Grey-body factors for gravitational and electromagnetic perturbations around Gibbons-Maeda-Garfinkle-Horovits-Strominger black holes

TL;DR

This paper derives grey-body factors for gravitational and electromagnetic perturbations around GMGHS black holes, revealing suppression by the dilaton parameter and breaking of iso-spectrality.

Contribution

It provides the first analysis of grey-body factors for gravitons in GMGHS black holes using quasinormal mode data, highlighting dilaton effects.

Findings

Grey-body factors decrease as the black hole charge approaches extremality.

Dilaton field breaks iso-spectrality between axial and polar perturbations.

Grey-body factors are significantly suppressed by the dilaton parameter.

Abstract

While grey-body factors for a test scalar field in stringy black holes described by the renowned Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) solution have been analyzed in the literature, no such analysis exists for gravitons, likely due to the complexity of the perturbation equations. In this study, we utilize known data on quasinormal modes and the relationship between quasinormal modes and grey-body factors to derive these factors for gravitational and electromagnetic perturbations of the dilaton black hole. Our findings indicate that grey-body factors are significantly suppressed by the dilaton parameter as the black hole's charge approaches its extreme value. The iso-spectrality between axial and polar channels of perturbations is broken in the presence of the dilaton field, which leads to different grey-body factors for different types of perturbations.