Topology of circular orbits for charged particles around multi-horizon black holes

The study of the topological properties of circular orbits is opening up new perspectives for exploring the spacetime structure around black holes. In this work, we investigate how the charged properties of particles affect the topological characteristics of circular orbits for charged test particles in asymptotically flat, AdS, and dS black holes. Our findings demonstrate that the charged properties not only influence the topological properties of timelike circular orbits but also impact those of null circular orbits. Additionally, we explore scenarios involving multiple horizons and find that for a multi-horizon black hole, if a circular orbit with fixed angular momentum and charge can exist between two neighboring horizons, there will always be at least one unstable null circular orbit and one unstable timelike circular orbit.