New Torsion Balance Technique to Test Gravity at Short Distances

该奖项支持对一种新方法的初步研究，该方法可以在长度尺度小于100微米的范围内测试牛顿引力定律。最近的理论建议，包括统一场景，额外维度，以及涉及暗能量的宇宙学考虑，都涉及到牛顿引力在短距离内崩溃的可能性。PI和其他人之前发表的结果描述了使用带有孔阵列的扭转摆将这种击穿的上限描述为大约100微米。新方法使用了一种不同的真零实验，用一种简单但高效的几何体来探测在更短的距离内违反牛顿引力的情况。垂直板扭转摆将与吸引板平行悬挂，从而产生均匀的引力场。当这个盘朝向和远离钟摆移动时，如果牛顿引力成立，摆上的力不会改变。为了最大限度地提高钟摆对牛顿引力违例的敏感度，它是由一个在密度分布中有一个台阶的平板制成的，这样平板的一半质量比另一半更接近吸引子。为了避免静电和残余气体产生的作用力，在吸引器和钟摆之间的空间放置了一层薄的金属薄膜。这项实验是使用现有扭转天平进行测试的另一种方法，具有完全不同的系统不确定性，并有可能测试小至20微米的长度尺度的重力。该奖项将支持研究生建造科学仪器并进行极具挑战性的测量，在实验物理和科学研究的所有方面提供出色的培训。这种新方法涉及许多技术创新，可能会在其他领域得到应用，如重力波检测。

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.