Bounds on the minimum orbital periods of non-singular Hayward and Bardeen black holes

Abstract: Based on previous studies, universal bounds $4\pi M \leqslant T_{min} \leqslant 6\sqrt{3}\pi M$ were conjectured to be characteristic properties of black hole spacetimes, where $M$ represents the mass of black holes and $T_{min}$ is the minimum orbital periods around black holes. In this work, we explore the minimum orbital periods of objects around Hayward and Bardeen black holes without central singularities. By combining analytical and numerical methods, we show that both Hayward and Bardeen black holes conform to these bounds. Our results imply that such bounds may be connected to the presence of the black hole horizon rather than the singularity.