New Torsion Balance Technique to Test Gravity at Short Distances

该奖项支持在长度尺度小于100微米的情况下测试牛顿引力定律的新方法的初步研究。最近的理论建议，包括统一的情况下，额外的维度，和宇宙学的考虑，涉及暗能量都涉及到一个短期的牛顿引力崩溃的可能性。PI和其他人先前发表的结果描述了使用具有孔阵列的扭摆在约100微米处的这种击穿的上限。新方法使用了一种不同的真零实验，具有简单但高效的几何结构，旨在在更短的距离内检测牛顿引力的违反。一个垂直的平板扭摆平行于一个吸引板悬挂，吸引板产生一个均匀的引力场。当这个板移向和移离钟摆时，如果牛顿引力成立，钟摆上的力不会改变。为了最大限度地提高钟摆对违反牛顿引力的敏感性，它是由密度分布有台阶的板制成的，这样板的一半质量比另一半更接近吸引子。为了避免由于静电和残余气体而产生的力，在吸引子和摆之间的空间中放置了薄金属膜。该实验是使用现有扭力天平进行测试的替代方法，具有完全不同的系统不确定性，并且有可能在小至20微米的长度尺度上测试重力。该奖项将支持研究生建造科学仪器并进行非常具有挑战性的测量，在实验物理和科学研究的各个方面提供出色的培训。新方法涉及许多技术创新，可能会在其他领域（如重力波探测）中找到应用。

This award supports preliminary research on a new method to test Newton's law of gravity at length scales shorter than 100 micrometers. Recent theoretical suggestions including unification scenarios, extra dimensions, and cosmological considerations involving dark energy all involve the possibility of a breakdown of Newtonian gravity for short ranges. Previously published results by the PI and others described upper limits to such a breakdown at around 100 micrometers using a torsion pendulum with an array of holes. The new method uses a different true null-experiment with a simple, yet highly efficient geometry designed to detect violations of Newtonian gravity at much shorter distances. A vertical plate torsion pendulum will hang parallel to an attractor plate which generates a uniform gravitational field. As this plate is moved toward and away from the pendulum, the forces on the pendulum will not change if Newtonian gravity holds. To maximize the pendulum's sensitivity to violations of Newtonian gravity, it is made from a plate with a step in its density profile, so that one half of the plate's mass is closer to the attractor than the other. To avoid forces due to electrostatics and residual gas, a thin metallic membrane is placed in the space between the attractor and the pendulum. This experiment is an alternative approach to test using existing torsion balances, with entirely different systematic uncertainties and the potential to test gravity at length scales as small as 20 micrometers. This award will support graduate students to build a scientific instrument and conduct a very challenging measurement, providing excellent training in all the aspects of experimental physics and scientific research. The new method involves many technical innovations that may find applications in other areas such as gravity-wave detection.