How do you know if you ran through a wall?

Understand

Stable topological defects of light (pseudo)scalar fields can contribute to the Universe's dark energy and dark matter.

• Currently the combination of gravitational and cosmological constraints provides the best limits on such a possibility.
• We take an example of domain walls generated by an axion-like field with a coupling to the spins of standard-model particles, and show that if the galactic environment contains a network of such walls, terrestrial experiments aimed at detection of wall-crossing events are realistic.
• In particular, a geographically separated but time-synchronized network of sensitive atomic magnetometers can detect a wall crossing and probe a range of model parameters currently unconstrained by astrophysical observations and gravitational experiments.