| NSF Org: |
PHY Division Of Physics |
| Recipient: |
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| Initial Amendment Date: | April 27, 2018 |
| Latest Amendment Date: | March 3, 2020 |
| Award Number: | 1802952 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Pedro Marronetti
pmarrone@nsf.gov (703)292-7372 PHY Division Of Physics MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | May 1, 2018 |
| End Date: | April 30, 2021 (Estimated) |
| Total Intended Award Amount: | $400,000.00 |
| Total Awarded Amount to Date: | $400,000.00 |
| Funds Obligated to Date: |
FY 2019 = $133,333.00 FY 2020 = $133,334.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
450 JANE STANFORD WAY STANFORD CA US 94305-2004 (650)723-2300 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
382 Via Pueblo Mall Stanford CA US 94305-4060 |
| 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): |
AMO Experiment/Atomic, Molecul, Gravity Exp. & Data Analysis |
| Primary Program Source: |
01001920DB NSF RESEARCH & RELATED ACTIVIT 01002021DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
This award is supported by the Gravitational Physics and the Atomic, Molecular and Optical Experimental Physics programs. Understanding the nature of gravity at microscopic distances is one of the most important open problems in fundamental physics. Although General Relativity provides an extremely well-tested framework for describing gravitational effects at large distances, it cannot be consistently combined with the Standard Model of particle physics to provide a description of gravity at small scales. The development of a quantum theory of gravity that can be incorporated into the Standard Model is a central goal of fundamental physics, with broad implications for our understanding of particle physics and the mysterious nature of the "dark energy" that appears to permeate the universe. Many theories attempting to provide a consistent microscopic framework for gravity (e.g., those involving extra dimensions) predict that gravity could deviate from the familiar inverse square law at distances shorter than a mm. Such deviations are extremely difficult to measure experimentally due to the small strength of gravitational interactions at microscopic distances. The studies described here attempt to gain insights into the realm of microscopic gravitational forces with a novel experimental setup. Additionally, the research will enhance the training of students in STEM areas which are vital for the future of the nation.
Previous measurements at these distance scales have employed techniques derived from human-size devices in which mechanical springs are used as force sensors. This group has developed a drastically new technique, using the light field of a laser to confine and measure the motion of micron (or, eventually, submicron)-size quartz microsphere. Previous studies undertaken by this group include the most sensitive search to date for fractional charges over 4 orders of magnitude smaller than the charge of an electron. This is a by-product of having to discharge the microspheres and check that they are really neutral. The group has completed the construction of a new trap in which the entire microsphere position readout is carried out interferometrically. This is a first in this area of research and will be applicable to other areas, e.g. biology or polymer science. The studies supported by this grant include exploring the possibility of spinning the microspheres, something that could reduce the background of the gravity measurements and may also lead to the development of nanogyroscopes.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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.
Of the four fundamental interactions that affect all known phenomena in nature, gravity is the one we all experience (for instance, it is the reason we can walk on planet earth and do not float away in space!). Yet, the gravitational interaction is also the one we have the most trouble understanding at a profound level. Maybe most notable, gravity is the weakest of the fundamental interactions --by a very large stretch-- and, according to Einstein's General Relativity, it has the distinction of being due to properties of the very spacetime environment in which everything else --including all other interactions-- operate. Furthermore, we have not been able to properly connect gravity with quantum mechanics, the framework describing objects at the smallest scale, such as atoms.
This grant continued to support a small program towards a better empirical understanding of gravity at short distance, searching for deviations from the inverse square law introduced by Isaac Newton 350 years ago. Such deviations, if discovered, could indicate the existance of new interactions, or suggest that space has more than the familiar three dimensions. A new technique has been developed towards better quality measurements in this area. The first paper describing results in this area was published a few months ago and is currently undergoing peer review.
As it is often the case in science, the development of the tools for this exceedingly challenging measurements have applications to several other areas of science and technology. In the course of this work we have developed a new technique to perform 3-dimensional force microscopy, i.e. to measure the force vector, with a ~10 attoNewton sensitivity, in relatively large volumes of space. We have also been able to improve the sensitivity for hypothetical particles with charges that are much smaller than that of the electron. Finally, we have developed a new way to control the rotation of dielectric microspheres held in an optical trap, which in turn resulted to new technique to measure vacuum and the average molecular composition of a gas at low pressure.
Last Modified: 07/20/2021
Modified by: Giorgio Gratta
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