Particle motions around regular black holes

TL;DR

This paper explores the dynamics of particles and photons around regular black holes, revealing stable and unstable orbits, charge effects, and photon behavior inside the horizon, with implications for understanding black hole spacetime structure.

Contribution

It provides new insights into particle and photon orbits around regular black holes, including the existence of photon orbits inside the horizon and charge-dependent orbital characteristics.

Findings

Existence of stable and unstable circular orbits for massive particles.

Unstable photon orbit found inside the event horizon.

Charge influences the radius of the innermost stable circular orbit and the periapsis shift.

Abstract

We investigate the bound orbits of massive/massless, neutral particles and photons moving around regular black holes of Fan and Wang. For massive particles, we show the existence of stable/unstable circular orbits and the charge dependence of the radius of the innermost stable circular orbit. Remarkably, we find an unstable circular orbit of photons inside the event horizon. For massless particles and photons, we show that both stable and unstable circular orbits can exist in a regular and horizonless spacetime with a slight overcharge. Then, we also discuss the periapsis shift of massive neutral particles orbiting around the black hole, and show that the charge gives a negative correction to the shift for black holes with small nonlinearity of electrodynamics.