| NSF Org: |
PHY Division Of Physics |
| Recipient: |
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| Initial Amendment Date: | July 28, 2011 |
| Latest Amendment Date: | July 28, 2011 |
| Award Number: | 1065697 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Pedro Marronetti
pmarrone@nsf.gov (703)292-7372 PHY Division Of Physics MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | August 1, 2011 |
| End Date: | July 31, 2014 (Estimated) |
| Total Intended Award Amount: | $117,157.00 |
| Total Awarded Amount to Date: | $117,157.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1 HARPST ST ARCATA CA US 95521-8222 (707)826-4189 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1 harpst street arcata CA US 95521-8299 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Gravity Exp. & Data Analysis |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
The goal of this project is to test the Weak Equivalence Principle (WEP) of General Relativity and the gravitational inverse-square law (ISL) at unprecedented levels. The WEP will be tested at the millimeter scale and the ISL will be probed over sub-millimeter distances with unprecedented sensitivity. Both tests will use a novel parallel-plate torsion pendulum design. Since 1999, experimental limits have improved dramatically so that the ISL has proven valid over distances down to approximately 55 micrometers. A dedicated test of the WEP, however, has not been performed below the millimeter scale. The initial work under this award will probe the WEP at the millimeter scale and below. This measurement will be accomplished with a novel parallel-plate torsion pendulum design that will provide an essentially null experiment and use multiple composition dipole combinations. Subsequently, a more difficult test of the gravitational ISL will be pursued by decreasing the pendulum/attractor mass separation to 100 micrometers. This configuration will probe the ISL down to distances of approximately 20 micrometers.
In recent years the study of the gravitational interaction at short (sub-millimeter) distance scales has gained much attention due in a large part to unification scenarios arising in string or M-theory that require more than three spatial dimensions, some of which could be macroscopic. Short-range tests of gravity and the WEP also investigate possible proposed mechanisms that endeavor to explain the accelerated expansion of the universe, generally attributed to Dark Energy. Finally, such tests present the possibility to search for hypothetical new interactions due to exotic particles or other phenomena. Many scenarios concerning these effects predict a violation of the WEP or gravitational ISL at short distances. The project will be performed in the Gravitational Physics Laboratory at Humboldt State University, the only arena in which undergraduate physics students at Humboldt State University may obtain hands-on research experience. This award provides continued support for the laboratory, undergraduate stipends, equipment improvements, and support for dissemination of results including student presentations. Collaboration with the University of Washington Eöt-Wash group will expedite machining projects as well as allow one undergraduate per year from Humboldt State to gain valuable experience working with the group as an undergraduate research assistant during the summer months. In addition, software tools developed for data acquisition and analysis will be transferrable to educational opportunities in the upper division classroom.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The research performed at Humboldt State University (HSU) funded by this award involved the development of novel experiments to test the fundamental nature of gravity at short distance scales. Specifically, the award supported the development and commissioning phase of a torsion pendulum apparatus that is used to test Newton's inverse-square law of gravity and the Weak Equivalence Principle of Einstein's General Relativity at sub-millimeter distances. The majority of the research performed during this period was carried out by undergraduates under the supervision of the PI. The Gravitational Research Lab is a vital resource as it is the only hands-on research laboratory available to train undergraduates in the Department of Physics and Astronomy at HSU.
Recently, the importance of testing gravity at short distance scales has become evident due to the fact that certain efforts to combine the General Relativity and the Standard Model, including some versions of string theory, predict that gravity might behave fundamentally different at these distances. Furthermore, certain models proposed to explain Dark Energy also suggest possible anomalous gravitational behavior in this regime. Finally, some theoretical scenarios predict hypothetical new particles and forces that may be revealed by the experiments developed under this award. There is broad interest across the physics and astronomy communities in understanding the exact behavior of gravity at sub-millimeter distances.
During the time period covered by this grant, the apparatus achieved its required sensitivity and the bulk of the experimental hardware and software has now been implemented. The majority of the design and implementation of the experiment was performed by undergraduate research assistants (including paid positions during the summer months and research credits during the academic year). Specific examples of student projects include: design and construction of a custom optical autocollimator system with the ability to measure the torsion pendulum twist to within one one-billionth of a radian, implementation of temperature and other sensors for measuring the impact of environmental effects on the data, programming data acquisition and analysis software on various platforms, design and construction of custom mechanical components and readout circuitry, collection and analysis of preliminary and diagnostic data, as well as presentation and publication of results at national and international conferences. The experiment currently is functioning as expected and will test gravity at unprecedented levels in the near future.
This award also established a collaboration between the HSU gravity lab and the Eöt-Wash group at the University of Washington, led by Professor Eric Adelberger. In particular, two students from HSU were funded to work with the group in Seattle for 10 weeks each. Since HSU is a small institution with limited resources, this award allowed these students to obtain experience in a world-leading research laboratory. Examples of collaborative student projects include the design and modeling of a precision electromagnet used in an Eöt-Wash experiment that searches for axions (a potential Dark Matter candidate particle), and characterization of vacuum adhesive properties for use in the group's own short-range gravity experiment. Both students returned to HSU to share their knowledge and experiences with other undergraduates through seminars and informal meetings.
A large portion of this project is dedicated to the training and education of undergraduates in research methods. A total of six undergraduates were directly supported by this award during this time period. Other undergraduates were indirectly supported through the opportunity to volunteer in the laboratory. Support included summer stipends, travel support to present research results at regional...
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