New Torsion Balance Technique to Test Gravity at Short Distances

该奖项支持一项新方法的初步研究，该方法可以在小于100微米的长度尺度上测试牛顿万有引力定律。最近的理论建议包括统一场景、额外维度和涉及暗能量的宇宙学考虑，都涉及到短期内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带有一系列孔的扭摆在大约100微米处发生这种击穿的上限。新方法使用了一种不同的真正的零实验，它采用了一种简单但高效的几何结构，旨在检测更短距离内牛顿引力的违反。一个垂直板扭摆将与一个产生均匀引力场的吸引板平行悬挂。如果牛顿引力成立，当这块板靠近或远离钟摆时，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灵敏度，钟摆是由一块密度剖面上有一个台阶的板制成的，这样一来，这块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力，在吸引器和钟摆之间的空间放置了一层薄薄的金属膜。该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立科学仪器并进行极具挑战性的测量，为实验物理和科学研究的各个方面提供优秀的培训。这种新方法涉及许多技术创新，可能会在引力波探测等其他领域得到应用。

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.