Cosmic fluctuations and dark matter from scalar field oscillations.

It is argued that scale-invariant cosmic uctuations and cosmic dark matter might originate from two di erent modes of a single scalar eld. The dynamical relaxation of a multicomponent classical scalar eld in an expanding universe excites two generic types of global modes: massless Goldstone oscillations, which lead to scale-invariant isentropic uctuations, and massive Higgs modes, which lead to cold dark matter with isocurvature uctuations in density. Estimates are given of these e ects in a simple generic model where the large scale uctuations and dark matter density match those observed; it is shown that the former requires a heavy scale ( 0 10 16GeV) for the potential minimum, and the latter requires an extremely small self coupling ( 10 83). An additional prediction of the model is then the formation of isocurvature uctuations, leading to the early collapse of dense 100M dark matter \miniclusters", formation of dense halos on the scale of compact dwarf galaxies, and possibly observable gravitational microlensing of quasars.