Abstract

The extreme magnetic fields and high spin of neutron stars make them an exciting environment in which to probe rotational instabilities driven by the coupling of electromagnetism to new sectors beyond the Standard Model. In this talk I describe a new class of superradiant instabilities in which ultralight scalar fields extract rotational energy from neutron stars. The instability arises from the mixing of scalar and photon modes in the magnetic field of the neutron star which extract energy from the rotating magnetosphere. Unlike for black holes, where the dissipation required for superradiance is provided by an absorptive horizon, the non-hermitian dynamics in this setup comes from the resistivity in the stellar magnetosphere. This leads to the exponential growth of the scalar field profile around the star corresponding to complex eigenfrequencies. The instability rate can then be compared to the characteristic astrophysical time scales of neutron stars given by their spin-down times.

The slides of the presentation can be found here