Remarks on the quasinormal modes of Taub-NUT-AdS$_4$

Abstract

We present results for the numerical evaluation of scalar quasinormal modes in Taub-NUT-AdS$_4$ spacetimes. To achieve this we consider angular modes that correspond to non-unitary highest weight $SU(2)$ representations since global regularity is not consistent with the presence of complex quasinormal modes. We show that for any non-zero value of the NUT charge $n$ there exists a region in the complex plane that contains only stable quasinormal modes. The radius of this region increases with the horizon distance and decreases with $n$ towards a constant value for infinite $n$. We also find analytic and numerical evidence for the existence of a critical NUT charge $n_{cr}$ beyond which the lowest lying stable quasinormal modes become overdamped. Our results draw an intricate picture for the holographic fluid of Taub-NUT-AdS$_4$.