Possible Relics from New Physics in the Early Universe: Inflation, the Cosmic Microwave Background, and Particle Dark Matter

I review two different connections between particle theory and early-Universe cosmology: (1) Cosmic-microwave-background (CMB) tests of inflation and (2) particle dark matter. The inflationary predictions of a flat Universe and a nearly scale-invariant spectrum of primordial density perturbations will be tested precisely with forthcoming maps of the CMB temperature. A stochastic gravitational-wave background may be probed with a map of the CMB polarization. I also discuss some other uses of CMB maps. Particle theory has produced two very well-motivated candidates for the dark matter in the Universe: an axion and a supersymmetric particle. In both cases, there are a variety of experiments afoot to detect these particles. I review the properties of these dark-matter candidates and these detection techniques. Much of the material here has appeared before in astro-ph/9712215 and hep-ph/9710467, but the article here is updated and also expanded considerably.