Neutron Stars as Axion Laboratories

by Samuel Witte (University of Barcelona)

Wednesday 26 Apr 2023, 14:30 → 15:30 Europe/Rome

1/1-2 - Aula "C. Voci" (Dipartimento di Fisica e Astronomia - Edificio Marzolo)

Axions are hypothetical well-motivated particles whose presence could explain a number of outstanding questions in physics today, including the lack of charge-parity violation in the strong interaction and the existence of dark matter. In this talk I will argue that the magnetospheres of neutron stars present a particularly compelling environment in which to look for axions — here, one can find the largest known magnetic fields in the Universe, and a dilute plasma capable of triggering a resonant enhancement of the axion-photon mixing. In effect, neutron star magnetospheres can take what are conventionally considered feebly interacting particles and turn them into strongly interacting particles. I will discuss a variety of signatures that can arise from these systems, including the production of radio spectral lines and broadband radio emission, short and long-term transient radio events, and pulsar nulling.  I will also comment on the status of current and future searches for these signatures, showing that these techniques can be used to test the existence of axions across a wide range of parameter space, including parts of the parameter space where the QCD axion can comprise the entirety of dark matter.