Low-mass boson dark matter particles produced after the Big Bang
form a classical field and/or topological defects. Effects produced
by the interaction of ordinary matter with dark matter may be first
power in the underlying interaction strength rather than the second
power. This may give a big advantage, since the dark matter
interaction constant is extremely small. Limits on certain types of
dark matter have been improved up to 15 orders of magnitude. New
experiments are proposed.