“Torsion Balance Experiments: A Low-Energy Frontier of Particle Physics”, 2009 (; backlinks):
We review recent mechanical experiments that test some of the most basic principles of physics including the weak and strong forms of the Equivalence Principle, the gravitational inverse-square law, and Lorentz invariance. The very high sensitivity of these tests allows one to place interesting constraints on string-theory inspired conjectures about new Yukawa forces from the exchange of very light scalar, pseudo-scalar or vector particles, large extra dimensions, the chameleon mechanism, non-commutative spacetime geometry, and Planck-scale Lorentz violation.
[Keywords: torsion balance, equivalence principle, inverse square law, Lorentz invariance]