Probing Fundamental Physics with Gravitational Experiments

在《现代物理学》中，有两个被广泛接受的理论描述了整个自然界。一种是描述所有材料属性的“标准模型”。标准模型包含了所有的量子粒子。另一个理论是“广义相对论”，即爱因斯坦描述万有引力的理论。尽管有一些相似之处，但这两个理论非常不同，并且没有经过验证的理论或实验证据将两者联系起来，尽管大多数物理学家认为它们之间一定存在联系。这个小组专门测量非常小的力来进行超精确的重力测试。在团队进行的所有测试中，他们试图找到与普通重力的微小偏差。如果这些偏差被发现，这将意味着广义相对论还有更多的东西，或者这是第三个基本理论的暗示，或者这是如何统一标准模型和广义相对论的暗示。具体来说，该小组专门开发和使用扭转平衡仪器来测试等效原理（EP）：几乎可以肯定，广义相对论和标准模型之间的任何联系都违反了等效原理。该集团使用的扭力天平可提供迄今为止最精确的EP测试。通过技术创新：引入熔融石英纤维和应用两种新方法来跟踪环境重力梯度，测量的灵敏度将增加一倍或更多。该实验的普遍性和与宇宙学的相关性将通过探测带氢的测试质量来增强。2)寻找自旋耦合力和洛伦兹违反的线索：本征自旋是标准模型相互作用的基础，但显然不是广义相对论的基础。利用该小组的自旋极化实验结果，将对新兴的超轻暗物质候选者施加限制。3)在短距离内测试牛顿反平方定理（ISL）：该小组的实验保持了观测到重力的最短距离记录，将重力强度的ISL偏差限制在小于42微米的距离内。该小组将对现有的120倍对称ISL设备进行升级，并继续推进更小的距离。4)推进低频小力技术前沿：创新和具有挑战性的技术开发是集团成功的基础。展望该领域的未来，该小组将继续完善超低噪音低温扭转平衡和高灵敏度，但用户友好的光学角度传感仪器。低频重力强度测量所需的创造性技术进步已经并将对包括引力波探测在内的相关领域产生影响。在NSF的投资下，该集团建立了一个强大的世界领先的实验室，拥有独特的专业知识和基础设施，能够以高效和严谨的方式解决这些实验挑战。

In Modern Physics there are two very well accepted theories that describe all of nature. One is the 'Standard Model' which describes all material properties. The Standard Model contains all the quantum particles. The other theory is 'General Relativity', Einstein's theory that describes gravitation. Despite some similarities, these two theories are very different and there is no verified theory or experimental evidence connecting the two, even though most physicists think that there must be a connection. This group specializes on measuring very small forces to conduct ultra-precise tests of gravity. In all the tests carried out by the team, they try to find ever so small deviations from ordinary gravity. If such deviations are found, it would mean that there is more to general relativity, or that this is hint of a third fundamental theory, or that this is a hint of how to unify the Standard Model and General Relativity.Specifically the group is specialized in developing and using torsion balance instruments to1) Test the equivalence principle (EP): It is almost certain that any connection between General Relativity and the Standard Model violates the EP. The torsion balances utilized by the group provide the most precise EP tests to date. The measurement's sensitivity will be doubled, or more, through technical innovation: introducing fused silica fibers and by applying two new methods to track ambient gravity gradients. The experiment's generality and relevance to cosmology will be enhanced by probing the EP with hydrogen-bearing test masses.2) Search for spin-coupled forces and hints of Lorentz violation: Intrinsic spin is fundamental to the standard model interactions but apparently not to general relativity. Leveraging the group's spin-polarized experimental results, constraints will be placed on an emerging class of ultra-light dark matter candidates.3) Test Newton's Inverse-Square (ISL) at short distances: The group's experiments hold the record for the shortest distance at which gravity has been observed, constraining gravity-strength ISL deviation to act over distances less than 42 microns. The group will commission existing upgrades to their 120-fold-symmetric ISL apparatus and press onward to yet smaller distances.4) Advance the frontier of low-frequency small-force technology: Innovative and challenging technology development has underpinned the group's success. Looking to the future of the field, the group will continue to refine both an ultra-low noise cryogenic torsion balance and highly-sensitive, but user-friendly, optical angle-sensing instruments. The creative technical advances required for gravitational strength force measurement at low frequency have had and will have impact on related fields, including gravitational-wave detection. With NSF investment, the group has built up a strong world-leading laboratory with unique expertise and infrastructure in position to address these experimental challenges with efficiency and rigor.