Speaker: Dr. Benjamin Withers (University of Southampton, UK)
Title: The large-order hydrodynamic series: quasinormal modes and singulants
Abstract: As an effective theory of conserved currents near equilibrium, relativistic hydrodynamics is of wide applicability. However it is formulated as a gradient expansion whose formal properties are poorly understood. I will give an overview of recent developments understanding the large-order behaviour of this expansion and present evidence that it is a divergent series in general. This evidence will be drawn from holography and Israel-Stewart-type models. I will discuss the role played by quasinormal modes and singulants. Singulants obey quasinormal-mode-like dispersion relations and govern the spacetime dependence of the large order behaviour of on-shell constitutive relations.