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

University Of Washington, Seattle WA

Investigators

Abstract

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.