Joint seminar of the departments “Theory of Fundamental Interactions” and “Theory of Hadronic Matter under Extreme Conditions”

Date and Time: Thursday, 29 July 2021, at 4:00 PM

Venue: online seminar on Zoom, Bogoliubov Laboratory of Theoretical Physics

Seminar topic: “Convergence of hydrodynamic series and dual gravity”

Speaker: A. O. Starinets (The Rudolph Peierls Centre for Theoretical Physics, University of Oxford, UK)

Abstract:

In quantum field theory at finite temperature and density, hydrodynamic modes (e.g. sound waves) are characterised by gapless dispersion relations usually considered as infinite series in powers (or fractional powers) of the spatial momentum squared. These series naturally arise within the classical hydrodynamic gradient expansion understood as an effective theory. Motivated by the search for limits of a reliable hydrodynamic description, we discuss the problem of determining the radii of convergence of such series and its dependence on the coupling. Using dual gravity methods, at least for some theories it is possible to compute the radius of convergence at infinite and large but finite coupling. The obstruction to convergence is caused by the level-crossing phenomenon in the quasinormal spectra of dual black holes. Our calculation shows that the radius of convergence in these theories is a piecewise continuous function of the coupling with an overall tendency to decrease with the coupling decreasing.