A NEW DARK-MATTER CANDIDATE - KALUZA-KLEIN SOLITONS

Background radiation has recently provided some strong constraints on conventional candidates for dark matter, which leads us to suggest ano ther possibility: Kaluza-Klein solitons. These are the analogs of blac k holes in the simplest extension of general relativity from four to f ive dimensions, a theory which is otherwise in agreement with astrophy sical data. We outline the essential properties of such solitons, whic h resemble balls of radiation-like matter. Information on solitons can be obtained from background radiation, the morphologies of galaxies, and gravitational lensing.