  The origin of dark matter in the universe may be scalar particles produced by
amplification of quantum fluctuations during a period of dilaton-driven
inflation. We show, for the first time, that a single species of particles,
depending on its mass and interactions, can be a source of both cold and hot
dark matter simultaneously. Detection of such weakly interacting particles with
masses below a fraction of an eV presents a new challenge for dark matter
searches.
