We have two projects in our laboratory that are suitable for participation of undergraduates, either as honors thesis projects or as summer research projects. Students interested in summer research should contact me before April 1.

We have recently begun a new experiment to measure the electron electric-dipole moment (edm) using a solid-state system. The existence of a permanent electron edm violates both time-reversal symmetry and parity. The present limits on the electron edm come from an atomic beam experiment recently completed in Berkeley. Recent theoretical and experimental investigations suggest that precision voltage measurements across a magnetizable dielectric system (gadolinium-iron garnet) at liquid-nitrogen temperature should permit measurement of the electron edm with a precision one hundred times greater than has been possible with the atomic systems. Construction of the first apparatus to allow such a measurement should be completed before summer. The project will consist of learning to use this apparatus to make the measurement and the investigation of possible systematic effects that might mimic the edm signal. If successful, this project will have profound implications for various particle theories that include physics beyond the "standard model", especially supersymmetry. The project is an interesting blend of electrodynamics, atomic physics, particle physics, solid-state physics and low-temperature physics.

We also have a project underway to test Einstein's postulate of Local Lorentz Invariance (LLI). An earlier version of this experiment done here at Amherst (C.J. Berglund, L.R. Hunter, D. Krause, Jr., E.O. Prigge, and M.S. Ronfeldt, Phys. Rev. Lett. 75, 1879 (1995)) established what was at that time one of the best experimental tests of the validity of this postulate. Since the publication of this work, it has been shown that the experiment also establishes one of the best tests of CPT (charge, parity and time) invariance, one of the cornerstones of modern physics. It was shown that this is one of the few experiments with adequate sensitivity to explore physics at the Planck scale. The experiment compares the relative frequencies of mercury and cesium light-absorption magnetometers as a function of the direction of the applied magnetic field with respect to a preferred direction in space. In the old measurement, the change in the magnetic field direction was achieved solely through the rotation of the earth. This required that all of the experimental parameters be held constant for a period of several days. We envision two improvements to this apparatus. First, we intend to replace the mercury discharge lamp with a quadrupled diode laser that generates the optical pumping light at 254 nm. The laser, which is now operational, should have better long-term stability than the lamp. The second improvement involves mounting the entire apparatus on a rotation stage, so that the direction of the magnetic field can be modulated every six minutes, rather than every 24 hours. This higher modulation frequency should result in a dramatic reduction in the system noise. We believe that these two changes should significantly improve the sensitivity of this experiment, by perhaps as much as two orders of magnitude. This new experiment would then provide one of the most stringent tests of both LLI and CPT, two of the most important fundamental symmetries of nature.