Dynamics of test particles around regular black holes in modified gravity (2010.12863v1)

Abstract: In the work, we have presented detailed analyses of the event horizon and curvature properties of spacetime around a regular black hole in modified gravity so-called regular MOG black hole. The motion of neutral, electrically charged and magnetized particles with magnetic dipole moment, in the close environment of the regular MOG black hole immersed in an external asymptotically uniform magnetic field has been also explored. Through the study on the motion of the neutral test particle, we have obtained that the positive (negative) values of the MOG parameter mimic the spin of a rotating Kerr black hole giving the same values for innermost stable pro-grade (retrograde) orbits of the particles in the range of the spin parameter $a/M \in(-0.4125, \ 0.6946)$. The efficiency of energy release from the accretion disk by the Novikov-Thorne model has been calculated and shown that the efficiency is linearly proportional to the increase of the MOG parameter $\alpha$, and exceeds up to 15 \% at the critical limiting value of the MOG parameter $\alpha_{\rm cr}$. The study of the charged particles dynamics has shown that innermost stable circular orbits (ISCOs) of the particle increases with the increase of the MOG parameter, while the increase of cyclotron frequency being responsible to the magnetic interaction causes the decrease of the latter. Moreover, the dynamics of magnetic dipoles has shown that the increase of the MOG and the magnetic coupling parameters lead to an increase of the inner radius and the width of the accretion disk consisting of magnetized particles. Finally, we have focused on showing the range of values of the magnetic coupling parameter causing the orbits to be stable.