Probing Fundamental Physics with Gravitational Experiments

点击翻译按钮获取中文摘要

In modern physics Nature is described by two theories. One is the “Standard Model,” which describes all material properties with quantum particles; the other is “General Relativity”, Einstein’s theory that describes gravitation. Most physicists think that there must be a connection between these two theories, but to date there is no experimental signature for such a connection. Furthermore, the discoveries of dark matter and dark energy suggest that gravitational phenomena exist that lie outside of General Relativity. The group at the University of Washington specializes in measuring ultra-feeble forces to search for unprecedentedly small deviations from gravity as described by General Relativity. While observing any deviations from General Relativity would be a revolutionary scientific discovery, it may also have consequences for future technical applications of GPS or next-generation precision clocks. Technology and technical expertise developed by this group has applications ranging from industrial metrology to earthquake prediction. Modern ideas for unifying gravity and particle physics, as well as the observation of dark energy and dark matter, suggest that some aspects of gravity remain undiscovered. The table-top experiments of the University of Washington gravity laboratory (Eöt-Wash Group) provide a unique opportunity to search for new physics at the intersection of General Relativity, cosmology, and particle physics. The group is a leader in the field of ultra-weak force detection through technical expertise, innovation, and by responding to the most relevant timely and timeless physics questions. Specifically, the group will:1) Test the equivalence principle (EP): It is almost certain that any connection between General Relativity and the Standard Model violates the EP. The group’s torsion balances provide the most precise EP-tests at distances below 100 km. With highly-increased sensitivity through fused silica torsion fibers, a new EP measurement will be carried out. The experiment’s generality and relevance to cosmology will be enhanced by probing the EP with hydrogen test masses. 2) Test Newton’s Inverse-Square Law at short distances: The Eöt-Wash group has measured and tested gravity at distances of 41 μm. The group will use its expertise to design and build a new instrument aimed at measuring and testing gravity down to distances of 25 μm. 3) Advance the frontier of low-frequency ultra-small-force technology: Innovative and challenging technology development has enabled the group’s success. With a vision towards the future of gravitational research (including LIGO), the group will continue pursuing development of cryogenic instruments and interferometric torsion balance readout.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.