Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session S11: Invited Session: Precision Experimental Measurements of Gravitation |
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Sponsoring Units: GGR GPMFC Chair: Stephan Schlamminger, National Institute of Standards and Technology Room: Key 7 |
Monday, April 13, 2015 1:30PM - 2:06PM |
S11.00001: Experimental tests of the Einstein Equivalence Principle Invited Speaker: Michael Hohensee The Einstein Equivalence Principle (EEP) is fundamental to General Relativity (GR) and the Standard Model (SM) of particle physics. Consequently, it has been long been subject to stringent experimental tests--first to verify the general validity of both models, and more recently to search for hints of new physics. This talk will review the current status of experimental constraints on modified gravity and EEP-violation in the context of the Standard Model Extension, a phenomenological framework that can consistently describe small EEP-violating deviations from GR and the SM. We will outline promising areas for future investigation, and describe some exciting new experiments using trapped ions which can test EEP for electrons with orders of magnitude more sensitivity than previous tests. Prepared by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
Monday, April 13, 2015 2:06PM - 2:42PM |
S11.00002: Why is it so difficult to measure big G? Invited Speaker: James Faller The determination of the Newtonian constant of gravitation, big G, continues to be one of Nature's greatest challenges to the skills and cunning of experimental physicists. The reasons: Big G is small, scientists are human, and error budgets are flawed. In spite of the fact that on the scale of the Universe, big G's effects are so big as to single handedly hold everything together, on the scale of a single research laboratory, big G's effects are so small that they go unnoticed. And, it is this ``smallness'' that makes the determination of this (seemingly unrelated to the rest of physics) fundamental constant so difficult. Furthermore, because they are human, scientists want to get the ``right'' (read previously obtained) answer; and this goal can affect their otherwise good judgment. Finally, error budgets are fundamentally flawed because they cannot make allowances for error sources that have not been thought of. During its nearly 300 year measurement history, the accuracy with which G is known has barely increased by three orders of magnitude; during the past 30 years the progress, measured by agreement rather than claimed accuracy of individual measurements, has been essentially zero. Nevertheless, this Mount Everest of precision measurement continues to provide an experimental challenge upon which metrologists can hone their laboratory skills for generations to come. Finally, this presentation will be understandable and interesting for ``students of all ages.'' In this year of GR100, Einstein will be mentioned more than once, and my hope is that some of you who would not normally ``risk'' attending a talk outside of your own specialty or discipline will consider coming to this one. [Preview Abstract] |
Monday, April 13, 2015 2:42PM - 3:18PM |
S11.00003: Testing Newton's Gravitational Inverse-Square Law Invited Speaker: Charles Hagedorn Newton's inverse-square law of gravitation is the oldest standing mathematical description of a fundamental interaction. Experimental tests of gravity's distance-dependence define a frontier between our understanding of gravity and many proposed forms of new physics. These experiments constrain the size of possible extra dimensions, bound attempted resolution of the cosmological-constant problem, search for self-interacting chameleons, make direct measurements at the dark-energy length-scale, and more. As gravity is $\sim10^{40}$ times weaker than electromagnetism, gravity remains hidden by experimental backgrounds at distances smaller than the diameter of a fine human hair. This talk will survey the past, present, and near-future of the experimental field, with substantial emphasis on precision sub-millimeter laboratory experiments. [Preview Abstract] |
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