You are cordially invited to the SCL online seminar of the Center for the Study of Complex Systems, which will be held on Thursday, 1 April 2021 at 14:00 on Zoom. The talk entitled

Convergence of the gradient expansion in hydrodynamics

will be given by Petar Tadić (Trinity College Dublin, Ireland). Abstract of the talk:

Hydrodynamic excitations corresponding to sound and shear modes in fluids are characterized by gapless dispersion relations. In the hydrodynamic gradient expansion, their frequencies are represented by power series in spatial momenta. In this talk we will discuss the convergence properties of the hydrodynamic series by studying the associated spectral curve in the space of complexified frequency and complexified spatial momentum. For the N=4 supersymmetric Yang-Mills plasma at infinite 't Hooft coupling, we will use the holographic duality methods to demonstrate that the derivative expansions have finite non-zero radii of convergence. Obstruction to the convergence of hydrodynamic series arises from level-crossings in the quasinormal spectrum at complex momenta. Finally, we will discuss how finiteness of 't Hooft coupling affects the radius of convergence.

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