Fermion perturbations in string-theory black holes

TL;DR

This paper investigates fermion perturbations in four-dimensional string-theory black holes, analyzing their quasinormal modes and late-time decay, revealing similarities with other black hole spacetimes.

Contribution

It provides a detailed analysis of fermion perturbations in specific string-theory black holes, including quasinormal frequencies and decay behavior, using both numerical and semi-analytical methods.

Findings

Quasinormal frequencies calculated via Prony fitting and WKB method.

Fermion fields exhibit late-time decay similar to other four-dimensional black holes.

Decay factors at late times match those of massless fields in known black hole spacetimes.

Abstract

In this paper we study fermion perturbations in four dimensional black holes of string theory, obtained either from a non-extreme configuration of three intersecting five-branes with a boost along the common string or from a non-extreme intersecting system of two two-branes and two five-branes. The Dirac equation for the massless neutrino field, after conformal re-scaling of the metric, is written as a wave equation suitable to study the time evolution of the perturbation. With the aid of Prony fitting of time-domain profile we calculate the complex frequencies that dominate the quasinormal ringing stage, and also determine this quantities by the semi-analytical sixth order WKB method. We also find numerically the decay factor of fermion fields at very late times, and show that the falloff is identical to those appeared for massless fields in other four dimensional black hole spacetimes.