RUI: Search for Non-Newtonian Gravity Using a High-Sensitivity Torsion Balance at Seattle University

重力是自然界四大基本相互作用之一。但与其他三种相互作用(电磁、弱和强相互作用)不同的是，它基于牛顿万有引力的理论描述，后来被爱因斯坦的广义相对论扩展，与标准模型不兼容，标准模型是一个统一了所有其他三种相互作用的量子力学框架。面对这种二分法，理论物理中的一些现代提议表明，平方反比定律(ISL)可能会在实验上可达亚毫米的距离下崩溃，从而为将引力与量子理论统一提供了诱人的前景。这项拟议的研究将利用最灵敏的桌面仪器之一--扭转天平--直接探测100微米以下的ISL。因此，与本科生和华盛顿大学EOT-Wash小组合作，从这项研究中获得的具体结果将增加基础研究的基本知识，并对从天体物理到基本粒子和核物理的广泛物理领域产生深远影响。这项拟议的研究旨在通过直接量化非引力相互作用的贡献来测试平行平面构型中的短程重力。这一策略使在70微米以下进行高精度实验成为可能，而对接表面的粗糙度和平面度是唯一的限制物理障碍。因此，该方法将极大地改善目前对汤川空间10微米范围的限制，提高四倍。这项拟议中的研究的另一个新奇之处是探测汤川空间一厘米以上的重力，这是一个以前从未探索过的范围。从技术角度来看，由于在测试体之间插入静电屏，在这种尺度上探测重力将显著减少近场效应，如电斑块效应和卡西米尔力。最后，拟议的研究将为学生提供在校园内动手进行研究的机会，加强PI实验室在精密测力领域的现有研究计划。过去在本科生研究中常规教授的实验室技术的例子包括：低噪声锁定测量，电子电路的设计和建造，干涉技术，如光纤和迈克尔逊干涉仪来执行精确的位移测量，各种扫描探针显微镜技术，如STM，AFM和KPM，可在华盛顿大学NSF资助的华盛顿纳米制造设施(WNF)获得。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Gravity represents one of the four fundamental interactions in nature. But unlike the other three interactions (electromagnetism, weak, and strong forces), its theoretical descriptions based on Newton's universal gravitation, later expanded by Einstein's General Relativity, are incompatible with the Standard Model, a quantum-mechanical framework that unifies all of the other three interactions. Faced with this dichotomy, some modern proposals in theoretical physics have suggested a possible breakdown of the inverse-square law (ISL) at experimentally-accessible sub-millimeter separations, thereby providing a tantalizing prospect for unifying gravity with quantum theory. The proposed research will utilize one of the most sensitive table-top instruments, a torsional balance, to directly probe the ISL below 100 micrometers. Specific results obtained from this research, in collaboration with undergraduate students and the Eot-Wash group of the University of Washington, will thus increase basic knowledge in fundamental research and have profound impacts across broad areas of physics ranging from astrophysics to elementary particle and nuclear physics. The proposed research aims to test short-range gravity in the parallel-plane configuration by directly quantifying the contributions from non-gravitational interactions. The strategy makes it possible to conduct a high-precision experiment below 70 micrometers for which the roughness and planarity of the interfacing surfaces are the only limiting physical barriers. The approach will thus substantially improve the current limits on the Yukawa space at the 10 micrometer range by a factor of four. Another novelty of the proposed research is to probe gravity above one cm in the Yukawa space, a previously unexplored range. From a technical perspective, with an electrostatic screen inserted between the test bodies, probing gravity at this scale would significantly reduce the near-field effects, such as the electric patch effect and the Casimir force. Finally, the proposed research will provide on-campus, hands-on research opportunities for students, enhancing an existing research program in the area of precision force measurements in the PI's lab. Examples of the laboratory techniques routinely taught in undergraduate research in the past include: low-noise lock-in measurements, design and construction of electronic circuits, interferometric techniques, such as fiber-optic and Michelson's interferometer to perform precision displacement measurements, various scanning probe microscopy techniques, such as STM, AFM, and KPM, that are accessible at the NSF-funded Washington Nanofabrication Facility (WNF) at the University of Washington.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.