Physics & Astronomy Colloquium

3:30 PM, Friday, March 30, 2007
Room 155, Chem-Phys Building

Dr. Ricardo S. Decca
Department of Physics
Indiana University - Purdue University Indianapolis

"Newton, Casimir, and hypothetical forces''

In this Colloquium a discussion on the search for ``new forces'' will be presented. These interactions could directly affect the strength of gravity at small separations. Using Cavendish-like experiments, many groups are trying to observe these deviations. In our group we work in the Casimir regime, loosely defined as when the separation between the test masses is ~200 nm, i.e. when the Casimir force becomes the dominant background. The first topics that will be discussed are how to get precise measurements, and why they are important. In particular, our measurements are precise enough to make possible a distinction among different predictions about the thermal dependence of the Casimir interaction.

The second part of the talk deals specifically with the search for hypothetical forces at small separation between the test bodies. Since the Casimir force (of strength ~10 pN for our configuration) is too large a background (the Newtonian gravitational force is ~ 10 zN for the same configuration), it is better to perform a completely different experiment where the effect of the Casimir interaction is minimized (which we call a Casimir-less experiment). I will introduce our experimental setup, which yields ~ 6 fN/Hz1/2 sensitivity. The current status in the search for hypothetical forces, and how much we expect to constrain parameter space with our approach will be presented.

Refreshments will be served in CP 179 at 3:15 PM