The boson dark matter particles produced after Big Bang may form a Bose condensate and/or topological defects. In contrast to traditional dark matter searches, effects produced by interaction of an ordinary matter with this condensate and defects may be first power in the underlying interaction strength, which is extremely small, rather than the second power or higher (which appears in a traditional search for the dark matter).
We discuss new effects and schemes for the direct detection of dark matter, including axions, axion-like pseudoscalar particles (ALPs) and scalar particles, as well as topological defects. Specific effects produced by the particle condensates include space-time variation of the fundamental constants (fine structure constant alpha, particle masses, etc) including both slow variation (on the cosmological scale) and fast oscillations. Topological defects may also produce transient and correlated observable effects.
In addition to traditional methods to search for the variation (atomic clocks, quasar spectra, Big Bang Nucleosynthesis, etc) we discuss variations in phase shifts produced in laser/maser interferometers (such as LIGO, Virgo, GEO600 and TAMA300), changes in pulsar rotational frequencies (which may have been observed already in pulsar glitches), non-gravitational lensing of cosmic radiation and the time-delay of pulsar signals, as well as changes in the rate of Earth rotation.
Other effects of dark matter include oscillating or transient atomic electric dipole moments, precession of electron and nuclear spins about the direction of Earth’s motion through an axion/ALP condensate (the axion wind effect), and axion-mediated spin-gravity couplings.
The proposed detection methods offer sensitive probes into important, unconstrained regions of dark matter parameter spaces.