#### Presentation Title

Characteristic Orbits of Test Particles Around Regular Black Holes

#### Faculty Mentor

Javlon Rayimbaev

#### Start Date

23-11-2019 10:45 AM

#### End Date

23-11-2019 11:30 AM

#### Location

224

#### Session

poster 4

#### Type of Presentation

Poster

#### Subject Area

physical_mathematical_sciences

#### Abstract

Having applied nonlinear electrodynamics Toshmatov, Stuchilik, and Ahmedov (TAS) obtained their spacetime metric for a nonrotating charged regular black hole (RBH). The purpose of our study was to characterize its properties and dynamical quantities. We characterize the curvature of spacetime through the Ricci and Kretchmann scalars, calculate that the event horizon, r_{EH} , decreases as both the charge of the black hole, *Q*, and degree of nonlinearity, *n*, present in the lapse function, increases, and look at how increasing *n* decreases the maximal charge of the RBH. An analytic expression for the electric field of the RBH from it’s electromagnetic potential, A_{t} , was also obtained. We also consider the innermost stable circular orbit (ISCO) of uncharged particles around the black hole, which is important for describing the accretion disk, and utilize an electromagnetic potential unique to the RBH to study the effective potential and therefore the critical angular momentum for the ISCO of charged particles. We observe that, in general for particles with or without charge, the ISCO radius decreases as *Q* and *n* increases. It is also observed that for particles with sufficiently positive or negative charge, there are two distinctly charged black holes that share the same ISCO radius. The same ISCO radius for two differently charged black holes was also seen in the case of fixing the charge of the particle while varying *n*. In this project, we focused on varying different parameters found through the effective potential to affect the ISCO radius of charged particles, but in general, we wished to flesh out the dynamics of the TAS spacetime metric.

Keywords: regular black hole, nonlinear electrodynamics, effective potential, ISCO, curvature, orbits, lapse function, angular momentum, charged particle

Characteristic Orbits of Test Particles Around Regular Black Holes

224

Having applied nonlinear electrodynamics Toshmatov, Stuchilik, and Ahmedov (TAS) obtained their spacetime metric for a nonrotating charged regular black hole (RBH). The purpose of our study was to characterize its properties and dynamical quantities. We characterize the curvature of spacetime through the Ricci and Kretchmann scalars, calculate that the event horizon, r_{EH} , decreases as both the charge of the black hole, *Q*, and degree of nonlinearity, *n*, present in the lapse function, increases, and look at how increasing *n* decreases the maximal charge of the RBH. An analytic expression for the electric field of the RBH from it’s electromagnetic potential, A_{t} , was also obtained. We also consider the innermost stable circular orbit (ISCO) of uncharged particles around the black hole, which is important for describing the accretion disk, and utilize an electromagnetic potential unique to the RBH to study the effective potential and therefore the critical angular momentum for the ISCO of charged particles. We observe that, in general for particles with or without charge, the ISCO radius decreases as *Q* and *n* increases. It is also observed that for particles with sufficiently positive or negative charge, there are two distinctly charged black holes that share the same ISCO radius. The same ISCO radius for two differently charged black holes was also seen in the case of fixing the charge of the particle while varying *n*. In this project, we focused on varying different parameters found through the effective potential to affect the ISCO radius of charged particles, but in general, we wished to flesh out the dynamics of the TAS spacetime metric.

Keywords: regular black hole, nonlinear electrodynamics, effective potential, ISCO, curvature, orbits, lapse function, angular momentum, charged particle