz) tuned to one of the mode frequencies of a planar detector mass. Electrostatic and acoustic background forces are mitigated by separating the source and detector masses with a conducting, 10 micron-thick Copper-Beryllium membrane stiffened by stretching, while the Newtonian background is minimized with the nominally null planar test mass geometry. We search for a signal above the limiting detector thermal noise after integration times on the order of 1 day. [Preview Abstract] |
Sunday, April 1, 2012 5:06PM - 5:18PM |
L6.00007: Test Mass Development for Sub-Millimeter Searches for New Forces of Nature Evan Weisman, Simon Kelley, Hans-Otto Meyer, Andrew Pecket, Josh Long Experimental searches for new forces of nature at short range have attracted a great deal of attention over the last decade. We describe test mass development for two new force searches below 1 mm. Both experiments use 1 kHz mechanical oscillators as test masses with a stiff conducting shield in between them to suppress backgrounds, a technique showing promise for probing exceptionally small distances and operation at the limit of instrumental thermal noise. For one experiment, which will be operated at cryogenic temperature to further reduce the thermal noise, pure metallic test masses have been shown to have mechanical quality factors large enough so that the measurement will be dominated by the Newtonian backgrounds, leading to studies with plated silicon masses. In addition, a currently operational room temperature experiment is being modified to test for spin-dependent interactions by applying spin-polarized materials to the test mass surfaces. We report investigations of our initial candidate material, a ferrimagnetic DyFe compound used in previous torsion-pendulum experiments, that exhibits orbital compensation of the magnetism associated with the intrinsic electron spins. [Preview Abstract] |
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