Axion superradiance in rotating neutron stars

Understand

It is a well-known fact that compact gravitating objects admit bound state configurations for massive bosonic fields.

• In this work we describe a new class of superradiant instabilities of axion bound states in neutron star magnetospheres.
• The instability arises from the mixing of axion 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 absorbative horizon, the non-hermitian dynamics in this paper come from the resistivity in the stellar magnetosphere arising from a finite bulk conductivity.