Searching for Scalar Dark Matter in Atoms and Astrophysical Phenomena: Variation of Fundamental Constants

We propose to search for scalar dark matter via its effects on theelectromagnetic fine-structure constant and particle masses. Scalar dark matterthat forms an oscillating classical field produces `slow' linear-in-time driftsand oscillating variations of the fundamental constants, while scalar darkmatter that forms topological defects produces transient-in-time variations ofthe constants of Nature. These variations can be sought for with atomic clock,laser interferometer and pulsar timing measurements. Atomic spectroscopy andBig Bang nucleosynthesis measurements already give improved bounds on thequadratic interaction parameters of scalar dark matter with the photon,electron, and light quarks by up to 15 orders of magnitude, while Big Bangnucleosynthesis measurements provide the first such constraints on theinteraction parameters of scalar dark matter with the massive vector bosons