Linearized hydrodynamics from probe-sources in the gauge-string duality

TL;DR

This paper investigates how localized sources in a strongly coupled plasma influence its hydrodynamic and non-hydrodynamic responses using gauge-string duality, revealing conditions for laminar wakes and breakdown of hydrodynamics.

Contribution

It provides a comprehensive analysis of the plasma's response to various localized sources within the gauge-string duality framework, highlighting the coexistence of hydrodynamic and non-hydrodynamic effects.

Findings

Identification of non-hydrodynamical contributions at leading order

Conditions for laminar wake formation behind sources

Analysis of hydrodynamic breakdown near sources

Abstract

We study the response of an infinite, asymptotically static N=4 plasma to a generic localized source in the probe approximation. At large distances, the energy momentum tensor of the plasma includes a term which satisfies the constitutive relations of linearized hydrodynamics, but it can also include a non-hydrodynamical term which contributes at the same order as viscous corrections, or even at leading order in some cases. The conditions for the appearance of a laminar wake far behind the source and its relevance for phenomenological models used to explain di-hadron correlations are discussed. We also consider the energy momentum tensor near the source, where the hydrodynamical approximation can be expected to break down. Our analysis encompasses a wide range of sources which are localized in the bulk of AdS, including trailing strings, mesonic and baryonic configurations of strings, and point particles.