Optical atomic magnetometer networks to search for exotic physics

Abstract

A host of astrophysical and cosmological measurements have established that the majority of matter in the Universe is dark matter. Understanding its nature is of paramount importance to astrophysics, cosmology, and particle physics. A well-motivated possibility is that the dark matter consists of ultralight bosons such as axions, with masses far smaller than 1 eV, in which case they are well-described as a classical field. Due to topology or self-interactions, ultralight bosonic fields can form stable, macroscopic configurations in the form of boson stars or topological defects (domain walls). Even in the absence of topological defects or self-interactions, bosonic dark matter fields exhibit stochastic fluctuations. Furthermore, cataclysmic astrophysical events (like black hole mergers) could produce intense bursts of exotic low-mass fields (ELFs). In any of these scenarios, instead of being bathed in a uniform flux, terrestrial detectors will witness transient events when the exotic bosonic fields pass through Earth. The Global Network of Optical Magnetometers to search for Exotic physics (GNOME): an international collaboration to search for such transient events with a worldwide network of more than a dozen time-synchronized optical atomic magnetometers, with stations in Europe, North America, Asia, the Middle East, and Australia. We will report on our latest results and future directions.