Axions: From Magnetars and Neutron Star Mergers to Beam Dumps and BECs

Understand

We review topics in searches for axion-like-particles (ALPs), covering material that is complementary to other recent reviews.

• The first half of our review covers ALPs in the extreme environments of neutron star cores, the magnetospheres of highly magnetized neutron stars (magnetars), and in neutron star mergers.
• The focus is on possible signals of ALPs in the photon spectrum of neutron stars and gravitational wave/electromagnetic signals from neutron star mergers.
• We then review recent developments in laboratory-produced ALP searches, focusing mainly on accelerator-based facilities including beam-dump type experiments and collider experiments.