Cataclysmic astrophysical events such as black hole mergers could release energy in unexpected forms. Exotic low-mass fields (ELFs), for example, could propagate through space and cause feeble signals detectable with quantum sensor networks such as the atomic clocks of the GPS network or the magnetometers of the GNOME network. These are the results of theoretical calculations undertaken by a research group including Dr. Arne Wickenbrock of the PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU) and the Helmholtz Institute Mainz (HIM). They are particularly interesting in the context of the search for dark matter, as low-mass fields are regarded as promising candidates for this exotic form of matter.
From multi-messenger astronomy to the search for dark matter
Multi-messenger astronomy involves the coordinated observation of disparate signals that stem from the same astrophysical event. Since the first detection of gravitational waves with the LIGO interferometer several years ago, the interest in this field has expanded enormously and it has yielded a tremendous amount of new information originating from the depths of the universe. "When gravitational waves are generated somewhere in space and detected on Earth, numerous telescopes now focus on the event to record various signals, such as those in the form of electromagnetic radiation, for instance," explains Arne Wickenbrock. "We asked ourselves what would happen if part of the observed energy released by such events was also radiated in the form of exotic low-mass fields or ELFs. Would we be able to detect them with our existing networks of quantum sensors?"
The scientists' calculations have confirmed that this could be the case for certain parameters. "We also reasoned that such fields, when radiated, would cause a characteristic frequency signature in the networks," adds Arne Wickenbrock. "The signal would be similar to the sound of a passing siren, sweeping from high to low frequencies." The researchers have two particular networks in mind: the worldwide GPS network of atomic clocks and the GNOME network, which is comprised of a multitude of magnetometers distributed around the globe. On the basis of the expected strength of the signal, the GPS system should currently be sensitive enough to detect ELFs. The work group of JGU Professor Dmitry Budker at HIM, together with other teams, is currently upgrading the GNOME network, and on completion this should also be sensitive enough to observe such events.
Potential ELFs are of particular significance in the search for dark matter. Although we know this strange form of matter must exist, nobody yet knows what it is made of. Specialists are considering and researching a whole range of possible particles that might theoretically qualify as candidates. Among the most promising current candidates are extremely light bosonic particles, which can also be seen in terms of a classic field oscillating at a particular frequency. "Thus, in the depths of the universe, dark matter in the form of ELFs may be created during the merger of two black holes," concludes Arne Wickenbrock. "Precision quantum sensor networks, in turn, could function as ELF telescopes, adding another important element to the toolbox of multi-messenger astronomy."