Dirac Quasinormal frequencies of the Kerr-Newman black hole

TL;DR

This paper investigates the Dirac quasinormal modes of Kerr-Newman black holes, revealing their complex frequency behavior and spiral patterns as charge and angular momentum vary, using a continued fraction approach.

Contribution

It provides a detailed analysis of the Dirac QNMs of Kerr-Newman black holes, highlighting their frequency trajectories and oscillatory properties with respect to black hole parameters.

Findings

QNMs move counterclockwise in the complex plane with increasing charge or angular momentum.

Frequencies form spiral patterns approaching extremal values.

Oscillations in real and imaginary parts depend on quantum numbers and overtone number.

Abstract

The Dirac quasinormal modes (QNMs) of the Kerr-Newman black hole are investigated using continued fraction approach. It is shown that the quasinormal frequencies in the complex $\omega$ plane move counterclockwise as the charge or angular momentum per unit mass of the black hole increases. They get a spiral-like shape, moving out of their Schwarzschild or Reissner-Nordstr\"om values and "looping in" towards some limiting frequencies as the charge and angular momentum per unit mass tend to their extremal values. The number of the spirals increases as the overtone number increases but decreases as the angular quantum number increases. It is also found that both the real and imaginary parts are oscillatory functions of the angular momentum per unit mass, and the oscillation becomes faster as the overtone number increases but slower as the angular quantum number increases.