Time Variation of Fundamental Constants as a Probe of New Physics

There has recently been reported evidence for a possible time variation of the fine structure constant on cosmological time scales . Such variations are not surprising in any theoretical framework for the unification of basic forces involving extra dimensions or in which dimensionless couplings are related to the expectation values of scalar fields. However, the variation of α is likely to be correlated with the variations in other fundamental quantities, such as other gauge and Yukawa couplings, and the ratios of such dimensionful scales as the unification and electroweak or supersymmetrybreaking scales, or the unification and gravity scales. Thus, the observation of such variations is a powerful probe of the underlying physics. I briefly summarize relevant issues and describe an analysis and parametrization of these effects done in collaboration with Matt Strassler and Gino Segrè .