Hydrodynamic Dispersion Relations at Finite Coupling

EasyChair Preprint 10742

Abstract

By using holographic methods, the radii of convergence of the hydrodynamic shear and sound dispersion relations were previously computed in the N=4 supersymmetric Yang-Mills theory at infinite 't Hooft coupling and infinite number of colours. Here, we extend this analysis to the domain of large but finite 't Hooft coupling. To leading order in the perturbative expansion, we find that the radii grow with increasing inverse coupling, contrary to naive expectations. However, when the equations of motion are solved using a qualitative non-perturbative resummation, the dependence on the coupling becomes piecewise continuous and the initial growth is followed by a decrease. The piecewise nature of the dependence is related to the dynamics of branch point singularities of the energy-momentum tensor finite-temperature two-point functions in the complex plane of spatial momentum squared. We repeat the study using the Einstein-Gauss-Bonnet gravity as a model where the equations can be solved fully non-perturbatively, and find the expected decrease of the radii of convergence with the effective inverse coupling which is also piecewise continuous. Finally, we provide arguments in favour of the non-perturbative approach and show that the presence of non-perturbative modes in the quasinormal spectrum can be indirectly inferred from the analysis of perturbative critical points.

Keyphrases: High Energy Physics, Nuclear Theory, strongly correlated electrons

@booklet{EasyChair:10742,
  author    = {Matthew Stephenson and Saso Grozdanov and Andrei Starinets and Peter Tadic},
  title     = {Hydrodynamic Dispersion Relations at Finite Coupling},
  howpublished = {EasyChair Preprint 10742},
  year      = {EasyChair, 2023}}