Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session L11: Experimental Gravitation |
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Sponsoring Units: GGR Chair: Duncan Brown, California Institute of Technology Room: Hyatt Regency Dallas Cumberland E |
Sunday, April 23, 2006 3:15PM - 3:27PM |
L11.00001: Post-Newtonian Gravity with Lorentz Violation Quentin G. Bailey, Alan Kostelecky Lorentz-symmetry violation is a popular candidate signal for Planck-scale physics. The general description of observable Lorentz-symmetry violation at low energies is given by the Standard-Model Extension (SME). This talk discusses the pure gravitational sector of the SME in the limit of Riemann geometry and presents some key results for the post-newtonian limit. We outline several promising possibilities for experimental searches, including some with the potential to access unmeasured coefficients for Lorentz violation and others that could improve existing sensitivities. [Preview Abstract] |
Sunday, April 23, 2006 3:27PM - 3:39PM |
L11.00002: Building and Testing A New Apparatus for Measuring Mass-dependent Forces at Small Length Scales David Weld, Jing Xia, Blas Cabrera, Aharon Kapitulnik We will discuss the construction and initial testing of a new type of cantilever-based probe for measuring mass-dependent forces at length scales of order $10^{-5}$ meters. The apparatus is based on a cryogenic helium gas bearing with a hemispherical quartz rotor. The bearing housing contains a force-sensing microcantilever with a metallic test mass mounted on the tip. An alternating pattern of high- and low-density materials is embedded in the flat surface of the rotor so that when the rotor spins, the mass on the cantilever is subjected to an AC gravitational force. This design combines some of the geometrical advantages of torsion-balance experiments with the small face-to-face separation and good force sensitivity of our previous cantilever-based experiments [1,2]. [1] S. J. Smullin et al., Phys. Rev. D 72, 122001 (2005) [2] J. Chiaverini et al., Phys. Rev. Lett. 90 , 151101 (2003) [Preview Abstract] |
Sunday, April 23, 2006 3:39PM - 3:51PM |
L11.00003: Design and performance of a sub-nanoradian resolution Autocollimating optical lever Ramanath Cowsik, R. Srinivasan, S. Kasturirengan, A. Senthil Kumar, Kasey Wagoner Precision goniometry using optics has the advantage that it does not impose much stress on the object of investigation and, as such, is adopted extensively in gravitational wave detection, in torsion balances investigating fundamental forces and in specialized studies of biological samples. It has potential applications in condensed matter physics. We have developed an autocollimating optical lever which has a very high resolution and dynamic range. An array of 110 slits, of 84 micron width and a pitch of 182 microns, is located in the focal plane of a field lens, of focal length 1000 mm, and is illuminated by a CCFL-tube. This array is imaged back on to the focal plane after retro-reflection from a mirror placed just beyond the lens. The image was recorded on a linear CCD array at the rate of 1000 images per second and was processed through a special algorithm to obtain the centroid. The instrument has a centroid stability of $\sim $ 3.10$^{-10}$ rad.Hz$^{-1/2}$ and a dynamic range of $\sim $ 10$^{7}$. [Preview Abstract] |
Sunday, April 23, 2006 3:51PM - 4:03PM |
L11.00004: Adaptive Mode matching in stable recycling cavities in Advanced LIGO G. Mueller, M.A. Arain, V. Quetschke, D.H. Reitze, D.B. Tanner The Laser Interferometer Gravitational-Wave Observatory has reached its design sensitivity and is currently in its fifth science run (S5). One of the main obstacles in reaching the design sensitivity was the imbalance of the RF-sidebands inside the unstable and thermally loaded recycling cavity, requiring the implementation of external thermal compensation and ultra-stable RF oscillators to overcome this problem. These effects will be amplified in Advanced LIGO, which will operate at 15 times greater laser power. Thermal deformations excite higher order spatial modes which are resonantly enhanced for the RF-sidebands and the gravitational-wave-induced signal sidebands. This may lead to signal loss and perhaps to instabilities which could prevent high power operation. We propose to develop stable recycling cavities and compensate the remaining thermally driven losses with an adaptive mode-matching system. We will discuss the physics behind these effects, describe how the system is analyzed, and discuss the current status of the analysis. . [Preview Abstract] |
Sunday, April 23, 2006 4:03PM - 4:15PM |
L11.00005: The scaling of LIGO's coating thermal noise with beam shape Geoffrey Lovelace An option for Advanced LIGO is to alter the light beam's cross sectional shape so as to reduce thermal noise in the mirrors' substrates and coatings. The influence of beam shape on substrate noise is fairly well understood\footnote{ E. D'Ambrosio, R. O'Shaughnessy, S. Strigin, K. Thorne and S. Vyatchanin, Phys. Rev. D submitted, gr-qc/0409075.\par }, and J. Agresti has compared Gaussian and flat-top shapes for coating noise\footnote{ Juri Agresti, preliminary results. LIGO-G050041-00-Z, available at http://www.ligo.caltech.edu/.}. Unpublished analyses by R. O'Shaughnessy and S. Vyatchanin suggest that, if one approximates the mirrors as semi-infinite, the coating thermal noise below any point on the mirror surface is proportional to the square of the beam intensity \textit{at that point}, i.e., the noise obeys a \textit{local} scaling law. Using the fluctuation-dissipation theorem and elastostatics, I show that the correct scaling also includes \textit{nonlocal} terms. I comment on the implications of this result for Advanced LIGO. [Preview Abstract] |
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