Plasma-photon interaction in curved spacetime: Formalism and quasibound states around nonspinning black holes

We investigate the linear dynamics of an electromagnetic field propagating in curved spacetime presence plasma. The dynamical equations are generically more involved and richer than effective Proca equation adopted as a model previous work. discuss general focus on case cold plasma background spherically-symmetric black hole, showing that system admits plasma-driven, quasibound states prone to become superradiantly unstable when hole rotates. different from those have some similarities with massive scalar field, suggesting instability can be strongly suppressed compared estimates. Our framework provides first step towards full understanding plasma-photon interactions around astrophysical holes.