Exploring a Low-energy Frontier of Particle Physics Using Methods of Experimental Gravitation

这个项目的目标是对重力自由落体的普遍性进行更精确和更普遍的测试。 标准的经典引力理论，广义相对论，将自由落体的普遍性作为关于引力的精确陈述。 然而，这一原理是否准确成立，则是一个实验性的问题。 检验这一原则有两个强有力的理由。 首先，广义相对论不是一个量子力学理论，目前关于引力的量子力学理论的一些观点预测了自由落体的普遍性会受到来自额外的“引力”标量场或矢量场的破坏。 其次，通过寻找经典引力所认为的对称性的破坏，人们可以探索新的、超弱的、非引力的力。 因为不可能屏蔽引力场，所以这种超弱力通常隐藏在引力之下。 但是任何新的力都可能违反自由落体的普适性，因此即使它比引力弱得多，也可以被检测到。 拟议中的试验要求继续开发改进的仪器，以测量不同材料被吸引到地球、巨大的铀实验室源或天文结构的加速度的微小差异。 将采用三种不同的扭转平衡仪器。 其中两个是在以前的NSF支持下开发的，将升级用于拟议的测试，并将建造一个新的更灵敏的仪器。 这些仪器的组合将允许测试从1厘米到无穷大的长度尺度上的自由落体的普遍性。 特别是，将有可能测试重力是否是普通物质和宇宙暗物质之间的主导远程力;并且，结合现有的月球激光测距数据，对引力进行“无环孔”测试引力结合能的引力性质。 最后一项测试将通过比较月球和地壳的“比例模型”朝向太阳的加速度来进行。

The goals of this project are to make more precise and more general tests of the Universality of Gravitational Free Fall. The standard, classical theory of gravity, General Relativity, incorporates the Universality of Free Fall as an exact statement about gravity. It is an experimental question, however, if this principle holds exactly. There are two strong reasons for testing the principle. First, General Relativity is not a quantum mechanical theory and some current ideas about possible quantum-mechanical theories of gravity predict violations of the Universality of Free Fall arising from additional `gravitational` scalar or vector fields. Second, by searching for violations of a symmetry that classical gravity holds to be exact, one can probe for new, ultra-weak, non-gravitational forces. Because it is impossible to shield a gravitational field, such ultra-weak forces would normally lie hidden `underneath gravity`. But any new force is expected to violate the Universality of Free Fall and so can be detected even if it is much weaker than gravity. The proposed tests require the continued development of improved instruments for measuring tiny differences in the accelerations of different materials attracted toward the earth, toward a massive Uranium laboratory source, or to astronomical structures. Three different torsion-balance instruments will be employed. Two of them, developed under previous NSF support, will be upgraded for the proposed tests, and a new more sensitive instrument will be constructed. The combination of these instruments will permit tests of the Universality of Free Fall over length scales ranging from 1 cm to infinity. In particular, it will be possible to test whether gravity is the dominant long-range force between ordinary mater and the cosmological dark matter; and, in conjunction with existing data on lunar laser-ranging, to make a `loop-hole free` test of the gravitational properties of gravitational binding energy. This last test will be performed by comparing the accelerations toward the sun of `scale models` of the Moon and the Earth's crust.