A Cosmologist's Tour through the New Particle Zoo (Candy Shop?)

Abstract

Recent developments in elementary particle physics have led to a renaissance in cosmology, in general, and in the study of structure formation, in particular. Already, the study of the very early (t ≤ 10−2 sec) history of the Universe has provided valuable hints as to the ‘initial data’ for the structure formation problem — the nature and origin of the primeval density inhomogeneities, the quantity and composition of matter in the Universe today, and numerous candidates for the constituents of the ubiquitious dark matter. I review the multitude of WIMP candidates for the dark matter provided by modern particle physics theories, putting them into context by briefly discussing the theories which predict them. I also review their various birth sites and birth processes in the early Universe. At present the most promising candidates seem to be a 30 or so eV neutrino, a few GeV photino, or the ‘invisible axion’ (weighing in at about 10−5 eV!), with a planck mass monopole, quark nuggets, and shadow matter as the leading ‘dark’ horse candidates. I also mention some very exotic possibilities — unstable WIMPs, cosmic strings, and even the possibility of a relic cosmological term.