  The holographic duality (also known as AdS/CFT correspondence or
gauge/gravity duality) postulates that strongly coupled quantum field theories
can be described in a dual way in asymptotically Anti-de Sitter space. One of
the cornerstones of this duality is the description of thermal states as black
holes with asymptotically Anti-de Sitter boundary conditions. This idea has led
to valuable insights into such fields as transport theory and relativistic
hydrodynamics. The quasinormal modes of such black holes play a decisive role
and therefore their stability properties are of upmost interest for the
holographic duality. We review recent results using the method of pseudospectra
in this context.
