A Test of Newtonian Gravity at the 25 Micron Length Scale PDF Download
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Author: Sylvia J. Smullin
Publisher:
ISBN:
Category :
Languages : en
Pages : 214
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Author: Sylvia J. Smullin
Publisher:
ISBN:
Category :
Languages : en
Pages : 214
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Author: Andrew A. Geraci
Publisher:
ISBN: 9780549060581
Category :
Languages : en
Pages : 150
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Book Description
Several recent theories suggest that new physics related to gravity may appear at short length scales. For example, light moduli from string theory or exotic particles in "large" extra dimensions could mediate macroscopic forces of (super) gravitational strength at length scales below a millimeter. Such new forces can be parameterized as a Yukawa-type correction to the Newtonian potential of strength relative to gravity alpha and range lambda. With this motivation, we have built a cryogenic apparatus utilizing micro-cantilevers capable of measuring atto-Newton forces, which now includes a magnetic force calibration. The cantilever is loaded with a rectangular gold prism fabricated by focused-ion-beam milling that serves as a test mass for the experiment. The driving (source) mass is actuated horizontally beneath the cantilever at a vertical separation of order 25 microns. The force between the masses is deduced from the displacement of the cantilever as measured by a fiber-coupled laser interferometer. We perform the measurement at the cantilever resonant frequency, typically of order 300 Hz, while the mechanical driving motion occurs at a sub-harmonic, typically one-third. This is achieved by implementing a density modulation in the drive mass, consisting of alternating gold and silicon sections. For the new magnetic calibration, Co/Pt multi-layer films are deposited on the test mass. The permanent magnetic moment couples to an induced magnetic field gradient as current flows across the meandering gold sections in the drive mass device. The current is turned off for the Yukawa-force search. A mu-metal shield encloses the cryostat to prevent the Earth's field from magnetizing the drive mass. The amplitude and phase of a magnetic or Yukawa signal will change in a predictable way as we vary the equilibrium position of the drive mass oscillation. We utilize this scanning technique as an additional handle to distinguish a signal from background forces. Our most recent experimental constraints on Yukawa-type deviations from Newtonian gravity are more than three times as stringent as our previously published results, and represent the best bound in the range of 5--15 microns, with a 95-percent confidence exclusion of forces with alpha > 14,000 at lambda of 10 microns.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 780
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Author: Ted S. Cook
Publisher:
ISBN:
Category : Gravity
Languages : en
Pages : 147
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Proposed theories that unify gravity and quantum mechanics often require Newton's gravitational inverse-square law to fail below some length scale. Additionally, some theorists have proposed the discovery of Dark Energy may imply altered gravitational dynamics at short length scales. These facts motivated our previous and continued efforts to test gravity at the smallest achievable distances. This dissertation describes an improved test of gravity using a torsion pendulum and attractor designed with 120-fold azimuthal symmetry. We tested the inverse-square law at separations down to 60 microns and have excluded gravity-strength Yukawa interactions with length scale > 42 microns at the 95% confidence level. However, our data preferred the inclusion of a Yukawa potential at longer length scales, in a region of parameter space previously excluded by experiment, indicating some yet unresolved systematic issues. This dissertation provides a complete description of the experiment and gives guidance for improved future measurement.
Author:
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ISBN:
Category : Nuclear energy
Languages : en
Pages : 1412
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Author:
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ISBN:
Category :
Languages : en
Pages :
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We predicted gravity values on a tower by upward continuing an extensive set of surface data in order to test the 1/r2 dependence of Newton's Law of Universal Gravitation. We measured gravity at 12 heights up to 454 m on a tower at the Nevada Test Site, and at 91 locations on the surface of the earth within 2.5 kilometers of the tower. These data have been combined with 60,000 surface gravity measurements within 300 kilometers of the tower and have been used to predict the gravitational field on the tower via a solution of Laplace's equation. A discrepancy between the observed gravity values and the prediction could suggest a breakdown of Newtonian Gravity, but we observe none. Our preliminary results are consistent with the Newtonian hypothesis to within 93 +- 95 .mu.gals at the top of the tower, a result which conflicts with the previously reported 500 .mu.gal non-Newtonian signal seen at 562 meters above the earth. 24 refs., 2 figs.
Author: Emmanuel N. Saridakis
Publisher: Springer Nature
ISBN: 3030837157
Category : Science
Languages : en
Pages : 631
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Book Description
With a focus on modified gravity this book presents a review of the recent developments in the fields of gravity and cosmology, presenting the state of the art, high-lighting the open problems, and outlining the directions of future research. General Relativity and the ΛCDM framework are currently the standard lore and constitute the concordance paradigm of cosmology. Nevertheless, long-standing open theoretical issues, as well as possible new observational ones arising from the explosive development of cosmology in the last two decades, offer the motivation and lead a large amount of research to be devoted in constructing various extensions and modifications. In this review all extended theories and scenarios are first examined under the light of theoretical consistency, and are then applied in various geometrical backgrounds, such as the cosmological and the spherical symmetric ones. Their predictions at both the background and perturbation levels, and concerning cosmology at early, intermediate and late times, are then confronted with the huge amount of observational data that astrophysics and cosmology has been able to offer in the last two decades. Theories, scenarios and models that successfully and efficiently pass the above steps are classified as viable and are candidates for the description of Nature, allowing readers to get a clear overview of the state of the art and where the field of modified gravity is likely to go. This work was performed in the framework of the COST European Action “Cosmology and Astrophysics Network for Theoretical Advances and Training Actions” - CANTATA.
Author:
Publisher:
ISBN:
Category : Engineering
Languages : en
Pages : 1052
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Author: Bretislav Friedrich
Publisher: Springer Nature
ISBN: 3030639630
Category : Science
Languages : en
Pages : 639
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Book Description
This Open Access book gives a comprehensive account of both the history and current achievements of molecular beam research. In 1919, Otto Stern launched the revolutionary molecular beam technique. This technique made it possible to send atoms and molecules with well-defined momentum through vacuum and to measure with high accuracy the deflections they underwent when acted upon by transversal forces. These measurements revealed unforeseen quantum properties of nuclei, atoms, and molecules that became the basis for our current understanding of quantum matter. This volume shows that many key areas of modern physics and chemistry owe their beginnings to the seminal molecular beam work of Otto Stern and his school. Written by internationally recognized experts, the contributions in this volume will help experienced researchers and incoming graduate students alike to keep abreast of current developments in molecular beam research as well as to appreciate the history and evolution of this powerful method and the knowledge it reveals.
Author:
Publisher:
ISBN:
Category : Particles
Languages : en
Pages : 208
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