**Publication date:** Jan 2018

**Abstract:**

We investigate particle motion and collisions in the vicinity of

rotating black holes immersed in combined cosmological quintessential

scalar field and external magnetic field. The quintessential dark-energy

field governing the spacetime structure is characterized by the

quintessential state parameter ωq ∈ (-1; -1/3) characterizing its

equation of state, and the quintessential field-intensity parameter c

determining the static radius where the black hole attraction is just

balanced by the quintessential repulsion. The magnetic field is assumed

to be test field that is uniform close to the static radius, where the

spacetime is nearly flat, being characterized by strength B there.

Deformations of the test magnetic field in vicinity of the black hole,

caused by the Ricci non-flat spacetime structure are determined. General

expression of the center-of-mass energy of the colliding charged or

uncharged particles near the black hole is given and discussed in

several special cases. In the case of nonrotating black holes, we

discuss collisions of two particles freely falling from vicinity of the

static radius, or one such a particle colliding with charged particle

revolving at the innermost stable circular orbit. In the case of

rotating black holes, we discuss briefly particles falling in the

equatorial plane and colliding in close vicinity of the black hole

horizon, concentrating attention to the interplay of the effects of the

quintessential field and the external magnetic field. We demonstrate

that the ultra-high center-of-mass energy can be obtained for black

holes placed in an external magnetic field for an infinitesimally small

quintessential field-intensity parameter c; the center-of-mass energy

decreases if the quintessential field-intensity parameter c increases.

**Authors:**

Shaymatov, Sanjar; Ahmedov, Bobomurat; Stuchlík, Zdeněk; Abdujabbarov, Ahmadjon;