Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session S10: Equivalence Principle and Precision Gravity Tests |
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Sponsoring Units: GGR GPMFC Chair: Stephan Schlamminger, University of Washington Room: Maryland B |
Monday, February 15, 2010 3:30PM - 3:42PM |
S10.00001: Testing gravity at scales below 100 microns Charles Hagedorn, Matthew Turner, Stephan Schlamminger, Jens Gundlach Gravity and the standard model are mathematically incompatible. If there exists a theory that unifies them, then, at some length scale, one or both of them must be modified. A number of contemporary theories of the standard model and cosmology suggest that this scale may be as large as 100 microns. As further motivation, the observed dark energy density, when converted to a length, is 86 microns. We have constructed a null experiment using a new plate geometry torsion balance to test gravity, at and below gravitational strength, to scales of 50 microns and smaller. We will present preliminary results. [Preview Abstract] |
Monday, February 15, 2010 3:42PM - 3:54PM |
S10.00002: Short Range Test of the Gravitational Inverse Square Law using the Fourier Bessel Torsion Pendulum Ted Cook, Eric Adelberger, Blayne Heckel, Erik Swanson For this experiment, we removed pie shaped wedges from 50 micron thick tungsten foils to create 120-fold rotationally symmetric attractor and detector masses. The detector mass is hung from a thin tungsten fiber. The attractor mass is rotated continuously beneath it, providing a gravitational drive signal at 120 times the rotational frequency which is recorded via an autocollimator. Comparing the angular deflection of the detector to a precise Newtonian calculation, we are able to place new limits on range-dependent, non-Newtonian physics below 50 microns. [Preview Abstract] |
Monday, February 15, 2010 3:54PM - 4:06PM |
S10.00003: Rotating Torsion Balance Tests of the Equivalence Principle Todd Wagner, Stephan Schlamminger, Jens Gundlach We present current results from tests of the equivalence principle using a rotating torsion balance. Test bodies made from different materials are arranged in a composition dipole and installed on a torsion pendulum. The torsion pendulum is mounted on a turntable that rotates with constant angular velocity. Test body pairs of Be-Ti, Be-Al and test bodies that mimic the earth's and moon's compositions were used. Results are presented with limits using the earth and astrophysical objects as sources for a hypothetical equivalence principle violation. [Preview Abstract] |
Monday, February 15, 2010 4:06PM - 4:18PM |
S10.00004: ABSTRACT WITHDRAWN |
Monday, February 15, 2010 4:18PM - 4:30PM |
S10.00005: A 10 minute test of the weak equivalence principle Robert Reasenberg, Eiichi Hirose, Enrico Lorenzini, Biju Patla, James Phillips, Eugeniu Popescu, Emanuele Rocco, Rajesh Thapa We are developing a payload for detecting a possible violation of the weak equivalence principle while on a sounding rocket's free-fall trajectory. We estimate an uncertainty of $\sigma (\eta )=10^{-16}$ from a single night-time flight. A quick experiment with this accuracy is possible because: 1) The principal measurement is by a laser gauge that has a projected measurement uncertainty of 0.1 pm$/\sqrt {Hz} $; 2) The thermal environment is stable; 3) Payload inversions cancel most systematic error and; 4) The test masses are in unrestrained free fall. I will provide an overview of the project with an emphasis on the features that enable a quick experiment. [Preview Abstract] |
Monday, February 15, 2010 4:30PM - 4:42PM |
S10.00006: SR-POEM requirements for spurious acceleration reduction Biju Patla, Enrico Lorenzini, James Phillips, Robert Reasenberg SR-POEM is a payload we are developing for detecting a possible violation of the weak equivalence principle (WEP) while on a free-fall trajectory provided by a sounding rocket. In the experiment, two test mass assemblies will be allowed to free fall during 8 drops of 40s each. The drops will be separated by payload inversions. We discuss the various sources of spurious test-mass accelerations, emphasizing those that could mimic a WEP violation signal. The studies carried out thus far indicate that the mission uncertainty requirement of $\sigma $ ($\Delta $g/g) $<$ 10$^{-16}$ can be achieved with the inversions, which cancel most of the systematic errors. We address those errors that do not cancel and suggest approaches to control them. Spurious accelerations arise, for example, from the gravity due to the payload mass distribution and variation of surface potential on the test masses and nearby electrodes. We also present the results of detailed calculations which allow us to constrain most of the spurious accelerations within acceptable limits during the measurement phase. Systematic errors due to attitude control and flight dynamics will be examined briefly. [Preview Abstract] |
Monday, February 15, 2010 4:42PM - 4:54PM |
S10.00007: Sub-picometer Laser Distance Gauge for SR-POEM and Astronomical Instruments James D. Phillips, Robert D. Reasenberg We report on a Semiconductor Laser version of the Tracking Frequency laser distance Gauge (SL-TFG). It will be the sensor for SR-POEM, a test of the weak equivalence principle with $\sigma (\eta )<10^{-16}$, and for optical trusses in segmented- and distributed-aperture spaceborne astronomical instruments. The TFG locks a laser to the Measurement Interferometer (MI). This architecture gives it substantial advantages over the traditional precision instrument, the heterodyne phase gauge. The TFG is free of an important source of cyclic bias. Its readout is a radio frequency derived from an optical heterodyne, not an RF phase. Absolute distance can be measured with little or no additional hardware. We report on tests yielding an Allen deviation of 7 pm in 0.03 s. For SR-POEM, we will improve the deviation to 0.1 pm in 1 s. [Preview Abstract] |
Monday, February 15, 2010 4:54PM - 5:06PM |
S10.00008: New Tests of Relativity Jay D. Tasson, Alan Kostelecky New ways of using gravitational experiments to test relativity have been revealed by recent studies. Experimental results based on lunar laser ranging, torsion pendula, and high- sensitivity gravimetry have already been obtained. Many more tests have been proposed, including qualitatively new searches based on tests of weak equivalence. In some cases, the proposed tests would constitute the first searches for certain types of relativity violation. This presentation will provide an outline of the modern theoretical framework for testing relativity, the gravitational Standard-Model Extension, and a summary of recent experimental results and proposals. [Preview Abstract] |
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