Low-Energy Probes of the Gravity/Particle-Physics Frontier

这个项目的目的是开发高灵敏度的扭转平衡仪器，以寻找几种现代理论试图将重力与其他物理力统一起来所预测的超弱力。这种统一面临着两个深层次的问题：与其他已知力相比，引力的极端微弱，以及观测到的宇宙学常数与真空能量密度的量子力学预测之间的巨大差距。克服这些问题的理论想法往往预示着新的引力现象，可以用改进的仪器进行测试。特别是，牛顿的平方反比引力定律将被测试到比人类头发直径小得多的长度尺度，以探索更大的额外维度，并测试对所观察到的宇宙常数微小的可能解释。爱因斯坦等效原理对各种物质的测试灵敏度将提高30倍，以测试对神秘暗能量来源的猜测，这种神秘的暗能量似乎占宇宙总质量能量的三分之二。一种包含近一摩尔极化电子的特殊扭转摆将被用来以极高的灵敏度搜索冻结在宇宙中的矢量场，这些矢量场可能导致宏观上破坏电荷-宇称-时间反转(CPT)对称性。最后，将开发一种新型的扭转平衡仪器来研究尚未观测到的轴子所产生的力。

The purpose of this project is to develop highly sensitive torsion-balance instruments to search for the ultra-weak forces predicted by several modern theoretical attempts to unify gravity with the other forces of physics. This unification is faced with two deep problems: the extreme weakness of gravity compared to the other known forces, and the enormous observed disparity between the cosmological constant and the quantum-mechanical predictions of the vacuum-energy density. Theoretical ideas for overcoming these problems often predict new gravitational phenomena that can be tested with improved instruments. In particular, Newton's inverse-square law of gravitation will be tested down to length scales substantially smaller than the diameter of a human hair to probe for large extra dimensions and to test a possible explanation for the observed smallness of the cosmological constant. The sensitivity of tests of Einstein's Equivalence Principle for a variety of materials will be increased by a factor of 30 to test speculations about the source of the mysterious dark energy that appears to comprise two thirds of the total mass-energy of the Universe. A special torsion pendulum that contains almost a mole of polarized electrons will be used to search, with great sensitivity, for vector fields frozen into the universe that could cause macroscopic violation of charge-parity-time reversal (CPT) symmetry. Finally, a novel torsion-balance instrument will be developed to search for the force produced by the as yet unobserved axion.