Anomalous changing of geodesics in hairy black holes

Abstract

We study the motion of test particles and the propagation of light around neutral hairy black holes under the influence of a self-interacting real scalar field minimally coupled to gravity. It is highly relevant in the context of recent observations of the Event Horizon Telescope: The Shadow of the supermassive Black Hole and The Shadow and Mass of the Central Black Hole. The goal of the present work is to show that the time-like and null-like geodesics have an anomalous behaviour for a special range of parameters in the dense hair region, defined as Ω(x h ) ≤ r ≤ 2M G N /c 2 . When the geodesics are in the dense hair region, they lose their angular momenta and enter the horizon.