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Abstract Numerous theories extending beyond the standard model of particle physics predict the existence of bosons that could constitute dark matter. In the standard halo model of galactic dark matter, the velocity distribution of the bosonic dark matter field defines a characteristic coherence time τ c . Until recently, laboratory experiments searching for bosonic dark matter fields have been in the regime where the measurement time T significantly exceeds τ c , so null results have been interpreted by assuming a bosonic field amplitude Φ 0 fixed by the average local dark matter density. Here we show that experiments operating in the T  ≪  τ c regime do not sample the full distribution of bosonic dark matter field amplitudes and therefore it is incorrect to assume a fixed value of Φ 0 when inferring constraints. Instead, in order to interpret laboratory measurements (even in the event of a discovery), it is necessary to account for the stochastic nature of such a virialized ultralight field. The constraints inferred from several previous null experiments searching for ultralight bosonic dark matter were overestimated by factors ranging from 3 to 10 depending on experimental details, model assumptions, and choice of inference framework. 

Abstract Ultralight bosons such as axion-like particles are viable candidates for dark matter. They can form stable, macroscopic field configurations in the form of topological defects that could concentrate the dark matter density into many distinct, compact spatial regions that are small compared with the Galaxy but much larger than the Earth. Here we report the results of the search for transient signals from the domain walls of axion-like particles by using the global network of optical magnetometers for exotic (GNOME) physics searches. We search the data, consisting of correlated measurements from optical atomic magnetometers located in laboratories all over the world, for patterns of signals propagating through the network consistent with domain walls. The analysis of these data from a continuous month-long operation of GNOME finds no statistically significant signals, thus placing experimental constraints on such dark matter scenarios. 

Numerous observations suggest that there exist undiscovered beyond‐the‐standard‐model particles and fields. Because of their unknown nature, these exotic particles and fields could interact with standard model particles in many different ways and assume a variety of possible configurations. Here, an overview of the global network of optical magnetometers for exotic physics searches (GNOME), the ongoing experimental program designed to test a wide range of exotic physics scenarios, is presented. The GNOME experiment utilizes a worldwide network of shielded atomic magnetometers (and, more recently, comagnetometers) to search for spatially and temporally correlated signals due to torques on atomic spins from exotic fields of astrophysical origin. The temporal characteristics of a variety of possible signals currently under investigation such as those from topological defect dark matter (axion‐like particle domain walls), axion‐like particle stars, solitons of complex‐valued scalar fields (Q‐balls), stochastic fluctuations of bosonic dark matter fields, a solar axion‐like particle halo, and bursts of ultralight bosonic fields produced by cataclysmic astrophysical events such as binary black hole mergers are surveyed.