A Simple Varying-alpha Cosmology

Abstract

We investigate the cosmological consequences of a simple theory in which the electric charge \(e\) is allowed to vary. The theory is locally gauge and Lorentz invariant, and satisfies general covariance. We find that in this theory the fine structure 'constant', \(\alpha \), remains almost constant in the radiation era, undergoes small increase in the matter era, but approaches a constant value when the universe starts accelerating because of the presence of a positive cosmological constant. This model satisfies geonuclear, nucleosynthesis, and CMB constraints on time-variation in \(\alpha \), while fitting simultaneously the observed accelerating universe and the recent high-redshift evidence for small \(\alpha \) variations in quasar spectra. The model also places specific restrictions on the nature of the dark matter. Further tests, involving stellar spectra and the E\"otv\"os experiment, are proposed.