Angular profile of Particle Emission from a Higher-dimensional Black Hole: Analytic Results

TL;DR

This paper analytically investigates the angular distribution of particle emission from higher-dimensional rotating black holes during spin-down, revealing how emission patterns depend on particle type, black hole angular momentum, and extra dimensions.

Contribution

It provides analytical formulas for greybody factors and eigenfunctions, and characterizes the angular emission profiles for fermions, gauge bosons, and scalars in the low-energy regime.

Findings

Gauge bosons align with the rotation axis at low energy.

Fermions form an angle with the rotation axis depending on black hole spin.

Scalar emission shows a spherically symmetric zone followed by equatorial concentration.

Abstract

During the spin-down phase of the life of a higher-dimensional black hole, the emission of particles on the brane exhibits a strong angular variation with respect to the rotation axis of the black hole. It has been suggested that this angular variation is the observable that could disentangle the dependence of the radiation spectra on the number of extra dimensions and angular momentum of the black hole. Working in the low-energy regime, we have employed analytical formulae for the greybody factors, angular eigenvalues and eigenfunctions of fermions and gauge bosons, and studied the characteristics of the corresponding angular profiles of emission spectra in terms of only a few dominant partial modes. We have confirmed that, in the low-energy channel, the emitted gauge bosons become aligned to the rotation axis of the produced black hole while fermions form an angle with the rotation axis whose exact value depends on the angular-momentum of the black hole. In the case of scalar fields, we demonstrated the existence of a "spherically-symmetric zone" that is followed by the concentration of the emission on the equatorial plane, again in total agreement with the exact numerical results.