Searching for axion stars and Q-balls with a terrestrial magnetometer network

Understand

Light (pseudo-)scalar fields are promising candidates to be the dark matter in the Universe.

• Under certain initial conditions in the early Universe and/or with certain types of self-interactions, they can form compact dark-matter objects such as axion stars or Q-balls.
• Direct encounters with such objects can be searched for by using a global network of atomic magnetometers.
• It is shown that for a range of masses and radii not ruled out by existing observations, the terrestrial encounter rate with axion stars or Q-balls can be sufficiently high (at least once per year) for a detection.