RUI: Parallel-Plate Torsion Pendulum for Investigations of Short-range Gravitational Physics

该项目的目标是在前所未有的水平上测试广义相对论的弱等效原理（WEP）和引力平方反比定律（ISL）。WEP将在毫米尺度上进行测试，而ISL将以前所未有的灵敏度在亚毫米距离上进行探测。两项试验都将使用一种新型的平行板扭摆设计。自1999年以来，实验限制得到了显著改善，因此ISL已被证明在距离低至约55微米的范围内有效。然而，WEP的专用测试尚未在毫米尺度以下进行。根据该合同的初始工作将探测毫米及以下尺度的WEP。这项测量将通过一种新颖的平行板扭摆设计来完成，这种设计将提供一个本质上无效的实验，并使用多种成分偶极子组合。随后，将进行更困难的引力ISL测试，将钟摆/吸引子质量分离减小到100微米。这种配置将探测ISL到大约20微米的距离。近年来，在短（亚毫米）距离尺度上对引力相互作用的研究受到了广泛关注，这在很大程度上是由于弦理论或m理论中出现的统一场景，这些场景需要三维以上的空间维度，其中一些可能是宏观的。对引力和WEP的短程测试也研究了可能提出的机制，这些机制试图解释宇宙的加速膨胀，通常归因于暗能量。最后，这样的测试提供了寻找由外来粒子或其他现象引起的假设的新相互作用的可能性。关于这些效应的许多设想都预测了在短距离上WEP或引力ISL的破坏。该项目将在洪堡州立大学的引力物理实验室进行，这是洪堡州立大学物理系本科生获得实际研究经验的唯一场所。该奖项为实验室提供持续的支持，本科生津贴，设备改进，以及支持包括学生演讲在内的成果传播。与华盛顿大学Eöt-Wash小组的合作将加快加工项目，并允许每年从洪堡州立大学的一名本科生在夏季期间作为本科生研究助理与小组一起获得宝贵的经验。此外，为数据采集和分析而开发的软件工具将转移到高年级课堂的教育机会中。

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.