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

引力是自然界中四种基本相互作用之一。但与其他三种相互作用（电磁力、弱力和强力）不同，它的理论描述基于牛顿的万有引力，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，理论物理学中的一些现代提议提出，平方反比定律（ISL）可能在实验上可达到的亚毫米间隔上被打破，从而为统一引力与量子理论提供了诱人的前景。拟议的研究将利用最灵敏的台式仪器之一，扭转天平，直接探测100微米以下的ISL。从这项研究中获得的具体结果，与本科生和华盛顿大学的Eot-Wash小组合作，将增加基础研究的基础知识，并对从天体物理学到基本粒子和核物理学的广泛物理学领域产生深远的影响。 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配置中的短程引力。该策略使得有可能进行低于70微米的高精度实验，其中界面表面的粗糙度和平面度是唯一的限制性物理障碍。因此，该方法将大大提高汤川空间在10微米范围内的电流极限四倍。拟议研究的另一个新奇是探测汤川空间中一厘米以上的重力，这是一个以前未探索过的范围。从技术的角度来看，在测试物体之间插入静电屏，在这种尺度上探测重力将大大减少近场效应，如电贴片效应和卡西米尔力。最后，拟议的研究将为学生提供校内动手研究的机会，加强PI实验室精密力测量领域的现有研究计划。过去在本科研究中经常教授的实验室技术的例子包括：低噪声锁定测量，电子电路的设计和构造，干涉测量技术，例如光纤和迈克尔逊干涉仪，以执行精确位移测量，各种扫描探针显微镜技术，例如STM、AFM和KPM，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.