Probing Fundamental Physics with Gravitational Experiments

在现代物理学中，有两种广为接受的理论描述了整个自然。一种是描述所有材料属性的“标准模型”。标准模型包含所有量子粒子。另一个理论是“广义相对论”，爱因斯坦描述引力的理论。 尽管有一些相似之处，但这两种理论还是非常不同的，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肯定存在联系。 该小组专门测量非常小的力以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。如果发现这样的偏差，那就意味着广义相对论还有更多的内容，或者这是第三种基本理论的暗示，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力天平仪器来1）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EP。该小组使用的扭转天平提供了迄今为止最精确的 EP 测试。通过技术创新，测量的灵敏度将提高一倍或更多：引入熔融石英纤维并应用两种新方法来跟踪环境重力梯度。通过用含氢测试质量探测 EP，该实验的普遍性和与宇宙学的相关性将得到增强。2) 寻找自旋耦合力和洛伦兹破坏的暗示：内禀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，将对一类新兴的超轻暗物质候选者进行限制。3）短距离测试牛顿反方（ISL）：该小组的实验保持着观测到重力的最短距离的记录，限制了重力强度ISL偏差在小于42微米的距离内起作用。该集团将对其 120 倍对称 ISL 设备进行现有升级，并向更小的距离迈进。4) 推进低频小力技术的前沿：创新和具有挑战性的技术开发是该集团成功的基础。展望该领域的未来，该集团将继续改进超低噪声低温扭转天平和高灵敏度但用户友好的光学角度传感仪器。低频引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。通过 NSF 的投资，该小组建立了一个强大的世界领先实验室，拥有独特的专业知识和基础设施，能够高效、严谨地应对这些实验挑战。

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.