  In this paper we consider aspects of the holographic interpretation of
Taub-NUT-AdS$_4$. We review our earlier results which show that TNAdS$_4$ gives
rise to a holographic three-dimensional conformal fluid having constant
vorticity. We then study the holographic relevance of the Misner string by
considering bulk scalar fluctuations. The scalar fluctuations organize
naturally into representations of the $SU(2)\times \mathbb{R}$ isometry
algebra. If we require the string's invisibility we obtain a Dirac-like
quantization relating the frequency of the scalar field modes to the NUT
charge. As the latter quantity determines the total vorticity flux of the
boundary fluid, we argue that such an assumption allows for a holographic
interpretation of TNAdS$_4$ as a {\it non-dissipative} superfluid whose
excitations are quantized vortices. Alternatively, if we regard the Misner
string as a physical object, as has recently been advocated for
thermodynamically, the aforementioned quantization conditions are removed, and
we find that TNAdS$_4$ corresponds to a holographic fluid whose dissipative
properties are probed as usual by the complex quasinormal modes of the bulk
fluctuations. We show that such quasinormal modes are, perhaps surprisingly,
organized into infinite-dimensional non-unitary representations of the isometry
algebra.

High Energy Physics - Theory