Stationary Scalar Clouds around Kerr-Newman Black Holes

TL;DR

This paper explores the formation of scalar clouds around Kerr-Newman black holes, identifying the role of tachyonic instabilities and the influence of black hole spin on their existence, using numerical spectral methods.

Contribution

It introduces a detailed numerical analysis of scalar cloud modes around Kerr-Newman black holes within the Einstein-Maxwell-scalar framework, highlighting the impact of spin and mode excitation.

Findings

Black hole spin limits scalar cloud existence.

Excited modes need stronger tachyonic instabilities.

Numerical spectral method effectively computes wave functions.

Abstract

This study investigates scalar clouds around Kerr-Newman black holes within the Einstein-Maxwell-scalar model. Tachyonic instabilities are identified as the driving mechanism for scalar cloud formation. Employing the spectral method, we numerically compute wave functions and parameter space existence domains for both fundamental and excited scalar cloud modes. Our analysis demonstrates that black hole spin imposes an upper limit on the existence of scalar clouds, with excited modes requiring stronger tachyonic instabilities for their formation. These findings lay the groundwork for exploring the nonlinear dynamics and astrophysical implications of scalar clouds.