Understanding Gravity at the Smallest Scale

该奖项由引力物理和原子、分子和光学实验物理项目支持。在微观距离上理解引力的本质是基础物理学中最重要的开放问题之一。尽管广义相对论为描述大范围的引力效应提供了一个经过极好测试的框架，但它不能与粒子物理的标准模型相结合，以提供小尺度下的引力描述。发展可以并入标准模型的量子引力理论是基础物理的核心目标，对我们理解粒子物理和似乎弥漫在宇宙中的“暗能量”的神秘本质有着广泛的影响。许多试图为重力提供一致的微观框架的理论(例如，那些涉及额外维度的理论)预测，重力可能在距离小于1毫米时偏离熟悉的平方反比定律。由于微小距离的引力相互作用的强度很小，这种偏差很难通过实验测量。这里描述的研究试图通过一种新颖的实验装置来深入了解微观引力的领域。此外，这项研究还将加强对STEM领域学生的培训，这些领域对国家的未来至关重要。以前在这些距离尺度上的测量采用了源于真人大小的设备的技术，其中使用机械弹簧作为力传感器。该小组开发了一项全新的技术，利用激光的光场来限制和测量微米(或最终亚微米)大小的石英微球的运动。该小组之前进行的研究包括迄今为止最灵敏的搜索，寻找比电子电荷小4个数量级以上的分数电荷。这是不得不释放微球并检查它们是否真的是中性的副产品。该小组已经完成了一个新的陷阱的建造，在这个陷阱中，整个微球的位置读出是以干涉测量的方式进行的。这在这一研究领域是第一次，并将适用于其他领域，例如生物学或聚合物科学。这笔资金支持的研究包括探索旋转微球的可能性，这可能会减少重力测量的背景，还可能导致纳米陀螺仪的发展。这一奖项反映了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。

This award is supported by the Gravitational Physics and the Atomic, Molecular and Optical Experimental Physics programs. Understanding the nature of gravity at microscopic distances is one of the most important open problems in fundamental physics. Although General Relativity provides an extremely well-tested framework for describing gravitational effects at large distances, it cannot be consistently combined with the Standard Model of particle physics to provide a description of gravity at small scales. The development of a quantum theory of gravity that can be incorporated into the Standard Model is a central goal of fundamental physics, with broad implications for our understanding of particle physics and the mysterious nature of the "dark energy" that appears to permeate the universe. Many theories attempting to provide a consistent microscopic framework for gravity (e.g., those involving extra dimensions) predict that gravity could deviate from the familiar inverse square law at distances shorter than a mm. Such deviations are extremely difficult to measure experimentally due to the small strength of gravitational interactions at microscopic distances. The studies described here attempt to gain insights into the realm of microscopic gravitational forces with a novel experimental setup. Additionally, the research will enhance the training of students in STEM areas which are vital for the future of the nation.Previous measurements at these distance scales have employed techniques derived from human-size devices in which mechanical springs are used as force sensors. This group has developed a drastically new technique, using the light field of a laser to confine and measure the motion of micron (or, eventually, submicron)-size quartz microsphere. Previous studies undertaken by this group include the most sensitive search to date for fractional charges over 4 orders of magnitude smaller than the charge of an electron. This is a by-product of having to discharge the microspheres and check that they are really neutral. The group has completed the construction of a new trap in which the entire microsphere position readout is carried out interferometrically. This is a first in this area of research and will be applicable to other areas, e.g. biology or polymer science. The studies supported by this grant include exploring the possibility of spinning the microspheres, something that could reduce the background of the gravity measurements and may also lead to the development of nanogyroscopes.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.