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Search for hypothetical corrections of Newtonian gravity at l~100nmRicardo S. Decca Department of Physics, IUPUI |
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CollaboratorsFunding Daniel L?pez Argonne National Labs Ephraim Fischbasch Purdue University Dennis E. Krausse Wabash College and Purdue University Valdimir M. Mostepanenko Noncommercial Partnership “Scientific Instruments”, Russia Galina L. Klimchitskaya North-West Technical University, Russia Ho Bun Chan University of Florida Jing Ding IUPUI Hua Xing IUPUI NSF, DOE, LANL |
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Jonathan L. Feng, Science 301, 795 (’03)What is the background? The strength of gravity for various numbers of large extra dimensions n, compared to the strength of electromagnetism (dotted) Without extra dimensions, gravity is weak relative to the electromagnetic force for all separation distances. With extra dimensions, the gravitational force rises steeply for small separations and may become comparable to electromagnetism at short distances. |
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Attractive forceDominant electronic force at small (~ 1 nm) separations Non-retarded: van der Waals Retarded: Casimir No mode restriction on the outside 2a |
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Yukawa-like potential? f1 f2 1 2 Arises from very different pictures: Compact extra-dimensions Exchange of single light (but massive, m =1/l) boson Moduli; Graviphotons; Dilatons; Hyperphotons; Axions PRL 98, 021101 (2007) |
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Yukawa-like potentialGet rid of the background altogether Arises from very different pictures: Compact extra-dimensions Exchange of light (but massive, m =1/l) boson -Moduli -Graviphotons -Dilatons -Hyperphotons -Axions How do we establish limits? Measure background and subtract it |
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Experimental setup |
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Dynamic measurements |
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Separation measurementzg = (2389.6 ± 0.1) nm, interferometer zi = ~(10000.0 ± 0.2) absolute interferometer zo = (6960.1 ± 0.5) nm, electrostatic calibration b = (210 ± 3) mm, optical microscope Q = ~(1.000 ± 0.001) mrad zmeas is determined using a known interaction zi, Q are measured for each position |
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Comparison with theoryAFM image of the Au plane vi: Fraction of the sample at separation zi |
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Comparison with theory |
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“Casimir-less” experimentsAu Au Ge Si MTO |
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“Casimir-less” experimentsSignal optimization: Work at wo!!! Heterodyne Oscillate plate at f1, sphere at f2 such that f1 + f2 = fo |
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1 sec10 sec 100 sec 1000 sec z = 500 nm |
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“Casimir-less” experimentsNet force! F Signal optimization: Work at wo!!! Oscillate plate at f1, sphere at f2 such that f1 + f2 = fo 95% confidence level |
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“Casimir-less” experiments |
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F |
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BackgroundAl2O3 Au Au Au Ge Si MTO Motion not parallel to the axis (too small) Step (0.1 nm needed) Difference in electrostatic force (0.1 mV needed) Difference in Au coating (unlikely) Au coating not thick enough (unlikely) |
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What next |
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Two orders of magnitude improvement |
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Conclusions Most sensitive measurements of the Casimir Force andCasimir Pressure Unprecedented agreement with theory First realization of a “Casimir-less” experiment Improvement of about three orders of magnitude in Yukawa-like hypothetical forces New experiment under way. Results expected by the end of the year. |
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